Plant Saponins

Journal of Ethnopharmacology 94 (2004) 219243

Review

Biological activities and distribution of plant saponinsS.G. Sparg, M.E. Light, J. van Staden

Research Centre for Plant Growth and Development, University of KwaZulu-Natal, Pietermaritzburg, Private Bag X01, Scottsville 3209, South AfricaReceived 9 February 2004; received in revised form 28 May 2004; accepted 29 May 2004

Abstract

Plant saponins are widely distributed amongst plants and have a wide range of biological properties. The more recent investigations andfindings into their biological activities were summarized. Isolation studies of saponins were examined to determine which are the morecommonly studied plant families and in which families saponins have been identified. 2004 Elsevier Ireland Ltd. All rights reserved.

Keywords: Plant saponins; Triterpenoid; Steroidal; Biological activity; Distribution

1. Introduction

Saponins are a vast group of glycosides, widely distributedin higher plants. Their surface-active properties are whatdistinguish these compounds from other glycosides. Theydissolve in water to form colloidal solutions that foam uponshaking (Tyler et al., 1981). Saponin containing plants aresought after for use in household detergents (sapo, onis= soap) (Bruneton, 1995). One such example is the soapwort(Saponaria officinalis L.), which has been widely used forcenturies. Saponins have also been sought after in the phar-maceutical industry because some form the starting pointfor the semi-synthesis of steroidal drugs. Many have phar-macological properties and are used in phytotherapy and inthe cosmetic industry. They are believed to form the mainconstituents of many plant drugs and folk medicines, andare considered responsible for numerous pharmacologicalproperties (Estrada et al., 2000). Liu and Henkel (2002)consider saponins and polyphenols key ingredients in tradi-tional Chinese medicines, and are responsible for most ofthe observed biological effects. For example, the ginsengroot (Panax ginseng C.A.Meyer, Araliaceae) is one of the

Abbreviations: CDDP, cisplatin; ED50, median effective dose; HD50,haemolytic dose of 50%; HD100, haemolytic dose of 100%; HGF, humangingival fibroblasts; HIV, human immunodeficiency virus; HSC, humanoral squamous cell carcinoma; HSV, anti-herpes simplex virus; IC50,median inhibitory concentration; LC50, median lethal concentration; LD50,median lethal dose; LD90, lethal dose at 90%; LD95, lethal dose at 95%;MIC, minimum inhibitory concentration; TGF, transforming growth factor Corresponding author. Tel.: +27 33 260 5130; fax: +27 33 260 5897.E-mail address: [email protected] (J. van Staden).

most important traditional oriental medicines and is nowused worldwide (Fukuda et al., 2000). Saponins are said tomake up the active major constituents of ginseng. The genusBupleurum is officially listed in Chinese and Japanese Phar-macopoeias are used in Asian traditional medicines to treatdifferent ailments. The dry roots of Bupleurum fruticescensL. (Apiaceae) are traditionally used to treat disorders asso-ciated with inflammation. The main anti-inflammatory com-pounds found in Bupleurum fruticescens are saikosaponins(Just et al., 1998). Active constituents of Allium chinenseG.Don and Allium macrostemon Bunge (Alliaceae) the mainsources of a Chinese Traditional medine Xiebai whichused as a treatment for chest pain, stenocardia and cardiacasthma have been shown to be saponins (Baba et al., 2000).

Most saponins have haemolytic properties and are toxicto most cold-blooded animals. The seeds of Barringtoniaasiatica Kurz (Lecythidaceae) which have known to con-tain saponins, have been used traditionally by native Asianand Pacific fisherman for centuries to enhance their catches(Herlt et al., 2002). However, since these properties arenot common to all saponins, they cannot be distinguishedfrom other compounds on the basis of these properties alone(Bruneton, 1995).

Saponins can be classified into two groups based on thenature of their aglycone skeleton. The first group consistsof the steroidal saponins, which are almost exclusivelypresent in the monocotyledonous angiosperms. The secondgroup consists of the triterpenoid saponins, which are themost common and occur mainly in the dicotyledonous an-giosperms (Bruneton, 1995). Some authors distinguish athird group called steroidal amines, which are classified by

0378-8741/$ see front matter 2004 Elsevier Ireland Ltd. All rights reserved.doi:10.1016/j.jep.2004.05.016

220 S.G. Sparg et al. / Journal of Ethnopharmacology 94 (2004) 219243

Fig. 1. Aglycone skeletons of (A) steroidal spirostane, (B) steroidalfurostane, and (C) triterpenoid saponins. R = sugar moiety.

others as steroidal alkaloids (Bruneton, 1995). For the pur-pose of this review, only steroidal and triterpenoid saponinswere considered. Steroidal saponins consist of a steroidalaglycone, a C27 spirostane skeleton, generally comprisingof a six-ring structure (Fig. 1A). In some cases, in freshplant material, the hydroxyl group in the 26-position is en-gaged in a glycosidic linkage, and so the aglycone structureremains pentacyclic. This is referred to as a furostane skele-ton (Fig. 1B). Triterpenoid saponins consist of a triterpenoidaglycone, which consists of a C30 skeleton, comprising of apentacyclic structure (Fig. 1C). According to Haralampidiset al. (2002), very little is known about the enzymes andbiochemical pathways involved in saponin biosynthesis inplants. Haralampidis et al. (2002) review the biosynthesis oftriterpenoid saponins and addressed recent advances in twokey areas of saponin biosynthesis, namely the glycosylationof sapogenins and the cyclisation of 2,3-oxidosqualene.

Biological and pharmacological activities of saponinshave been reported in several reviews with the most re-cent being Lacaille-Dubois and Wagner (1996). Similarly,this review will also summarize some of the importantreports of biological active plant saponins of recent years(19982003) and will discuss the taxonomic distribution ofrecently isolated saponins.

2. Biological and pharmacological properties ofsaponins

2.1. Haemolytic activity

Saponins have the ability to rupture erythrocytes. This haslead to the development of the haemolytic assays for detect-ing the presence of saponins in drugs or plant extracts. The

haemolytic properties are generally attributed to the interac-tion between the saponins and the sterols of the erythrocytemembrane. As a result, the membrane bursts, causing an in-crease in permeability and a loss of haemoglobin. Baumannet al. (2000) investigated the effect of saponins on the mem-brane structure through haemolysis of human erythrocytes.The findings showed that saponin-lysed erythrocytes do notreseal, and therefore indicates that saponin damage to thelipid bilayer is irreversible.

Oda et al. (2000) reported on the haemolytic activity of47 different plant derived saponins, purified from food andmedicinal plants. It has been suggested that there is a re-lationship between the adjuvant and haemolytic activity ofsaponins, however, the results indicated that the adjuvant ac-tivity does not relate with haemolytic activity. A substanceor compound is said to have adjuvant activity if when usedwith another active compound, it enhances the activity ofthe active compound. The level of haemolytic activity wasattributed to the type of aglycone and the presence of sugarside chains. Saponins with an acyl residue or oxide-ringmoiety tended to show haemolytic activity, except for labla-boside D, which did not show haemolytic activity despitepossessing a acyl residue. Escin saponins found in Aescu-lus hippocastanum L. (Hippocastanaceae) and jujubosidesaponins from Zizyphus jujuba Mill. (Rhamnaceae) hadstrong haemolytic activity.

Sindambiwe et al. (1998) tested a mixture of saponinsisolated from Maesa lanceolata Forssk. (Myrsinaceae) forhaemolytic activity. The maesasaponin mixture, showedvery high haemolytic activity, haemolysing 50% of thehuman erythrocytes (1% suspension in phosphate buffersaline) at a concentration of 1.6g/ml. Apers et al. (2001)also tested 10 novel saponins isolated from Maesa lanceo-lata for haemolytic activity. Some of the saponins showedno activity while others possessed very strong haemolyticactivity. A number of structureactivity relationships wereestablished and it was concluded that in the case of mae-sasaponins, substitution at position C-22 appears to be anessential structural feature for high haemolytic activity.

An oleanolic saponin mixture showed higher haemolyticactivity than a dialysed reference saponin mixture fromMerck (HI 30 000) (Voutquenne et al., 2003). The saponinswere isolated from the stem bark of Pometia ridleyi Kingemend. Radlk. (Sapindaceae). However, the quantities ofpure saponins were insufficient to test individual haemolyticactivities of each compound. Instead a saponin mixturewas tested on sheep erythrocytes (10% suspension in phos-phate buffer saline). A 70% haemolysis was obtained at25g/ml. The HD100 was obtained at 50g/ml and HD50was estimated at 23g/ml.

Ahn et al. (1998) investigated the inhibitory effect ofBupleurum falcatum L. (Apiaceae) saponins on anti-celladhesive activity and its relation to haemolytic action.Saikosaponins-A, -D and -E were isolated and exhibitedpotent anti-cell adhesive activity and a strong haemolytic ac-tion. From the results, it was suggested that the mechanism

S.G. Sparg et al. / Journal of Ethnopharmacology 94 (2004) 219243 221

for anti-cell adhesive activity may resemble that for thehaemolytic action.

2.2. Molluscicidal activity

Although toxic to cold-blooded species, if taken orallyby warm-blooded species, saponins have only a weak tox-icity (Bruneton, 1995), which is probably attributed to lowabsorption rates. The toxicity towards cold-blooded specieshas lead to the use of saponin containing drugs to catch fish.

Saponins are also highly toxic to molluscs and have beeninvestigated as molluscicides in the control of schistosomi-asis (Sindambiwe et al., 1998; Abdel-Gawad et al., 1999).Bulinus and Biomphalaria species in particular, act as in-termediate hosts in the life cycle of schistosomes, whichcause urinary bilharzia. Many trials have been run in Africancountries where schistosomiasis has a high prevalence. Ina study by Sindambiwe et al. (1998) a six-oleanane-typetriterpenoid saponin mixture (maesasaponin mixture, iso-lated from Maesa lanceolata) was tested for molluscicidalactivity against Biomphalaria glabrata. The saponin mix-ture showed high toxicity, with LD95 and LD50 values of4.1 and 2.3g/ml, respectively.

