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Cancer is a disease in which body cells become abnormal and divide without

control (Nagarani et al., 2011). Multiplication of the cells is a normal physiological

process that occurs in almost all the tissues (Thompson, 1995). During cells proliferation,

the cell-cycle progression is regulated by positive and negative signals to ensure the

integrity of organs and tissues. Apoptosis, also called programmed cell death and mitosis,

share some common morphological features such as cell shrinkage, chromatin

condensation and membrane blebbing. Thus, the balance between apoptosis and

proliferation must be strictly maintained to sustain tissue homeostasis (Alenzi, 2004). The

inactivation of programmed cell death has profound effects not only on the development

but also on the overall integrity of multicellular organisms. Beside developmental

abnormalities, it may lead to tumorigenesis, autoimmunity, and other serious health

problems. Deregulated apoptosis may also be the leading cause of cancer therapy chemo-

resistance (Ghavami et al., 2009).

In the continuing search for agents that may treat or improve the suffering due to

cancer, natural products have provided an endless supply of active compounds that are

increasingly being exploited (Deorukhkar et al., 2007). Effective, curative chemotherapy

has been a goal of modern cancer medicine for half a century (Weiner and Lotze, 2012). It

involves the systemic administration of anticancer drugs that travel throughout the body

via circulatory system. The ancient civilizations of the Chinese, Indians and North

Africans provide written evidence for the use of natural sources for curing various

diseases. The earliest known written document is a 4000 year old Sumerian clay tablet that

records remedies for various illnesses. India too has one of the richest plants medical

traditions in the world. Herbal drugs constitute a major share of all the officially

recognised systems of health in India viz. Ayurveda, Yoga, Unani, Siddha, Homeopathy

and Naturopathy, except Allopathy. The ancient texts like Rig Veda (4500-1600 BC) and

Atharva Veda mention the use of several plants as medicine. The books on Ayurvedic

medicines such as Charaka Samhita and Susruta Samhita refer to the use of more than 700

herbs and there are approximately 25,000 effective plant-based formulations, used in folk

medicine and known to rural communities in India (Jain, 1968). There are over 1.5 million

practitioners of traditional medicinal system using medicinal plants in preventive,

promotional and curative applications. It is estimated that there are over 7800 medicinal

drug-manufacturing units in India, which consume about 2000 tonnes of herbs annually.

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For over 40 years, natural products have served us well in combating cancer

(Demain and Vaishnav, 2011). Plants have a long history of use in the treatment of cancer

(Kaur et al., 2011). According to Shankar et al. (2012), plants derived agents are of

considerable interest among oncologists. In the field of oncology, significant numbers of

commercialized drugs have been obtained from natural sources, either by structural

modification or by semisynthetic preparation. The search for improved cytotoxic agents is

important in the discovery of modern anti-cancer drugs (Nobili et al., 2009, Bagya et al.,

2011). Between the years 1981-2006, about a hundred anticancer agents have been

developed, of which, twenty five are natural product derivatives, eighteen are natural

product mimics, eleven candidates are derived from a natural product pharmacophore, and

nine are pure natural products (Newmann and Cragg, 2007). Thus, natural sources make a

very significant contribution to the health care system. Drug discovery involves a

multidisciplinary research effort to identify active molecules with desirable biological

effects. Major steps in preclinical drug discovery include synthesis, identification,

screening and assaying of chemical compounds etc. (Balachandran and Govindarajan,

2007).

A systematic drug screening began in 1955 at the National Cancer Institute (NCI)

with the establishment of the Cancer Chemotherapy National Service Center screening

programme (Zubrod, 1972). Throughout 1960s and 1970s, most screening was performed

in vivo using mouse L1210 and P388 leukemias. Although reproducible, stable and

relatively inexpensive, the use of rapidly dividing haematological mouse tumours

introduced bias in the screens in favour of agents with activity against tumors with high

growth fractions (Takimoto, 2003). The inadequacy of these screening models for

selecting agents active against solid tumors was implicated, at least in part, for the

relatively slow progress in advancing treatments for common tumors. In an attempt to find

drugs active against solid tumours, the NCI in 1976, adopted human tumour xenografts

into its in vivo screening programme (Kelland, 2004). The first three human tumour

xenografts included colon (CX-1), breast (MX-1) and lung (LX-1) tumors, but overall

more than 300 xenografts have been established representing most main tumour types. In a

parallel effort, the NCI introduced, in 1989, what was initially called ‘disease-oriented’

screening. This new approach used a rationally designed screening panel containing 60

cell lines derived from seven different human cancer types, including colon, brain, lung,