Phytolacca dodecandra LHr. (Phytolaccaceae) andPhytolacca icosandra L. berries contain saponins withhighly potent molluscicidal activity (Treyvaud et al., 2000).Aqueous extracts (25g/ml) of Phytolacca icosandra hada very high molluscicidal activity against Biomphalariaglabrata snails. According to Treyvaud et al. (2000), the ac-tivity can be attributed to the presence of monodesmosidicsaponins of serjanic and spergulagenic acids. Mlgaardet al. (2000) investigated the biodegradability of molluscici-dal water-extracted saponins from the berries of Phytolaccadodecandra. Results showed that the saponins in an aque-ous extract of Phytolacca dodecandra readily biodegraded(t1/2 = 15.8 h). The saponins were completely consumedwithin 10 days which indicates their abilities to degrade inaquatic environments under aerobic conditions. As a result,the use of Phytolacca dodecandra berries for snail controlin schistosomiasis-infested water bodies is environmentallyacceptable.

Apers et al. (2001) tested 10 saponins isolated from theleaves of Maesa lanceolata for molluscicidal activity againstBiomphalaria glabrata snails. The LC50 value of the saponinmixture was 1.25 mg/ml. However, it was concluded thatone of the saponins, maesasaponin VI2 is responsible for alarge part of the activity of the mixture. This saponin had aLC50 value of 0.5 mg/ml in its isolated form.

Triterpenoid hederagenin saponins isolated from Sapindusmukorossi Gaertn. (Sapindaceae) had molluscicidal effectsagainst the golden apple snail, Pomacea canaliculata, whichhave become major pests of rice and other aquatic cropsthroughout Taiwan and other parts of Asia (Huang et al.,2003). Seven isolated hederagenin saponins, including onenew hederagenin saponin, hederagenin 3-O-(2,4-O-di-acetyl--l-arabinopyranoside)-(1 3)--l-rhamnopyranosyl-(1

2)--l-arabinopyranoside, resulted in 70100% mortal-ity at 10 ppm against the golden apple snails. Hederageninsaponins with three sugar moieties had higher molluscicidalactivity than triterpene saponins with one sugar moiety.

2.3. Anti-inflammatory activity

There are a number of reports of saponins withanti-inflammatory properties. Many saponins isolated fromplant sources produce an inhibition of inflammation in themouse carrageenan-induced oedema assay. In a study byJust et al. (1998), Fruticesaponin B, a bidesmosidic saponinwith an unbranched saccharide moiety isolated from Bu-pleurum fruticescens L. (Apiaceae), was shown to have thehighest anti-inflammatory activity of the all the saponinstested in the mouse oedema assays. Just et al. (1998)suggested that the anti-inflammatory activity of saponinsisolated from Bupleurum fruticescens is related to the chem-ical structure of the saponins. In vivo studies on saponinsisolated from Bupleurum rotundifolium L. (Apiaceae) werereported to have anti-inflammatory activity against both12-O-tetradecanoylphorbol-13-acetate (TPA) induced earoedema and chronic skin inflammation (Navarro et al.,2001). Of the seven saponins tested, five were fairly activein reducing the TPA-induced ear oedema. The saponinsproduced a dose-dependent oedema reduction. Only twosaponins were active in reducing the chronic skin inflam-mation, and also caused a parallel decrease in neutrophileinfiltration.

Aescin, a mixture of triterpenoid saponins that forms themajor active principle of Aesculus hippocastanum L. (Hip-pocastanaceae), has been shown to have anti-inflammatory,anti-oedematous and venotonic properties (Sirtori, 2001).

Li et al. (2002) isolated two triterpenoid saponins fromthe stem bark of Kalopanax pictus Nakai (Araliaceae). Bothkalopanaxsaponin A and pictoside A were isolated andshowed significant anti-inflammatory activity at the oraldose of 50 mg/ml.

A novel steroidal saponin isolated from the leaves ofAgave attenuata Salm-Dyck (Agavaceae) was evaluated foranti-inflammatory activity using the capillary permeabilityassay (da Silva et al., 2002). The steroidal saponin inhibitedthe increase in vascular permeability caused by acetic acidwhich is a typical model for the first stage inflammatory re-action. However, the activity was not accompanied by anundesirable haemolytic effect and warrants further investi-gation as an anti-inflammatory drug.

The triterpenoid saponin loniceroside C isolated from theaerial parts of Lonicera japonica Thunb. (Caprifoliaceae),a medicinal plant known as an anti-inflammatory agent forcenturies, showed anti-inflammatory activity when testedin vivo in the mouse ear oedema provoked by croton oil(Kwak et al., 2003). Loniceroside C inhibited the ear oedema(1531%) at concentrations ranging from 50200 mg/kg.

Kim et al. (1998a) investigated the anticomplementaryactivity of ginseng (Panax ginseng C.A. Mey., Araliaceae)


saponins. Ginsenoside Ro and oleanolic acid showed thehighest anticomplementary activity of the tested saponins.Kim et al. (1998a) suggested that the anti-inflammatory ac-tivity of these saponins is related to anticomplementary ac-tion through the classical inflammation pathway.

2.4. Antifungal/antiyeast activity

Sindambiwe et al. (1998) tested a maesasaponin mixtureisolated from Maesa lanceolata for its fungistatic activity.The mixture inhibited the growth of Epidermophyton flocco-sum, Microides interdigitalis and Trichophyton rubrum at aconcentration of 50g/ml. Candida albicans and Microspo-rum canis growth was inhibited at 100g/ml. The develop-ment of Microsporum langeroni was inhibited at 250g/ml.No fungicidal activity was shown at lower concentrationsup to 1g/ml.

Saponins isolated from Panax notoginseng (Burk.)F.H.Chen (Araliaceae) were reported to exhibit an inhibitoryeffect on Aphanomyces cochlioides zoospore motility (Maet al., 1999). Seven of the 14 saponins tested had an in-hibitory effect on zoospore motility.

Li et al. (1999b) tested three jujubogenin saponinsisolated from Colubrina retusa L. (Rhamnaceae) forantifungal activity against Candida albicans, Crytococ-cus neoformans and Aspergillus fumigatus. The knownsaponin, jujubogenin [3-O--l-arabinofuranosyl-(1 2)--d-glucopyranosyl-(1 3)]--l-arabinopyranoside,showed modest growth-inhibitory effects with a MIC of50g/ml against all three test cultures. Of the two new mi-nor jujubogenin saponins isolated only one was marginallyactive with growth-inhibitory effects only against Crytococ-cus neoformans (MIC = 50g/ml).

In a study by Bader et al. (2000) it was shown that antifun-gal activity of saponins against different Candida albicansstrains can be influenced by the variation of the etherglyco-sidically bonded carbohydrate units and the acylglycosidi-cally bonded oligosaccharide at C-28 of the aglycone.

Steroidal saponins from Yucca schidigera Roezl.ex Ortgies (Agavaceae) (Mohave yucca) were shownto exhibit effective growth-inhibitory activities againstfood-deteriorating yeasts, film-forming yeasts, and dermato-phytic yeasts and fungi (Miyakoshi et al., 2000). A saponinfraction, containing mainly monodesmosidic saponins, wastested for both antiyeast and antifungal activity. The saponinfraction showed growth-inhibitory activity against manyof the yeasts, as well as some dermatophytic fungi (MICvalues ranged between 31.3 and 125g/ml).

Eight previously characterized monodesmosidic saponinsisolated from Hedera colchica K.Koch (Araliaceae) weretested for antifungal and antiprotozoal activity (Mshvildadzeet al., 2000). Although the compounds exhibited antifungalactivity, the activity was lower than those of the referenceantifungal agents. However, even though the activity waslow, there was a clear indication that the antifungal activitywas structure related. Saponins with hederagenin as their

aglycone were more active than those without. The number,kind and sequence of the sugar residues also had a significanteffect on the antifungal activity observed.

Triterpenoid saponins from the seeds of Chenopodiumquinoa Willd. (Chenopodiaceae) have been reported to haveantifungal activity (Woldemichael and Wink, 2001). Onlythe crude saponin mixture inhibited the growth of Candidaalbicans at 50g/ml. The pure compounds showed littleor no activity, which suggests a possible synergistic effectbetween these saponins.

Furostanol saponins isolated from the seeds of Capsicumannuum L. var. acuminatum Fingerh. (Solanaceae) showedstronger antiyeast activity than antifungal activity (Iorizziet al., 2002). Three new furostanol saponins, capsicosidesE, F and G, and seven oligoglycosides were isolated andtested for both antifungal and antiyeast activity. AntifungalMIC values ranged from 125g/ml to >1000g/ml and an-tiyeast MIC values from 12.5 to 10g/ml. However, whentesting for novel pharmacological compounds, MIC valuesof >1000g/ml are generally too weak be considered activeand should rather be reported as not active.

Many different species of the genus Phytolacca (Phyto-laccaceae) also contain saponins that show antifungal ac-tivity (Quiroga et al., 2001; Escalante et al., 2002). Threeolean-type triterpenoid saponins isolated from the berries ofPhytolacca tetramera Hauman (Phytolaccaceae) were testedfor antifungal activity (Escalante et al., 2002). Two of thesaponins, phytolaccosides B and E showed antifungal activ-ity against the human pathogenic opportunistic fungi. Phy-tolaccoside B had the broadest spectrum of activity againstthe fungi tested.

CAY-1, a steroidal saponin isolated from the fruits of Cap-sicum frutescens L. (Solanaceae) was shown to be a potentfungicide and antiyeast properties (de Lucca et al., 2002).The saponins had LD90 values between 3 and 20M againstvarious Aspergillus species and IC50 values of 9.5M and6.2M against Pneumocystis carinii and Candida albicans,respectively. The results indicated that CAY-1 could proveto be an effective fungicide, at concentration levels that hadno cytotoxic activity on A 549 lung carcinoma and HeLacell lines.

Five new spirostanol saponins and two sterol gly-cosides isolated from Solanum chrysotrichum Schldh.(Solanaceae) leaves were tested for their antifungal activities(Zamilpa et al., 2002). One of the new spirostan saponins,6-O--d-xylopyranosyl-(1 3)--d-quinovopyranosyl-(25R)-5-spirostan-3,23-ol, was the most active sub-stance with MIC values of 100 and 200g/ml againstAspergillus niger and Candida albicans, respectively, and12.5g/ml for both Trichophyton mentagrophytes and Tri-chophyton rubrum.

2.5. Antibacterial/antimicrobial activity

Saponins have also been reported to have antimicrobialactivity (Killeen et al., 1998). Three butanol-extractable


5-spirostan-3-ol saponins were shown to have antimicro-bial activity on both prokaryotic and eukaryotic organisms,but only at low cell densities. The saponins did not inhibitmicrobial growth of dense populations.

Three new triterpenoid saponins, Nudicaucins A, B, and Cand a known saponin guaiacin D were isolated from Hedyotisnudicaulis Wight & Arn. (Rubiaceae) were tested againstBacillus subtilis (Konishi et al., 1998). All four of the iso-lated saponins showed weak antibacterial activity. Resultsindicated that the tetraglycoside saponins have stronger ac-tivity than the triglycoside saponins.

A new jujubogenin saponin isolated from Colubrinaretusa L. (Rhamnaceae), jujubogenin 3-O--l-arabinofura-nosyl-(1 2)-[3-O-(trans)-p-coumaroyl--d-glucopyrano-syl-(1 3)]--l-arabinopyranoside, had antimycobacterialactivity when tested against Mycobacterium intracellu-lare (ElSohly et al., 1999). The jujubogenin saponin hadantimycobacterial activity at a MIC of 10g/ml.

Iorizzi et al. (2002) isolated three new furostanol saponinsalong with seven known saponins from the seeds of Cap-sicum annuum L. var. acuminatum Fingerh. (Solanaceae).The saponins showed weak or no growth inhibition againstboth Gram-positive and Gram-negative bacteria (MIC>1000g/ml).

2.6. Antiparasitic activity

Two new triterpenoid saponins, glinoside A and B,isolated from the aerial parts of Glinus oppositifolius L.(Molluginaceae) were shown to have antiprotozoal activ-ity against Plasmodium falciparum (Traore et al., 2000).Results showed that the saponin fractions had slightly bet-ter antiplasmodial activity (IC50 of 31.8g/ml) than pureglinoside A (IC50 of 42.3g/ml).

Three saponins isolated from Hedera helix L. (Arali-aceae), - and -hederin and hedeacolchiside A1, wereshown to have antileishmanial activity (Delmas et al.,2000). The results showed that these saponins exhibited astrong antiproliferative action on all the stages of devel-opment of the parasite Leishmania infantum. The actionof the saponins was due to changes in membrane integrityand potential. Hederacolchiside A1 had the strongest ac-tivity against both promastigote (IC50 of 1.2 0.1M)and amastigote (IC50 of 0.053 0.002M) form of theparasite. The same saponins also exhibited potent antipro-liferative activity against human monocytes as a result ofsignificant DNA synthesis inhibition. The findings suggestthat these saponins could be considered as possible futureantileishmanial drugs.

2.7. Cytotoxicity and antitumor activity

Numerous reports highlight the highly cytotoxic proper-ties of many saponins. However, saponins with high cytotox-icity do not always have antitumor properties as cytotoxiccompounds can potentially be used as antitumor agents.

A novel steroidal saponin, furcreastatin, isolated from anethanolic extract of the leaves of Furcraea foetida (L.) Haw.(Agavaceae) was screened for its selective cytotoxicity to-wards mutant p53-expressing mouse fibroblasts (Itabashiet al., 1999). Furcreastatin consists of a hecogenin aglyconewith a hexasaccharide containing d-galactose, l-rhamnoseand four d-glucose residues. The compound decreased theviability of mutant p53-overexpressing cells with an ED50of 4g/ml. Furcreastatin was also reported to be cytotoxicagainst parental cell-lines (ED50 of 9.6g/ml).

Many isolated steroidal saponins have been shown to beeither cytostatic or cytotoxic to HL-60 human leukemia celllines (Mimaki et al., 1998b, 1998c, 1999a, 1999c, 2001b;Yokosuka et al., 2002b). Mimaki et al. (1998b) tested 11 newsaponins isolated from Ruscus aculeatus L. (Liliaceae). Onlytwo of these saponins, ruscogenin diglycoside (spirostanolsaponin) and its corresponding 26-glycosyloxyfurostanolsaponin showed cytostatic activity at 10g/ml (IC50 values3.1 and 3.7g/ml, respectively).

Mimaki et al. (1999c) also tested nine steroidal saponins,including five new saponins, isolated from the aerial partsof Dracaena draco L. (Dracaenaceae) for their cytostaticactivities. Only two of the tested saponins showed relativelypotent cytostatic activity against the human promyelo-cytic leukemia HL-60 cells. Only one of the new sapon-ins, (23S,24S)-spirosta-5,25(27)-diene-1,3,23,24-tetrol1-O-[O-(2,3,4-tri-O-acetyl--l-rhamnopyranosyl)-(1 2)--L-arabinopyrano-syl]24-O--D-fucopyranoside, and theknown compound, (25R)-spirost-5-en-3-ol3-O-[O--l-rhamnopyranosyl-(1 2)--d-glucopyranoside], had cyto-static activities with IC50 values of 2.6g/ml and 1.3g/ml,respectively. Tran et al. (2001b) tested spirostanol andfurostanol type saponins from the roots and rhizomes ofDracaena angustifolia Roxb. (Dracaenaceae) for antipro-liferative activity against murine colon 26-L5 carcinoma,human HT-1080 fibrosarcoma, and B-16 BL6 melanomacells. Three of the tested compounds showed potent an-tiproliferative activity against HT-1080 fibrosarcoma cells(IC50 values from 0.2 to 0.6M). Draconins A, B and C,three new steroidal saponins, were isolated from the stembark of Dracaena draco along with 17 known compounds(Gonzlez et al., 2003). Several of the isolated compoundsshowed potent cytotoxic activity against the human leukemiacell line HL-60 (IC50 values from 2.0 to 9.7M at 72 h).

Triterpenoid saponins have also shown cytotoxicityagainst human cell lines. A novel triterpene saponin, iso-lated from the root bark of Aralia dasyphylla Miq. (Arali-aceae) showed significant cytotoxic activity against KB andHeLa-S3 cells (Xiao et al., 1999). The IC50 values were1.2g/ml for KB cells and 0.02g/ml for HeLa-S3 cells.

Lee et al. (1999) isolated a novel saponin metabolite(IH-901) from Panax ginseng C.A.Meyer (Araliaceae),which showed in vitro antitumor activity. This compoundwas tested against four human cancer cell lines and onesubline resistant to cisplatin (CDDP). From the results itwas suggested that this saponin was not cross-resistant to


CDDP in the tested cell line and could be a candidate forthe treatment of CDDP resistant pulmonary cancer. Gin-seng saponins isolated from Panax ginseng C.A.Meyer(Araliaceae) and their cancer preventing activities werereviewed by Shibata (2001). It was concluded that ginseno-side, tetracyclic dammarane-type triterpenoid saponins canbe administered safely as anticancer agents due to theirnon-toxic and non-haemolytic properties. Yun (2003) alsoinvestigated the anticancer properties of Panax ginsengC.A.Meyer (Araliaceae). From the study it was concludedthat the activity of ginseng saponins are non-organ specificand that the anticarcinogenicity or human cancer preven-tative effect of Panax ginseng is due to the ginsenosidesaponins Rg3, Rg5 and Rh2.

Mimaki et al. (1999a) tested nine triterpene saponins iso-lated from the roots of Pulsatilla chinensis (Bunge) Regel(Ranunculaceae) for their cytotoxic activity. All the saponinstested exhibited moderate cytotoxic activity with IC50 val-ues ranging from 2.3 to 7.8g/ml, with exception of onesaponin which had no substituent at C-2 of the arabinosylmoiety attached to the aglycone. The results of the test-ing suggested that the glycoside moiety attached at the C-3of the aglycone is essential for cytotoxic activity from thesaponins evaluated.

Cytotoxic triterpenoid saponins were isolated from amethanol extract of the aerial parts of Trevesia palmata(Roxb. ex Lindl.) Vis. (Araliaceae) (De Tommasi et al.,2000). Six new bisdemosidic saponins, along with two knowtriterpenoid saponins, were tested for their antiproliferativeactivities against three continuous culture cell lines (J774,HEK-293 and WEHI-164). Results of this investigationshowed that the hydroxyl group at C-28 and the saccharidechain esterified at C-28 play an important role in mediatingantiproliferative activity.

Two new triterpenoid saponins isolated from the roots ofAcanthophyllum squarrosum Boiss. (Caryophyllaceae) weretested in vitro for lymphocyte antiproliferation (Gaidi et al.,2000b). The results revealed one of the saponins to have amoderate concentration-dependent cytotoxic effect on lym-phocytes in culture. The same saponin was not cytotoxicto lymphocytes up to a concentration of 10g/ml, althoughhigher concentrations showed strong cytotoxicity.

Ginseng (Panax ginseng C.A.Meyer, Araliaceae) saponinswere shown to have antiproliferative effects on humanprostate cancer cell lines (Liu et al., 2000). One of thetested ginsenosides, ginsenoside Rg3, displayed growth in-hibitory activity against human prostate carcinoma LNCaPcells. The ginsenoside Rg3 activated the expression ofcyclin-kinase inhibitors, p21 and p27, arrested LNCaP cellsat the G1 phase, and subsequently inhibited tumor cellgrowth through a caspase-3-mediated apoptosis mechanism.

Qiu et al. (2000) isolated the saponin chloromaloside Afrom Chlorophytum malayense Ridl. (Liliaceae), which wasfound to be highly cytotoxic. In vitro studies showed thissteroidal saponin to have cytotoxicity against human cancercell lines.

Julibroside J1 and Julibroside J9, two diastereomericsaponins isolated from the stem bark of Albizia julibrissinDurazz. (Leguminosae), showed cytotoxic activity (Zouet al., 2000). Both saponins showed good inhibitory actionagainst the KB cancer cell lines in vitro. Abdel-Kader et al.(2001) tested two isolated saponins from a methanol extractof Albizia subdimidiata (Splitg.) Barneby & J.W. Grimes(Leguminosae) for their cytotoxic activity. Both saponinsshowed significant cytotoxicity against A2780 cells. Oneof the compounds, albiziatrioside A, is a new triterpenoidsaponin and had an IC50 value of 0.9g/ml.

In a study by Yokosuka et al. (2000a) nine isolatedsteroidal saponins, including three new bisdesmosidicspirostanol saponins, surculosides A, B and C and one bis-desmosidic furostanol saponin, were tested for cytotoxicactivity against HL-60 human promyelocytic leukemia cells.Only the three known saponins of the nine tested, showedweak cytotoxic activity with their IC50 values ranging from4.2 to 8.7g/ml.