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melanoma, ovarian, renal and leukemia. Subsequently, breast and prostate cell lines were

added (Boyd, 1997). The use of the human cell line screening approach was increased by

Kenneth Paull and colleagues, who established the COMPARE algorithm and

demonstrated that the growth-inhibitory patterns of anticancer drugs against the cell lines

correlated well with their mechanism of action (Chabner and Roberts, 2005). A large

number of plant species have been screened through bioassays for search of novel plant

based anticancer drugs (Bibi et al., 2012). Examples of clinically useful antitumor agents

derived from plants include paclitaxel, vincristine, and camptothecin. Many of these plant-

derived anticancer agents have been discovered through large-scale screening (George et

al., 2010). Table 1 represents various drugs along with their plant origin, therauptic use

and mechanism of action.

The in vitro cytotoxicity assay gives us the information that active plant samples

causes reduction in the cancer cell number. The decrease in cell number may be due to

necrosis or apoptosis or inhibition of cell division. Necrosis has been characterized as

passive, accidental cell death resulting from environmental perturbations with

uncontrolled release of inflammatory cellular contents (Fink and Cookson, 2005).

Programmed cell death or apoptosis is a physiological process leading to the elimination

of useless and harmful cells, which is very important for preserving tissue homeostasis in

multicellular organisms (Segundo et al., 1999, Andersson et al., 2006). Furthermore,

apoptotic cell death is the consequence of a series of precisely regulated events that are

frequently altered in tumor cells. A brief description of differential features and

significance of necrosis and apoptosis has been summarized in Table 2.

The mechanisms of apoptosis induction are complex and not fully known, but

some key events are identified that appear essential for the cell to enter apoptosis

(Segundo et al., 1999, Andersson et al., 2006). The notion that apoptosis represents a

critical element in cell number control in physiological and pathological situations has

been reviewed and its role in oncogenesis is now well established (Hall, 1999). Apoptosis

is characterized by cytoplasmic condensation, plasma membrane blebbing and nuclear

pycnosis, leading to nuclear DNA breakdown into multiples of ~200 bp oligonucleosomal

size fragments. The detection of apoptosis in cultured cells relies heavily on techniques

involving the extraction of nuclear DNA and characterization of such oligonucleosomal

ladders by gel electrophoresis (Loannou and Chen, 1996). One of the hallmarks of

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apoptosis is the redistribution of phosphatidylserine (PS) from the inner-to-outer plasma

membrane (PM) leaflet (Mirnikjoo et al., 2009). This exposure of PS on the outer leaflet

of the membrane is the most-characteristic marker of an apoptotic cell (Armstrong and

Ravichandran, 2011).

Simon et al. (2000) reported the role of reactive oxygen species (ROS) and

mitochondria in apoptosis induction under both physiological and pathological conditions.

Interestingly, mitochondria are both source and target of ROS. ROS is also known to be

destructive to both DNA and proteins. DNA damage can be studied by BrdU incorporation

method. BrdU is incorporated into newly synthesized DNA and therefore labels

replicating cells. During this labeling period, BrdU is incorporated in place of thymidine

into the DNA. BrdU incorporation inhibition interpreted the DNA damage in newly

proliferative cells (Militao et al., 2006). Bearoff and Fuller-Espie (2011) stated that

mitochondrial membrane potential (��m) is the product of stored energy for the

mitochondrial respiratory chain maintained by a balance of ions such as sodium and

potassium within the mitochondrion. This potential difference normally exists at -180 to -