Eight steroidal saponins isolated from Allium porrum L.(Alliaceae) were found to be cytotoxic to WEHI 164 cells(IC50 values from 1.9 to 21.1g/ml) and J774 cells (IC50values from 2.1 to 27.9g/ml) (Fattorusso et al., 2000).Three of the tested saponins had IC50 values below 6g/mlagainst both cell lines. Baba et al. (2000) showed saponinsisolated from another Allium species, Allium chinenseG.Don (Alliaceae), to have antitumor-promoting activity ina two-stage lung carcinogenesis experiment.

Two triterpene saponins, securioside A and securioside B,were isolated from a saponin fraction of an aqueous extractof Securidaca inappendiculata Hassk. (Polygalaceae) roots(Yui et al., 2001). The saponin fraction inhibited macrophagegrowth as a result of a cytotoxic effect. It was suggested thatthese two saponins are essential for the cell death-inducingactivity of the aqueous extract.

Dong et al. (2001a, 2001b) showed steroidal saponins iso-lated from Dioscorea panthaica Prain & Burkill (Dioscore-aceae) to be cytotoxic to A375-S2, L929 and HeLa cell lines.All seven of the isolated saponins tested had cytotoxic ac-tivities against the three cell lines (Dong et al., 2001a). TheIC50 values ranged from 8.4 to 2.2g/ml against A375-S2cells, 8.6 to 1.8g/ml against L929 cells and 7.9 to 2.1g/mlagainst HeLa cell line. Dioscin, a known saponin had themost potent cytotoxic activity against all the cell lines (Donget al., 2001a).

Saponins isolated from Camassia leichtlinii (Bak.) S.Wats. (Liliaceae) have been shown to have cytotoxic activityagainst human oral squamous cell carcinoma (HSC-2) cellsand normal human gingival fibroblasts (Kuroda et al., 2001).

Hederagenin, o-hederin, kalopanaxsaponin A (commonlyknown as -hederin), kalopanaxsaponin I, and sapindoside Cwere isolated from the stem bark of Kalopanax pictus Nakai(Araliaceae) (Park et al., 2001). These saponins were testedfor their cytotoxicity against different types of tumor cells.The results indicated that kalopanaxsaponin A has potentialantitumor applications. In vivo studies on antitumor activity


by ethanol extracts of Nigella sativa L. (Ranunculaceae)seeds have shown the principle bioactive compound to be-hederin, a monodesmosidic triterpene saponin (Kumaraand Huat, 2001).

Mimaki et al. (2001a) tested steroidal saponins isolatedfrom the leaves of Cestrum nocturnum L. (Solanaceae) fortheir cytotoxic activities against human oral squamous cellcarcinoma (HSC-2) cells and normal human gingival fibrob-lasts (HGF). The steroidal saponins exhibited considerablecytotoxicity against HSC-2 cells, with LD50 values rang-ing from 2.0 to 13g/ml. Three of the saponins showed510-fold higher cytotoxic activities against HSC-2 cellsthan against HGF. However, two compounds were cyto-toxic against both HSC-2 cells and HGF. Mimaki et al.(2001a) concluded that the structure of the sugar portion ofthese steroidal saponins appears to play an important role intumor-specific cytotoxicity.

Mimaki et al. (2001b) systematically examined the cyto-toxic activities of a number of steroidal saponins isolatedfrom plants of the Liliaceae family. Some of the saponinsshowed potent cytotoxic activity against HL-60 humanpromyelocytic leukemia cells. The cytotoxic activity wasfound to be linked to the monosaccharides constitutingthe sugar moieties and their sequences, as well as to thestructure of the aglycones.

Hederacolchiside A1, a new oleanolic acid monodesmo-side isolated from Hedera colchica K.Koch (Araliaceae)demonstrated strong cytotoxicity activities on a number ofcancer cells (IC50 from 4.5 to 12M) (Barthomeuf et al.,2002). The antiproliferative effects on the different cancerlines suggests that despite the lack of specificity for cancercells, hederacolchiside A1 has potential antitumor applica-tions.

Triterpene saponins isolated from Silene fortunei Vis.(Caryophyllaceae) were shown to increase the accumulationand cytotoxic activity of the anticancer agent cisplatin onhuman colon tumor cells (Gaidi et al., 2002). On their own,the saponins did not have significant cytotoxic activities.

Four new steroidal saponins were isolated from rhizomesof Tacca chantrieri Andr (Taccaceae) (Yokosuka et al.,2002b). The isolated compounds were evaluated for theircytotoxic activity against HL-60 human promyelocyticleukemia cells. One of these compounds showed consid-erable cytotoxicity (IC50 of 1.8M). Two other saponins,which were structurally related to the active saponin, didnot show cell growth inhibitory activity when tested at10g/ml. These findings suggest that both the aglyconestructure and the sugar moieties contribute to the cytotoxic-ity activity of the saponins. Even slight structural differencescan affect the activity.

Seo et al. (2002b) isolated three new saponins and threeknown saponins from Acacia tenuifolia (L.) Willd. (Legu-minosae) using bioassay-guided fractionation. The saponinsshowed weak activity against the genetically engineered Sac-charomyces cerevisiae mutant (1138, 1140, 1353 and Sc-7)yeast strains tested. Two of the known saponins, which were

previously isolated by Abdel-Kader et al. (2001), showedsignificant cytotoxic activity against M 109 lung cancercell lines, with IC50 values of 1M. The new saponins hadweak activity against the A 2780 ovarian cancer cell lines.Another Acacia species, Acacia victoriae Benth. (Legu-minosae), contains saponins with tumor-inhibitory activity(Jayatilake et al., 2003). Two new saponins, Avicins D andG, were isolated from the seedpods of Acacia victoriae.Both compounds showed potent cytotoxic activity againsthuman T-cell leukemia (Jurkat cells) in vitro. Avicin D andAvicin G had IC50 values of 0.58g/ml and 0.22g/ml,respectively. Mujoo et al. (2001) investigated the antiprolif-eration effect of triterpenoid saponins isolated from Acaciavictoriae. The saponins and avicins markedly inhibited thegrowth of several tumor cell lines with low growth inhibi-tion in human foreskin fibroblasts, mouse fibroblasts andimmortalized breast epithelial cells at similar concentra-tions. Hanausek et al. (2001) tested the ability of avicinsaponins from Acacia victoriae to inhibit chemically in-duced mouse skin carcinogenesis. The results suggest thatthese compounds could be potential suppressors of thedevelopment of human skin cancer and other epithelial ma-lignancies. Three new saponins, isolated from the fruits ofAcacia concinna Wall. (Leguminosae), were tested for cy-totoxic activity against human HT-1080 fibrosarcoma cells(Tezuka et al., 2000). All three saponins, kinmoonosides A,B and C exhibited significant cytotoxicity with ED50 valuesof 0.7, 0.91 and 2.83M, respectively. It is thought that theester moiety found at C-21 of the aglycone is not crucialfor the cytotoxicity but may rather intensify the activity.

Another novel triterpenoid saponin, pittoviridoside, wasisolated from Pittosporum viridiflorum Sims (Pittospo-raceae) using bioassay-guided fractionation with geneticallyengineered Saccharomyces cerevisiae mutant yeast strains(1138, 1140, 1353 and Sc-7) (Seo et al., 2002a). The com-pound was shown to have both weak cytotoxicity activityagainst A 2780 human ovarian cancer cell lines (IC5010.1g/ml) and weak activity against yeast strains.

Mixtures of saponins have also been shown to have cyto-toxic activities. Marquina et al. (2001) reported on a mixtureof monodesmoside saponins, which were not active as purecompounds, to be highly cytotoxic against P388 and coloncell lines (ED50 values of 2.3 and 3.6g/ml, respectively).

2.8. Antiviral activity

Saponins have also been reported to have antiviral activ-ities. Simes et al. (1999) tested two triterpenoid saponinsisolated from Brazilian and Chinese plants for their antiviralactivity. Both triterpenoid saponins exhibited antiviral activ-ity. The oleanane-type inhibited herpes simplex virus type1 DNA synthesis, while the ursane-type saponin inhibitedviral capsid protein synthesis of herpes simplex virus type 1.

Triterpenoid saponins from the Fabaceae family have beenreported to have anti-herpes virus activity (Kinjo et al.,2000). Anti-herpes simplex virus activity was found to be


structure related. Saponins having a glucosyl unit in the cen-tral sugar moiety seemed to show greater activity.

Triterpenoid saponins isolated from the leaves ofMaesa lanceolata Forssk. (Myrsinaceae) were tested forstructureactivity relationships against HSV-1 (for extra-cellular virucidal activity) and HIV viruses (Apers et al.,2001). It was concluded that a free 16-OH and acylationof the 22-OH appears to be essential for antiviral activity.These saponins, however, showed no anti-HIV activity andit was concluded that the cytotoxicity of the compoundswere more pronounced than a potential antiviral effect.

Arganine C, a saponin isolated from the fruits ofTieghemella heckelii Pierre ex A.Chev. (Sapotaceae) wasreported to have antiviral activity (Gosse et al., 2002). Thesaponin, strongly inhibited the entry of HIV into cells ina cell fusion assay, and showed no significant cytotoxicitytowards HeLa-CD4+ cells.

A mixture of tea-seed saponins from Camellia sinensisL. var sinensis (Ternstroemiaceae), were reported to inacti-vate human type A and B influenza viruses. However, thesesaponins were also toxic to the host cells and further studiesneed to be conducted (Hayashi et al., 1999).

The maesasaponin mixture isolated from Maesa lance-olata Forssk. (Myrsinaceae) was reported to have bothanti-herpes simplex virus type 1 (HSV-1) and poliovirus type1 activity (Sindambiwe et al., 1998). The saponin mixture re-duced the HSV-1 infectivity at a concentration of 100g/mland inactivated the Herpes simplex virus at 250g/ml.

Escin saponins isolated from the seeds of Aesculus chi-nensis Bunge (Hippocastanaceae) were tested for HIV-1protease inhibition (Yang et al., 1999). Eight saponins weretested, four of which were novel compounds. The escinsaponins inhibited 86.1 0.2% of the HIV-1 protease activ-ity at a concentration of 100M. A mixture of the saponinescin Ia and escin Ib showed 89.9 1.1% inhibitory activ-ity against HIV-1 protease at 100M. Escin Ia and escin Ibshowed inhibitory activity against HIV-1 protease with IC50values of 35M and 50M, respectively.

2.9. Other biological activities

The roots of Panax species (ginseng) have been found tocontain a series of tetracyclic triterpenoid saponins whichmake up the active ingredients. The saponin content is saidto vary between different Panax species (Nocerino et al.,2000). Ginseng saponins have been shown to have a widevariety of biological properties. The aphrodisiac and adap-togenic properties of Panax quinquefolium L. (Araliaceae)and Panax ginseng C.A.Meyer were reviewed by Nocerinoet al. (2000). It was concluded that when used appropri-ately, ginseng appears to be safe, but side effects are doc-umented. Attele et al. (1999) reviewed selected effects ofPanax species and their major active steroidal saponin com-ponents. The structure-function relationship and potentialtargets of action were discussed. The ability of ginseno-sides to independently target multireceptor systems at the

plasma membrane and activate intracellular steroid recep-tors is thought to explain their pharmacological effects.

Saponins from Ginseng Radix rubra (Panax ginsengC.A.Meyer, Araliaceae) were shown to have an effect onwound healing (Kanzaki et al., 1998). The study involvedexamining the effects of saponin on the extracellular matrixmetabolism, the activation and synthesis of TGF-1, andthe modification of TGF- receptor expressions in fibrob-lasts in order to clarify the contribution of the TGF- path-way to the mechanism of wound healing. It was concludedthat saponin stimulates the wound healing process throughchanges of the extracellular matrix metabolism and is ac-companied by modification of TGF- receptor expressionsin fibroblasts.

Huong et al. (1998a) investigated the antioxidant activityof Vietnamese ginseng (Panax vietnamensis Ha & Grushv.,Araliaceae) saponins. The results of the study showed thatVietnamese ginseng saponins exert protective action againstfree radical-induced tissue injury. However, the activity isattributed to the minor saponin components rather that themajor saponin components.

Korean red ginseng (Panax ginseng C.A.Meyer, Ar-aliaceae) saponins were also found to have an effect onethanol-induced amnesia (Lee et al., 2000). Jin et al.(1999) also worked on two Korean red ginseng saponins,protopanaxadiol and protopanaxatriol, and their effect indifferent ratios on scopolamine-induced learning abilityand spatial working memory in mice. The two saponinsimproved the scopolamine-induced learning impairmentat different dosages in the mice. However, neither of thesaponins showed a favorable effect on learning and mem-ory in normal mice. Different ratios of the two saponinswere shown to have different effects. A low protopanaxa-diol/protopanaxatriol ratio improved the spatial workingmemory of the mice. The reverse showed no improvementsuggesting that the protopanaxadiol/protopanaxatriol ratioof ginseng saponins may play an important role in thepharmacological effect of red ginseng. Une et al. (2001)investigated the effect of saponins on cognitive behaviourand anxiety in albino mice. The saponin mixture isolatedfrom Albizzia lebbeck Willd. (Leguminosae) significantlyimproved the retention ability of the normal and amnesicmice as compared to the respective controls.

Kim et al. (1998b) showed the effect of ginseng totalsaponin from the root of Panax ginseng C.A.Meyer (Arali-aceae) on morphine-induced hyperactivity and conditionedplace preference in mice. An intraperitioneal injection ofginseng total saponin prior to, and during the morphinetreatment in mice inhibited morphine-induced hyperactivityand conditioned place preference. A single dose of ginsengtotal saponin also inhibited apomorphin-induced climbingbehaviour which shows the antidopaminergic action of thesaponins at the postsynaptic dopamine receptor.

In another study by Kim et al. (1999) the administration ofginseng total saponin prior to and during the nicotine treat-ment in mice inhibited, not only nicotine-induced hyperac-


tivity and conditioned place preference, but also postsynap-tic dopamine receptor supersensitivity in nicotine-inducedconditioned place preference mice. The results suggest thatginseng total saponin may be useful for the prevention andtherapy of some of the adverse effects of nicotine.

A new oleanene-type saponin isolated from the flow-ers of Spartium junceum L. (Leguminosae) showed potentanti-ulcerogenic activity (Yesilada and Takaishi, 1999). Thesaponin named spartitrioside exerted a potent effect againstethanol-induced gastric lesions in rats. The activity was moreeffective than the reference compound, famotidine.

Saponins isolated from Polygala senega L. (Polygalaceae)had potential vaccine adjuvant activity, increasing specificimmune responses in mice immunized with ovalbumin andhens immunized with rotavirus (Estrada et al., 2000). Thesaponins increased specific antibody levels to the antigensin both the mice and hens. Saponins as potential adjuvantsfor orally-administered vaccines were reviewed by Sjlanderand Cox (1998). Special reference was made to the inductionof local and systemic immune responses and interactionswith the internal epithelium. Barr et al. (1998) also reviewedthe adjuvant activity of saponins. Saponins from Quillajasaponaria Molina (Rosaceae) and the relationships betweenadjuvant activity, toxicity and saponin structure were re-viewed. Oda et al. (2003) also examined the relationship be-tween adjuvant activity and saponin structure. The correla-tion between adjuvant activity and the amphipathic structureof soyasaponins was investigated. It is thought that the am-phipathic structure may indeed define the fundamental ad-juvanticity of saponins. In a brief overview by Kersten andCrommelin (2003) of iscoms which have built-in adjuvantsin the form of Quillaja saponin, recent research on the use ofbetter defined saponin adjuvants were discussed. Accordingto Johansson and Lvgren-Bengtsson (1999) iscoms that aremade up of different defined fractions of quillaja saponins,exhibit different immunomodulatory activities when testedfor serum antibody responses.

Triterpenoid saponins from the roots and flowerbuds of Panax notoginseng (Burk.) F.H.Chen (Arali-aceae) showed potent hepatoprotective effects on liverinjury induced by d-galactosamine and lipopolysaccha-ride (Yoshikawa et al., 2003). The major saponins iso-lated from the buds, ginsenosides-Rb3 and -Rc, showedstronger hepatoprotective activity than the major saponinsisolated from the roots, ginsenoside-Rb1 and -Rg1. Six-teen triterpenoid saponins from Panax vietnamensis Ha& Grushv. (Araliaceae) were also found to posses hepa-tocytoprotective effects on d-galactosamine/tumor necro-sis factor-alpha-induced cell death in primary culturedmouse hepatocytes (Tran et al., 2001a). From these re-sults it was concluded that the hepatocytoprotective ef-fect of Vietnamese ginseng is due to dammarane-typetriterpene saponins that have an ocotillol-type side chain.Tran et al. (2002) investigated the hepatoprotective ef-fect of majonoside R2 the major saponin constituent fromPanax vietnamensis. The saponin was tested in vivo on

d-galactosamine/lipopolysaccharide-induced hepatic apop-tosis and subsequent liver failure in mice. MajonosideR2 was found to protect primary cultured mouse hepato-cytes from cell death by inhibiting the induced apoptosis.Majonoside-R2, was also investigated for its effect onbehavioural and pathophysiological changes caused by psy-chological stress (Huong et al., 1998b). Majonoside-R2 at-tenuated communication box paradigm-induced psycholog-ical stress (CBP stress) and conditioned fear stress-inducedantinociception, and had a protective effect against CBPstress-induced gastric lesions. The saponin also restored thehypnotic activity of pentobarbital to levels similar to theunstressed controls. Saponins from different Panax specieshave been reported to demonstrate a number of actionson the central nervous system. Results from studies doneon saponins isolated from Panax japonicus C.A.Meyer(Araliacae), indicate that these saponins may be useful inthe treatment of neurodegenerative diseases (Zou et al.,2002a). Four new isolated yesanchinoside saponins togetherwith nine ginsenosides were tested. Ginsenosides Rb1 andRb4 and notoginsenosides R4 and Fa were shown to havesignificant neurite outgrowth activity in human neuroblas-toma SK-N-SH cells. These saponins were also found tosignificantly increase the total length of the neurites andthe number of varicosities per cell. Ginsenosides Rb1 andRb4 increased the total length of neurites by more thanthree times the control. Liao et al. (2002) also investigatedthe effect of saponins (ginseng total saponin) on neuro-logical disorders. The neuroprotective effects of ginsengtotal saponin and ginenosides Rb1 and Rg1 on spinal cordneurons were investigated. In vitro studies revealed gin-senosides Rb1 and Rg1, isolated from the roots of Panaxginseng C.A.Meyer (Araliaceae), as efficient neuroprotec-tive agents. The saponins protected the spinal neurons fromexcitotoxicity induced by glutamate and kainic acid, aswell as oxidative stress induced by hydrogen peroxide. Theeffects were shown to be dose dependent, with the optimaldose of 2040M to be most effective.

In a study by Herlt et al. (2002), two major saponins, 3-O-{[-d-galactopyranosyl-(1 3)--d-glucopyranosyl(1 2)]--d-glucuronopyranosyloxy}-22-O-(2-methylbutyroyl-oxy)-15,16,28-trihydroxy-(3,15,16,22)-olean-12-eneand 3-O-{[-d-galactopyranosyl(1 3)--d-glucopyra-nosyl(1 2)]--d-glucuronopyranosyloxy}-22-O-(2(E)-methyl-2-butenyloyloxy)-15,16,28-trihydroxy-(3,15,16,22)-olean-12-ene, were isolated from the seeds of Bar-ringtonia asiatica Kurz (Lecythidaceae) and tested forantifeedant properties towards Epilachna larvae. Thesaponins were tested at concentrations of 1000, 500, 100and 50g/ml on Solanum nigrum leaves. The resultsshowed the saponin contaning tiglate to have consider-ably higher antifeedant activity than the saponin contain-ing 2-methylbutyrate. At a concentration of 100g/ml,the tiglate-containing saponin had 39% antifeedant activ-ity and the 2-methylbutyrate-containing saponin had 0%activity.