200 mV and is necessary for transport of precursor proteins into the mitochondrion. They

further stated that during early apoptosis the mitochondrial membrane becomes

depolarized leading to increased permeabilization and the release of mitochondrial

contents which, in addition to cytochrome c, contains a second mitochondria-derived

activator of caspases that initiate apoptosis through the deactivation of inhibitor of

apoptosis proteins. Previous work by Fan and co-workers (2005) suggested that

phosphorylated Bcl-2 and Bcl-XL proteins may potentiate apoptosis by controlling

mitochondrial cytochrome c release into the cytosol and subsequent activation of the

caspase cascade. Brenner and Mak (2009) also reported the role of Bcl-2 family of

proteins in regulation of apoptosis by controlling mitochondrial permeability. The anti-

apoptotic proteins Bcl-2 and Bcl-xL reside in the outer mitochondrial wall and inhibit

cytochrome c release. During apoptosis the proapoptotic Bcl-2 proteins residing in the

cytosol, translocated to mitochondria, where they promote the release of cytochrome c

(Rong and Distelhorst, 2008). The progress of apoptosis is regulated in an orderly way by

a series of signal cascades under certain circumstances. The caspase-cascade system plays

vital role in the induction, transduction and amplification of intracellular apoptotic signals.

Caspases, closely associated with apoptosis, are aspartate-specific cysteine proteases and

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members of the interleukin-1�-converting enzyme family (Fan et al., 2005). The two

major cellular routes, which are involved in cytotoxic chemical induced apoptosis, have

been identified, namely, the death receptor pathway and the mitochondrial pathway (Lin et

al., 2005). The extrinsic pathway is initiated through the stimulation of the transmembrane

death receptors, such as the Fas receptors, located on the cell membrane. In contrast, the

intrinsic pathway is initiated through the release of signal factors by mitochondria within

the cell.

In the extrinsic pathway, signal molecules known as ligands, which are released by

other cells, bind to transmembrane death receptors on the target cell to induce apoptosis.

For example, the immune system’s natural killer cells possess the Fas ligand (FasL) on

their surface (Csipo et al., 1998). The binding of the FasL to Fas receptors (a death

receptor) on the target cell will trigger multiple receptors to aggregate together on the

surface of the target cell. The aggregation of these receptors recruits an adaptor protein

known as Fas-associated death domain protein (FADD) on the cytoplasmic side of the

receptors. FADD, in turn, recruits caspase-8, an initiator protein, to form the death-

inducing signal complex (DISC). Through the recruitment of caspase-8 to DISC, caspase-

8 will be activated and it is now able to directly activate caspase-3, an effector protein, to

initiate degradation of the cell. Active caspase-8 can also cleave BID protein to tBID,

which acts as a signal on the membrane of mitochondria to facilitate the release of

cytochrome c in the intrinsic pathway (Adrain et al., 2002).

The intrinsic pathway is triggered by cellular stress, specifically mitochondrial

stress caused by factors such as DNA damage and heat shock (Hague and Paraskeva,

2004). Upon receiving the stress signal, the proapoptotic proteins in the cytoplasm, BAX

and BID, bind to the outer membrane of the mitochondria to signal the release of the

internal content. However, the signal of BAX and BID is not enough to trigger a full

release. BAK, another proapoptotic protein that resides within the mitochondria, is also

needed to fully promote the release of cytochrome c and the intra-membrane content from

the mitochondria (Johnstone et al., 2002). Following the release, cytochrome c forms a

complex in the cytoplasm with adenosine triphosphate (ATP), an energy molecule, and

Apaf-1, an enzyme. Following its formation, the complex activates caspase-9, an initiator

protein. In return, the activated caspase-9 works together with the complex of cytochrome

c, ATP and Apaf-1 to form an apoptosome, which in turn activates caspase-3, the effector

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protein that initiates degradation. Besides, the release of cytochrome c from the intra-

membrane space, the intra-membrane content released also contain apoptosis inducing

factor (AIF) to facilitate DNA fragmentation, and Smac/Diablo proteins to inhibit the

inhibitor of apoptosis (IAP) (Hague and Paraskeva, 2004). Diagrammatic illustration of

apoptotic pathway is represented in Fig. 1.

2.1 Anticancer agents from plants

2.1.1 Vinca Alkaloids: The beneficial properties of the Madagascar periwinkle plant,

Catharanthus roseus (L.) G. Don (formerly Vinca rosea) has been described in folklore in

various parts of the world. The plant yielded four active dimeric alkaloids; vinblastine,

vincristine, vinleurosidine and vinorelbine. Two of these, vinblastine and vincristine are

important clinical agents for treatment of leukemias, lymphomas and testicular cancer.