Three novel ginseng saponin metabolites formed byintestinal bacteria were evaluated for their antigenotoxicproperties (Lee et al., 1998). The compounds inhibitedbenzopyrene-induced mutagenicity in a dose-dependentmanner. It was suggested that the results indicate thatthese ginseng saponin metabolites could have potentialas chemopreventive agents. Scarpato et al. (1998) inves-tigated the effects of isolated saponins from Bupleurumfruticosum L. (Apiaceae) on the clastogenicity and cytotox-icity of the anticancer drugs mitomycin C and bleomycin.One of the saponins showed a dose-dependent mitomycinC-induced mutagenesis inhibition and a co-genotoxic ef-fect on bleomycin-treated cultures. Soybean (Glycine maxMerrill., Leguminosae) extracts have been shown to repressinduced genomic DNA damage, cell clastogenicity andpoint mutation in cultured mammalian cells. Berhow et al.(2000) showed that a mixture of soyasaponins repressed2-acetoxyacetylaminofluorene (2AAAF)-induced DNAdamage in Chinese hamster ovary cells. Soyasapogenol Baglycone showed significant antigenotoxic activity against2AAAF. These results are the first to demonstrate the an-timutagenic activity of soybean saponins in mammaliancells. Yoshiki et al. (1998) reviewed the relationship be-tween the chemical structure and biological activities oftriterpenoid saponins isolated from Glycine max Merrill.(Leguminosae).

Saponins isolated from the roots of Zygophyllum gaetu-lum Emb. & Maire (Zygophyllaceae) were tested for theireffects on electrically-stimulated guinea-pig ileum (Aquinoet al., 2001). The results showed that the saponin zygophy-loside N significantly reduced the electrically-induced con-tractions. The antispasmodic activity shown by this saponinwas dose-dependent.

Table 1A list of plant species from which saponins have been isolated in recent years (19982003)Family Species Saponin type Reference

Agavaceae Agave americana L. Steroidal Yokosuka et al., 2000aAgave attenuataSalm-Dyck

Steroidal da Silva et al., 2002

Agave decipiens Baker Steroidal Abdel-Gawad et al., 1999Cordyline stricta (Sims)Endl.

Steroidal Mimaki et al., 1998d

Furcraea foetida (L.) Haw. Steroidal Itabashi et al., 1999Yucca filamentosa L. Steroidal Plock et al., 2001Yucca schidigera Roezl. exOrtgies

Steroidal Miyakoshi et al., 2000

Oleszek et al., 2001

Alliaceae Allium chinense G.Don Steroidal Baba et al., 2000Allium karataviense Regel Steroidal Mimaki et al., 1999bAllium nutans L. Steroidal Akhov et al., 1999Allium porrum L. Steroidal Carotenuto et al., 1999

Fattorusso et al., 2000Allium triquetrum L. Steroidal Corea et al., 2003Allium tuberosum Rottl. exSpreng.

Steroidal Sang et al., 1999a, 1999b, 2001a, 2001b

Zou et al., 2001

In a study by Parab and Mengi (2002) saponins ex-tracted from Acorus calamus L. (Araceae) were tested forhyperlipidemic activity. Treatments of hyperlipidemic ratswith saponins (10 mg/kg) significantly decreased the serumcholesterol and triglyceride levels. However, neither of thelipoprotein levels were brought down to baseline values,but it was still concluded that the saponins contribute tothe hypolipidemic activity of A. calamus. Saponin frac-tions from Allium species have been shown to decrease theplasma total cholesterol levels (Matsuura, 2001). The ac-tive fractions contained steroid saponins which are thoughtto be responsible for the cholesterol lowering effects ofgarlic. In a minireview of natural products and their biolog-ical activities, saponins were listed under compounds withhypocholesterolemic activity (Wang and Ng, 1999).

3. Distribution of saponins

Saponins are found in a wide variety of foods includingasparagus, beans, blackberries, peas, potatoes, sugar beetand tea (Dini et al., 2001a). They occur in many differentplant families, as evidenced by the isolation of saponinsfrom phytochemical studies of many plant species overthe years. Table 1 provides a list of species from whichsaponins have been isolated in the last 5 years (19982003).Although this list is not exhaustive, it does give a good indi-cation of the plant species and families which have formedthe focus of research in saponin chemistry in recent years.Many of these species have been chosen for phytochemicalresearch based on ethnobotanical use. Of the roughly 200species listed, 40% of the species were investigated basedtheir traditional usage. Two triterpenoid saponins, eliciting


Table 1 (Continued )Family Species Saponin type Reference

Amaranthaceae Achyranthes aspera L. Triterpenoid Kunert et al., 2000Michl et al., 2000

Achyranthes bidentataBlume

Triterpenoid Mitaine-Offer et al., 2001a, 2001b

Alternanthera repens (L.)Link

Triterpenoid Sanoko et al., 1999

Amaranthus caudatus L. Triterpenoid Rastrelli et al., 1998Amaranthus cruentus L. Triterpenoid Junkuszew et al., 1998

Oleszek et al., 1999

Apiaceae (Umbelliferae) Bupleurum falcatum L. Triterpenoid Ahn et al., 1998Bupleurum fruticescensL.

Triterpenoid Just et al., 1998

Bupleurum rigidum L. Triterpenoid Sanchez-Contreras et al., 1998, 2000Bupleurum rotundifoliumL.

Triterpenoid Navarro et al., 2001

Fujioka et al., 2003Bupleurumscorzonerifolium Willd.

Triterpenoid Li et al., 1999a

Centella asiatica (L.)Urb.

Triterpenoid Matsuda et al., 2001

Aquifoliaceae Ilex amara (Vell.) Loes. Triterpenoid de Andrade et al., 2002Ilex kudincha C.J.Tseng Triterpenoid Nishimura et al., 1999Ilex latifolia Thunb. Triterpenoid Huang et al., 2001a, 2001b

Ouyang et al., 1998

Araliaceae Acanthopanaxnipponicus Makino

Triterpenoid Miyakoshi et al., 1999

Aralia dasyphylla Miq. Triterpenoid Xiao et al., 1999Aralia elata (Miq.) Seem. Triterpenoid Song et al., 2000, 2001Cussonia bancoensisAubrev. & Pellegr.

Triterpenoid Tapondjou et al., 2003

Cussonia racemosa Baker Triterpenoid Harinantenaina et al., 2002Hedera colchica K.Koch Triterpenoid Delmas et al., 2000

Mshvildadze et al., 2000, 2001Barthomeuf et al., 2002

Hedera helix L. Triterpenoid Delmas et al., 2000Bedir et al., 2000

Kalopanax pictus Nakai Triterpenoid Park et al., 2001Li et al., 2002Choi et al., 2002

Meryta lanceolata Forst. Triterpenoid Melek et al., 2003Panax ginseng C.A.Mey. Triterpenoid Dou et al., 2001Panax japonicusC.A.Mey.

Triterpenoid Zou et al., 2002a, 2002b

Panax notoginseng(Burk.) F.H.Chen

Triterpenoid Ma et al., 1999

Yoshikawa et al., 2001, 2003Panax pseudo-ginsengWall.

Triterpenoid Tanaka et al., 2000

Panax vietnamensis Ha& Grushv.

Triterpenoid Huong et al., 1998b

Tran et al., 2001a, 2002Polyscias fruticosa (L.)Harms [= Panaxfruticosum L.;Nothopanax fruticosumMiq.]

Triterpenoid Huan et al., 1998

Schefflera leucanthaR.Vig.

Saponin mixture Witthawaskul et al., 2003

Trevesia palmata (Roxb.ex Lindl.) Vis.

Triterpenoid De Tommasi et al., 2000

Tupidanthus calyptratusHook.f. & Thoms.

Triterpenoid Cioffi et al., 2001



Asclepiadaceae Gymnema sylvestre R.Br. Triterpenoid Ye et al., 2000, 2001

Asparagaceae Asparagus africanusLam.

Steroidal Debella et al., 1999

Asparagus dumosusBaker

Steroidal Ahmad et al., 1998

Asteraceae Aspilia montevidensis(Spreng.) Kuntze

Steroidal Bellini et al., 1999

Aster ageratoides Turcz.var. ovatus Nakai

Triterpenoid Sakai et al., 1999

Celmisia spectablilisHook.f.

Triterpenoid Ueckert et al., 1998

Conyza blinii Levl. Triterpenoid Su et al., 2001, 2003Viguiera decurrensA.Gray

Triterpenoid Marquina et al., 2001

Balanitaceae Balanites aegyptiaca Del. Steroidal Kamel, 1998

Berberidaceae Bongardia chrysogonum(L.) Boiss.

Triterpenoid Atta-ur-Rahman et al., 2000

Caulophyllumthalictroides (L.) Michx.

Triterpenoid Jhoo et al., 2001

Buddlejaceae Buddleja scordioidesHBK.

Triterpenoid Avila and Romo de Vivar, 2002

Cactaceae Isolatocereus dumortieriBr. & R. [= Isolatocereusdumortieri Backeb.]

Triterpenoid Kinoshita et al., 2000

Campanulaceae Platycodon grandiflorumA.DC.

Triterpenoid Nikaido et al., 1999

Caprifoliaceae Lonicera bournei Hemsl. Triterpenoid Xiang et al., 2000Lonicera japonica Thunb. Triterpenoid Kwak et al., 2003

Caryophyllaceae Acanthophyllumsquarrosum Boiss.[= Acanthophyllumpungens (Bunge) Boiss.var. squarrosum Golenk.]

Triterpenoid Gaidi et al., 2000b, 2001b

Arenaria filicaulis Boiss.[= Gypsophila filicaulis(Boiss.) Borm]

Triterpenoid Elgamal et al., 1998

Soliman et al., 1999, 2001Arenaria juncea M.Bieb. Triterpenoid Gaidi et al., 2001aGypsophila bermejoiG.Lopez

Triterpenoid Acebes et al., 1998a, 1998b

Polycarpon succulentumJ.Gay

Triterpenoid Meselhy, 1998

Saponaria officinalis L. Triterpenoid Jia et al., 1998b, 1999Koike et al., 1999a

Silene cucubalus Wibel Triterpenoid Larhsini et al., 2003Silene fortunei Vis. Triterpenoid Lacaille-Dubois et al., 1999a, 1999b

Gaidi et al., 2002Silene vulgaris (Moench)Garcke [= Silene inflataSm.]

Triterpenoid Glensk et al., 1999

Spergularia ramosaCambess.


Vaccaria segetalis(Neck.) Garcke[= Vaccaria pyramidataMedik.]