Another agent, vinorelbine, has important activity against lung cancer and breast cancer

(Budman, 1997). The vinca alkaloids, antimitotic agents, are asymmetrical dimeric

compounds and are cell-cycle specific agents. They are in common with other drugs such

as colchicine, podophyllotoxin and taxanes that block cells in mitosis. The vinca alkaloids

and several of their semi-synthetic derivatives block mitosis with metaphase arrest by

binding specifically to tubulin resulting in its depolymerization. The ability to bind

specifically to tubulin and to block the ability of the protein to polymerize into

microtubules is the basis of their action. Cell division is arrested in metaphase. In the

absence of an intact mitotic spindle, the chromosome may disperse throughout the

cytoplasm (exploded mitosis) or may clump in unusual groupings, such as balls or stars.

The inability to segregate chromosomes correctly during mitosis presumably leads to cell

death. Both normal and malignant cells undergo apoptosis (Smets, 1994). Vincristine is a

standard component of regiments for treating pediatric leukemia and solid tumor and

primarily in treating testicular carcinomas and lymphomas and as second-line therapy of

various solid tumors. Vinblastine and Vincristine are used clinically for over 40 years.

2.1.2 Epipodophyllotoxins: The development of the anticancer drugs, etoposide, and

teniposide, as semisynthetic derivatives of epipodophyllotoxin which was isolated from

the mandrake plant (may-apple; Podophyllum peltatum L. and P. emodii Wall (Cragg and

Newman, 2004). It was used as a folk remedy by the American Indians and early colonists

for its emetic, catharic and anthelmintic effects. It was isolated from the resin and found

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to be too toxic in mice. These derivatives are referred to as etoposide and teniposide.

Although podophyllotoxin binds to tubulin at a site distinct from that for interaction with

the vinca alkaloids, etoposide and teniposide have no effect on microtubular structure or

function (Hande, 1998; Pommier et al., 2001). Etoposide and teniposide are similar in

their actions and in the spectrum of human tumors affected. Unlike podophyllotoxin, they

do not arrest cells in mitosis; rather, these compounds form a ternary complex with

topoisomerase II and DNA. This complex result in double stranded DNA breaks, the

strand passage and resealing of the break that normally follow topoisomerase binding to

DNA are inhibited by the drug.

2.1.3 Taxane: A chemical discovered in the pacific Yew tree Taxus brevifolia is first drug

of choice in treating cancer. The development of paclitaxel, firstly isolated from the bark

of western yew tree in 1971 (Wani et al., 1971) as an effective drug for the treatment of

breast and ovarian cancers. Paclitaxel is a diterpinoid compound that contains a complex

taxane ring as its nucleus. The side chain linked to the taxane ring at carbon 13 is essential

for its antitumor activity. It binds specifically to the beta-tubulin subunit of microtubules

and appears to antagonise the disassembly of the key cytoskeleton protein, with the result

that bundles of microtubules and aberrant structures derived from microtubules appear in

paclitaxel treated cells. Arrest in mitosis follows. Cell killing is dependent on both, drug

concentration and duration of cell exposure. The taxanes, including paclitaxel and

derivatives, act by binding tubulin without allowing depolymerization or interfering with

tubulin assembly (Schiff et al., 1979; Horwitz, 2004).

2.1.4 Camptothecin: In the early sixties, the discovery of camptothecin by Wall and

Wani, 1996 as an anticancer drug with a unique mode of action, i.e. inhibition of DNA

topoisomerase I, added an entirely new dimension to the field of chemotherapy. This

naturally occurring alkaloid was first extracted from the stem wood of the Chinese

ornamental tree Camptotheca acuminate during the screening of thousands of plants in a

search for steroids (Diwakar and Gunjan, 2012). It shows anticancer activity mainly for

solid tumours. Camptothecin was approved by US Food and Drug Administration in the

1970s against colon carcinoma and thus it was evaluated as a possible drug in the

treatment of human cancer in phase I and phase II studies. Although camptothecin showed

strong antitumour activity among patients with gastrointestinal cancer, it also caused

unpredictable and severe adverse effects including myeloid suppression, vomiting,

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diarrhea, and severe haemorrhagic cystitis. These findings eventually resulted in the

discontinuation of phase II trials in 1972. But extensive research led to the development of

more effective derivatives, Topotecan and Irinotecan. Topotecan is used for the treatment

of ovarian and small cell lung cancers, while irinotecan is used for the treatment of

colorectal cancers. Topotecan and irinotecan exert their cytotoxic action through inhibition

of topoisomerase I, a fundamental enzyme complex involved in DNA ‘winding and

unwinding’ (Srivastava et al., 2005). According to Cragg and Newman (2004), despite

intensive research aimed at discovering other classes of compounds demonstrating

topoisomerase I inhibitory activity, only a few novel chemotypes have been identified.

These include the 2-aryl-quinoline derivatives (indenoquinolines), 3-arylisoquinoline

derivatives (indenoisoquinolines), and the naphthyridines which can be traced to the

protoberberine alkaloids, such as nitidine, isolated from Zanthoxylum and Fagara species

(Rutaceae).

2.1.5 Combretastatin: The combretastatins were isolated from the South African ‘bush

willow’, Combretum caffrum (Eckl. & Zeyh.) Kuntze (Combretaceae), collected in South

Africa in the 1970s as part of a random collection program for the NCI by the United State

Department of Agriculture, working in collaboration with the Botanical Research Institute

of South Africa (Pinney et al., 2005). The combretastatins are a family of stilbenes which

act as anti-angiogenic agents, causing vascular shutdown in tumors and resulting in tumor

necrosis. The most potent combretastatin A-4 is a simple stilbene that has been shown to

compete with colchicines for binding sites on tubulin. It has been found to be a potent

cytotoxic agent which strongly inhibits the polymerization of brain tubulin by binding to

the colchicine site. Combretastatin A-4 is thus an attractive lead molecule for the

development of anticancer drugs (Srivastava et al., 2005).

2.1.6 Colchicine: The alkaloid colchicine extracted from C. autumnale, binds to the

tubulin molecule, thereby inhibiting its assembly into microtubules and microtubule

dynamics. Tubulin-colchicine binding is slow, strongly temperature-dependent, and

practically irreversible. Bicyclic colchicine analogue 2-methoxy-5-(2',3',4'-

trimethoxyphenyl)-2,4,6-cycloheptatrien-1-one (MTC) induced a dose- and time-

dependent apoptotic response in human leukemic cells. MTC and colchicine rapidly

disrupted the microtubule integrity and arrested cells at the G2-M phase before the onset

of apoptosis (Gajate et al., 2000). Involvement of cytochrome c release and caspase-3

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activation during colchicine-induced cerebellar granule cell apoptosis was investigated by

Gorman et al. (1999). Treatment of rat cerebellar granule cells with 1 �M colchicine (for

up to 24 h) caused high molecular weight DNA fragmentation and nuclear condensation.

An involvement of group II caspases (which includes caspase-3) was demonstrated by the

proteolytic degradation of poly-(ADP-ribose)-polymerase (PARP) after 18 h exposure to

colchicine. Colchicine induced a time-dependent increase in Ac-Asp-Glu-Val-Asp-�-(4-

methyl-coumaryl-7-amide) (DEVD-MCA) cleavage activity in cerebellar granule cells,

which was blocked with a specific, peptide-based, aldehyde inhibitor of group II caspases,

i.e. DEVD-CHO. Activation of caspase-3 during colchicine-induced apoptosis may be

mediated by cytochrome c, since there was a close correlation between the time courses of

cytochrome c release from the mitochondria and of caspase-3 activation.

2.1.7 Ellipticine: Ellipticine and 9-methoxy ellipticine are pyridocarbazole (monomeric

indole) alkaloids that have been isolated from Ochrosia elliptica, which acts as potent

anticancer agent. Ellipticine and its derivatives are used to treat cancers of the breast and

the kidney. Lipophilic derivatives of ellipticine act by binding to the DNA (Sakarkar and

Deshmukh, 2011).

2.1.8 Indirubin: Indirubin is an antileukemic compound isolated from the Chinese

medicine Indigo naturalis (Qing-Dai), a blue pigment made from the leaves of

Baphicacanthus cusia, Indigofera tinctoria, Polygonum tingctorium or Isatis tingctoris

(Xiao, 1981). Qing-Dai has been used in the traditional Chinese prescription “Dang G I Lu

Hui Wan”, which is used in the treatment of chronic myelocytic leukemia. Indirubin and

its more potent water soluble synthetic derivative N-methylindirubin oxime have been

used for treatment of chronic myelocytic leukemia in china (Ma and Yao, 1983).