Triterpenoid Jia et al., 1998a

Koike et al., 1998Yun et al., 1998Ma et al., 2001



Chenopodiaceae Beta vulgaris L. Triterpenoid Murakami et al., 1999aChenopodium album L. Triterpenoid Lavaud et al., 2000Chenopodium ficifoliumSm.

Triterpenoid Gohar et al., 2002

Chenopodium quinoaWilld.

Triterpenoid Dini et al., 2001a, 2001b

Woldemichael and Wink, 2001Dini et al., 2002Zhu et al., 2002

Combretaceae Pteleopsis hylodendronMildbr.

Triterpenoid Ngounou et al., 1999

Cucurbitaceae Cucurbita foetidissimaH.B. & K. [= Cucurbitaperrenis A.Gray; Cucumisperrenis E.James]

Triterpenoid Gaidi et al., 2000a

Cyclanthera pedataSchrad.


Momordica charantia L. Triterpenoid Murakami et al., 2001a

Diapensiaceae Berneuxia thibeticaDecne.

Triterpenoid Wang et al., 1998

Dioscoreaceae Dioscorea panthaicaPrain & Burkill

Steroidal Dong et al., 2001a, 2001b

DioscoreapseudojaponicaYamamoto

Steroidal Yang et al., 2003

Dipsacaceae Scabiosa rotata M.Bieb. Triterpenoid Baykal et al., 1998

Dracaenaceae Dracaena angustifoliaRoxb.

Steroidal Tran et al., 2001b

Dracaena concinnaKunth

Steroidal Mimaki et al., 1998e

Dracaena draco L. Steroidal Mimaki et al., 1999cGonzalez et al., 2003

Dracaena surculosaLindl.

Steroidal Yokosuka et al., 2000b, 2002a

Sansevieria cylindricaBoj.

Steroidal Antunes et al., 2003

Eupteleaceae Euptelea polyandra Sieb.& Zucc.

Triterpenoid Yoshikawa et al., 2000b

Murakami et al., 2001b

Hippocastanaceae Aesculus chinensis Bunge Triterpenoid Yang et al., 1999Zhang et al., 1999aZhao et al., 2001

Lamiaceae Becium grandiflorum(Lam.) Pichi-Serm.

Triterpenoid Burger et al., 1998

var. obovatum (E.Mey. exBenth) Sebald

Lardizabalaceae Holboellia fargesi Reaub. Triterpenoid Fu et al., 2001Lecythidaceae Barringtonia asiatica

KurzTriterpenoid Herlt et al., 2002

Foetidia africana Verdc. Triterpenoid Crublet et al., 2002Petersianthusmacrocarpus (P.Beauv.)Liben

Triterpenoid Olugbade et al., 2000

Leguminosae Acacia concinna Wall. Triterpenoid Tezuka et al., 2000Acacia tenuifolia (L.)Willd.

Triterpenoid Seo et al., 2002b

Acacia victoriae Benth. Triterpenoid Hanausek et al., 2001



Mujoo et al., 2001Jayatilake et al., 2003

Albizia gummifera C.A.Sm. Triterpenoid Debella et al., 2000Albizia julibrissin Durazz. Triterpenoid Zou et al., 2000Albizia lebbeck Willd. Saponin mixture Une et al., 2001Albizia myriophylla Benth. Triterpenoid Yoshikawa et al., 2002Albizia procera Benth. Triterpenoid Yoshikawa et al., 1998Albizia subdimidiata(Splitg.)

Triterpenoid Abdel-Kader et al., 2001

Barneby & J.W.GrimesAstragalus kahiricus DC. Triterpenoid Verotta et al., 2002Astragalus trigonus DC. Triterpenoid Shaker et al., 2001Baptisia australis (L.) R.Br. Triterpenoid Udayama et al., 1998Gleditsia sinensis Lam. Triterpenoid Zhang et al., 1999b, 1999c, 1999dGliricidia sepium (Jacq.)Walp.

Triterpenoid Kojima et al., 1998

Gliricidia sepium (Jacq.)Steud.

Rastrelli et al., 1999

Lathyrus japonicus Willd.[= Lathyrus maritimusBigel.]

Triterpenoid Kang et al., 1998

Lupinus oreophilus Phil. Triterpenoid Woldemichael et al., 2003Medicago sativa L. Triterpenoid Bialy et al., 1999Spartium junceum L. Triterpenoid Yesilada and Takaishi, 1999Swartzia schomburgkiiBenth.

Triterpenoid Abdel-Kader et al., 2000

var. schomburgkiiTrifolium spp. Triterpenoid Oleszek and Stochmal, 2002Trifolium resupinatum L. Triterpenoid Simonet et al., 1999Trigonellafoenum-graecum L.

Steroidal Murakami et al., 2000a

Vigna angularis (Willd.)Ohwi & H.Ohashi

Triterpenoid Iida et al., 1999

Liliaceae Camassia leichtlinii (Bak.)S.Wats.

Steroidal Kuroda et al., 2001

Chlorophytum malayenseRidl.

Steroidal Qiu et al., 2000

Hemerocallis fulva L. Steroidal Konishi et al., 2001var. kwansoHosta sieboldii (Paxton)I.Ingram

Steroidal Mimaki et al., 1998c

Lilium candidum L. Steroidal Haladova et al., 1998Mimaki et al., 1999e

Polygonatumzanlanscianense Pamp.

Steroidal Wang et al., 2001

Ruscus aculeatus L. Steroidal Mimaki et al., 1998a, 1998b, 1999dRuscus colchicus Yeo Steroidal de Combarieu et al., 2002Ruscus hypoglossum L. Steroidal de Combarieu et al., 2002Tupistra wattii Hook.f. Steroidal Shen et al., 2003

Lythraceae Lafoensia glyptocarpaKoehne

Triterpenoid de Carvalho et al., 1999

Menispermaceae Diploclisia glaucescens(Bl.) Diels [= Cocculusmacrocarpus Wight &Arn.]

Triterpenoid Jayasinghe et al., 2003

Molluginaceae Glinus lotoides L. var.dictamnoides [= Glinusdictamnoides Burm.f.;Mollugo glinus A.Rich]

Triterpenoid Hamed and El-Emary, 1999

Glinus oppositifolius L. Triterpenoid Traore et al., 2000Mollugo spergula L. Triterpenoid Sahu et al., 2001



Myrsinaceae Ardisia crenata Roxb. Triterpenoid Koike et al., 1999bArdisia mamillata Hance Triterpenoid Huang et al., 2000a, 2000bMaesa japonica (Thunb.)Mor. & Zoll.

Triterpenoid Koike et al., 1999c

Maesa lanceolata Forssk. Triterpenoid Sindambiwe et al., 1998var. golungensis Welw. Apers et al., 1999, 2001Maesa laxiflora Pitard Triterpenoid Jiang et al., 1999Maesa tenera Mez Triterpenoid Koike et al., 2001

Passifloraceae Passiflora edulis Sims Triterpenoid Yoshikawa et al., 2000aPhytolaccaceae Phytolacca dioica L. Triterpenoid Soliman et al., 2001

Phytolacca dodecandraLHer.

Saponin mixture Mlgaard et al., 2000

Phytolacca icosandra L. Triterpenoid Treyvaud et al., 2000Phytolacca tetrameraHauman

Triterpenoid Escalante et al., 2002

Pittosporaceae Pittosporum viridiflorumSims

Triterpenoid Seo et al., 2002a

Polygalaceae Carpolobia alba G.Don. Triterpenoid Mitaine-Offer et al., 2002Carpolobia lutea G.Don. Triterpenoid Mitaine-Offer et al., 2002Polygala amarella Crantz Triterpenoid Desbene et al., 1999Polygala senega L. Triterpenoid Estrada et al., 2000Securidacainappendiculata Hassk.

Triterpenoid Yui et al., 2001

Primulaceae Cyclamen coum mill. Triterpenoid Yayli et al., 1998

Ranunculaceae Cimicifuga foetida L. Triterpenoid Zhu et al., 2001Clematis tangutica(Maxim.) Korsh.

Triterpenoid Zhong et al., 2001

Clematis tibetana Kuntze Triterpenoid Kawata et al., 2001Eranthis cilicica Schott& Kotschy

Triterpenoid Watanabe et al., 2003

Nigella sativa L. Triterpenoid Kumara and Huat, 2001Pulsatilla chinensis(Bunge) Regel

Triterpenoid Mimaki et al., 1999a

Pulsatilla patens Millvar. multifida (Pritz.)S.H.Li & Y.H.Huang

Triterpenoid Ye et al., 1999

Thalictrum minus L. Triterpenoid Gromova et al., 1998

Rhamnaceae Colubrina retusa L. Triterpenoid ElSohly et al., 1999Li et al., 1999b

Zizyphus joazeiro Mart. Triterpenoid Schhly and Heilmann, 2000Zizyphus jujuba Mill.var. spinosa Hu.

Triterpenoid Matsuda et al., 1999

Rosaceae Quillaja saponariaMolina

Triterpenoid Guo et al., 1998, 2000

Guo and Kenne, 2000a, 2000bMarciani et al., 2001

Rubus pungens Camb.var. oldhamii Maxim.

Triterpenoid Wang et al., 2000

Rubiaceae Galium rivale (Sibth. &Sm.) Griseb.

Triterpenoid de Rosa et al., 2000a, 2000b

Hedyotis nudicaulisWight & Arn.

Triterpenoid Konishi et al., 1998

Isertia pittieri (Standl.)Standl.

Triterpenoid Um et al., 2001

Randia formosaK.Schum.

Triterpenoid Sahpaz et al., 2000

Rudgea viburnoides(Cham.) Benth.

Triterpenoid Young et al., 1998



Sapindaceae Elattostachys apetala(Labill.) Radlk.[= Elattostachys falcata(A. Gray) Radlk.]

Triterpenoid Lavaud et al., 2001

Filicium decipiensThwaites

Triterpenoid Lavaud et al., 1998

Harpulliaaustro-caledonica Boull.

Triterpenoid Voutquenne et al., 2002

Harpullia cupanioidesRoxb.


Harpulia ramiflora Radlk. Triterpenoid Dizes et al., 1998Koelreuteria paniculataLaxm.

Triterpenoid Soliman et al., 2001

Pometia ridleyi Kingemend. Radlk.


Sapindus emarginatus Vahl. Triterpenoid Kanchanapoom et al., 2001Sapindus mukorossi Gaertn. Triterpenoid Huang et al., 2003

Sapotaceae Argania spinosa (L.) Skeels Triterpenoid Alaoui et al., 2002Gambeya boukokoensisAubrev. & Pellegr.

Triterpenoid Wandji et al., 2003

Madhuca longifolia (L.)Macbride [= Bassialongifolia L.]

Triterpenoid Yoshikawa et al., 2000c

Tieghemella heckelii Pierreex A.Chev.

Triterpenoid Gosse et al., 2002

Scrophulariaceae Bacopa monniera Wettst. Triterpenoid Pawar et al., 2001

Solanaceae Capsicum annuum L. var.acuminatum Fingerh.

Steroidal Iorizzi et al., 2002

Capsicum frutescens L. Steroidal de Lucca et al., 2002Cestrum nocturnum L. Steroidal Mimaki et al., 2001aCestrum sendtnerianumMart. Ex Sendt.

Steroidal Haraguchi et al., 1999, 2000

Lycopersicon esculentumMill.

Steroidal Fujiwara et al., 2003

Solanum chrysotrichumSchldh.

Steroidal Alvarez et al., 2001

Zamilpa et al., 2002Solanum khasianumC.B.Clarke

Steroidal Putalun et al., 1999

Styracaceae Styrax officinalis L. Triterpenoid Yayla et al., 2002Taccaceae Tacca chantrieri Andre Steroidal Yokosuka et al., 2002b

Ternstroemiaceae Triterpenoid Murakami et al., 1999b, 2000bCamellia sinensis L. var.assamica Pierre

Lu et al., 2000

Ternstroemia japonicaThunb.

Triterpenoid Shin et al., 2003

Tiliaceae Corchorus depressus L. Triterpenoid Ahmad et al., 2000

Verbenaceae Duranta repens L. Triterpenoid Hiradate et al., 1999

Zygophyllaceae Fagonia cretica L. Triterpenoid Khalik et al., 2000Fagonia indica Burm.f. Triterpenoid Shaker et al., 1999Tribulus terrestris L. Steroidal Xu et al., 2000

Cai et al., 2001Kostova et al., 2002de Combarieu et al., 2003

Zygophyllum decumbensDel.

Triterpenoid Pllmann et al., 1998

Zygophyllum gaetulumEmb. & Maire

Triterpenoid Safir and Fkih-Tetouani, 1998

Aquino et al., 2001


the typical response in cancer cells, were isolated from theroot bark of Becium grandiflorum (Lam.) Pichi-Serm. var.obovatum (E.Mey. ex Benth) Sebald (Lamiaceae) due to thetraditional use of the plant (along with four others) for thetreatment of breast and buccal cancer (Burger et al., 1998).A further 10% of the species listed were selected based onprevious ethnobotanical studies on related species eitherof the same genus or family. Allium nutans L. (Alliaceae),a wild species of onion, was investigated because of themany reports on the steroidal saponins from Allium species(Akhov et al., 1999). This approach to drug discovery hasreceived renewed interest in recent years, and potentiallyincreases the chances for the discovery of novel therapeuticagents (Fabricant and Farnsworth, 2001).

As mentioned earlier, steroidal saponins are almost ex-clusively found in the monocotyledonous angiosperms. Thistrend is confirmed by the presence of steroidal saponins inthe monocotyledonous families of the Agavaceae, Alliaceae,Asparagaceae, Dioscoreaceae, Dracaenaceae, Liliaceae andTaccaceae. Interestingly, although the family Solanaceae isdicotyledonous, all the species studied contained steroidalsaponins. Other exceptions include the presence of steroidalsaponins in Aspilia montevidensis (Asteraceae), Balan-ites aegyptiaca (Balanitaceae), Trigonella foenum-graecum(Leguminosae) and Tribulus terrestris (Zygophyllaceae).

Eighteen species of the family Araliaceae have been ex-tensively investigated, as seen in Table 1, five of which arefrom the genus Panax. Species of Panax (ginseng) have beenknown to contain saponins for centuries, however, recentstudies on ginseng saponins have investigated their biologi-cal activities (Huong et al., 1998b; Kim et al., 1998b; Kimand Kim, 1999; Tran et al., 2001a, 2002; Liao et al., 2002;Zou et al., 2002a; Yoshikawa et al., 2003). The Leguminosaehave also been extensively investigated for saponins, in par-ticular, species of Acacia, Albizia and Astragalus. Table 1lists 23 species of the Leguminosae from which saponinshave been isolated.

4. Conclusion

Saponins are a diverse family of secondary metabolitesproduced by many plants species. Many plants used in tra-ditional medicine worldwide contain saponins, which canoften account for there therapeutic action. It is believed thatthe natural role of these compounds in plants is to protectagainst attack by potential pathogens, which would accountfor their antimicrobial activity (Osbourn, 2003). Althoughsaponins are extremely toxic to cold-blooded animals, theiroral toxicity to mammals is low (Dini et al., 2001a, 2001b).Due to their toxicity to various organisms, saponins canbe utilised for their insecticidal, antibiotic, fungicidal, andpharmacological properties. The wide chemical diversity ofboth triterpenoid and steroidal saponins has resulted in re-newed interest and investigations of these compounds in re-cent years, particularly as potential chemotherapeutic agents.

This review, and the list of species presented in Table 1, pro-vides a summary of saponin research in the last 5 years. Ithighlights important areas of research in this field, and theopportunity which exists for further research on the phy-tochemistry and biological activity of this group of com-pounds. Balandrin et al. (1993) estimate that at least 85%of the worlds estimated 250 000 species of higher plantshave not been adequately surveyed for potentially useful bi-ological activity. As a result, the chances of discovering newplant constituents, including novel saponins, which may bebiologically active are promising.

Acknowledgements

The National Research Foundation (NRF) and the Uni-versity of KwaZulu-Natal are gratefully acknowledged forproviding financial assistance.

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De Tommasi, N., Autore, G., Bellino, A., Pinto, A., Pizza, C., Sorrentino,R., Venturella, P., 2000. Antiproliferative triterpene saponins fromTrevesia palmata. Journal of Natural Products 63, 308314.

Debella, A., Haslinger, E., Kunert, O., Michl, G., Abebe, D., 1999.Steroidal saponins from Asparagus africanus. Phytochemistry 51,10691075.

Debella, A., Haslinger, E., Schmid, M.G., Bucar, F., Michl, G., Abebe,D., Kunert, O., 2000. Tritermpenoid saponins and sapogenin lactonesfrom Albizia gummifera. Phytochemistry 53, 885892.

Delmas, F., Di Giorgio, C., Elias, R., Gasquet, M., Azas, Mshvildadze,V., Dekanosidze, G., Kemertelidze, E., Timon-David, P., 2000. An-tileishmanial activity of three saponins isolated from ivy, -hederin,-hederin and hederacolchiside A1, as compared to their action onmammalian cells cultured in vitro. Planta Medica 66, 343347.

Desbne, S., Hanquet, B., Shoyama, Y., Wagner, H., Lacaille-Dubois,M.-A., 1999. Biologically active triterpene saponins from callus tissueof Polygala amarella. Journal of Natural Products 62, 923926.

Dini, I., Schettino, O., Simioli, T., Dini, A., 2001a. Studies on the con-stituents of Chenopodium quinoa seeds: isolation and characterizationof new triterpene saponins. Journal of Agricultural and Food Chem-istry 49, 741746.

Dini, I., Tenore, G.C., Schettino, O., Dini, A., 2001b. New oleananesaponins in Chenopodium quinoa. Journal of Agricultural and FoodChemistry 49, 39763981.

Dini, I., Tenore, G.C., Dini, A., 2002. Oleanane saponins in kancolla,a sweet variety of Chenopodium quinoa. Journal of Natural Products65, 10231026.


Dizes, C., Gerald, F., Lavaud, C., Elias, R., Faure, R., Massiot, G., Bal-ansard, G., 1998. Harpuloside A triterpenoid saponins from Harpulliaramiflora. Phytochemistry 48, 12291232.

Dong, M., Feng, X.-Z., Wang, B.-X., Wu, L.-J., Ikejima, T., 2001a. Twonovel furostanol saponins from the rhizomes of Dioscorea panthaicaPrain et Burkill and their cytotoxic activity. Tetrahedron 57, 501506.

Dong, M., Feng, X.-Z., Wu, L.-J., Wang, B.-X., Ikejima, T., 2001b. Twonew steroidal saponins from the rhizomes of Dioscorea panthaica andtheir cytotoxic activity. Planta Medica 67, 853857.

Dou, D.-Q., Chen, Y.-J., Liang, L.-H., Pang, F.-G., Shimizu, N., Takeda,T., 2001. Six new dammarane-type triterpene saponins from the leavesof Panax ginseng. Chemical and Pharmaceutical Bulletin 49, 442446.

Elgamal, M.H.A., Soliman, H.S.M., Elmunajjed, D.T., Tth, G., Simon,A., Duddeck, H., 1998. Two triterpene saponins from Arenaria fili-caulis. Phytochemistry 49, 189193.

ElSohly, H.N., Danner, S., Li, X.-C., Nimrod, A.C., Clark, A.M., 1999.New antimycobacterial saponin from Colubrina retusa. Journal ofNatural Products 62, 13411342.

Escalante, A.M., Santecchia, C.B., Lpez, S.N., Gattuso, M.A., Ravelo,A.G., Monache, F.D., Sierra, M.G., Zacchino, S.A., 2002. Isolation ofantifungal saponins from Phytolacca tetramera, an Argentinean speciesin critic risk. Journal of Ethnopharmacology 82, 2934.

Estrada, A., Katselis, G.S., Laarveld, B., Barl, B., 2000. Isolation andevaluation of immunological adjuvant activities of saponins from Poly-gala senega L. Comparative Immunology. Microbiology and InfectiousDiseases 23, 2743.

Fabricant, D.S., Farnsworth, N.R., 2001. The value of plants used in tradi-tional medicine for drug discovery. Environmental Health Perspectives109, 6975.

Fattorusso, E., Lanzotti, V., Taglialatela-Scafati, O., Di Rosa, M., Ianaro,A., 2000. Cytotoxic saponins from bulbs of Allium porrum L. Journalof Agricultural and Food Chemistry 48, 34553

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Plant Saponins