2.2 Some well reported plants having anticancer activity

Curcuma longa contains curcumin, which inhibits the growth of cancer by

preventing production of harmful eicosanoid such as PGE-2. The anticancer effect of

curcumin has been demonstrated in all the steps of cancer development, i.e. initiation,

promotion and progression of cancer. Data obtained from several studies suggest that

curcumin inhibits the genesis of cancer as well as promotes the regression of cancer

(Kikuzaki and Nakatani, 1993). Curcumin suppresses mutagenic effect of various

mutagens including cigarette smoke condensates, 7, 12-dimethylbenzanthracene (DMBA)

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and benzopyrene. Curcumin is found to decrease levels of urinary mutagens. It also

possesses anti-inflammatory and antioxidant properties. The protective effects of C. longa

and its derivatives are partially due to direct antioxidant effect. Studies have revealed that

C. longa inhibits production of nitrosamine that enhances natural antioxidant functions of

the body. C. longa increases levels of glutathione and other non-protein sulphahydryls. It

acts directly on several enzymes. Curcumin is used to treat squamous cell carcinoma of the

skin and the ulcerating oral cancer. C. longa also prevents malignant transformation of

leukoplakia. Its active phenolic constituents inhibit cancer and also have antimutagenic

activity. Turmeric has been shown to suppress the development of stomach, breast, lung,

and skin tumors (Nagabhushan and Bhide, 1992). Its activity is largely due to the

antioxidant curcumin (a diferuloylmethane), which has been shown to be an effective anti-

inflammatory agent in humans (Chan and Fong, 1994).

Withania somnifera contains withanolides, which possess immuno-modulatory

activity. Withaferin A and withanolide D found in W. somnifera are known to inhibit

growth of cancer. The other alkaloids presents in W. somnifera are ashwagandhine,

cuscohygrine, anahygrine, tropine, steroidal compounds, including ergostane type

steroidallactones, withasomniferin-A, withasomidienone, withasomniferols A-C, and

withanone. Other constituents include saponins containing an additional acyl group

(sitoindoside VII and VIII), and withanolides with a glucose at carbon (sitoindoside IX

and X). Apart from these contents, plant also contains chemical constituents like

withaniol, acylsteryl glucosides, starch, reducing sugar, hantreacotane and ducitol, Studies

have revealed that W. somnifera enhances the therapeutic effect of radiotherapy. The

chemopreventive activity is thought to be due in part to the antioxidant / free radical

scavenging activity of the extract. An in vitro study showed withanolides from W.

somnifera inhibited growth in human breast, central nervous system, lung, and colon

cancer cell lines comparable to doxorubicin (Sakarkar and Deshmukh, 2011).

Zingiber officinalis (ginger) rhizomes offer a rich package of gingerols-phenolic

antioxidants that possess pronounced anti-inflammatory activity-that inhibit various

cancers. Ginger also contains curcumin, which assist in the elimination of cancer causing

substances from the body. The anticancer properties of ginger are attributed to the

presence of certain pungent vallinoids, viz. [6]-gingerol and [6]-paradol, as well as some

other constituents like shogaols, zingerone etc. A number of mechanisms that may be

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involved in the chemopreventive effects of ginger and its components have been reported

from the laboratory studies in a wide range of experimental models (Nadkarni, 2002;

Kokate et al., 2006).

Betula utilis contains betulin that can be easily converted into betulinic acid.

Studies have revealed that betulinic acid inhibits growth of malignant melanoma and

cancers of the liver and the lung (Sakarkar and Deshmukh, 2011).

Camellia sinensis contains polyphenolics which are known to possess

antimutagenic and anticancer activity. Some evidence suggests that tea has a protective

effect against stomach and colon cancers. Animal studies also suggest that the risk of

cancer in several organs is reduced by consumption of green and black tea or their

principal catechins. The tumor incidence and average tumor yield in rats with chemically

induced colon cancer were significantly reduced when the rats received (-)-

epigallocatechin gallate, a major polyphenolic constituent of green tea. In a study

conducted at the New Jersey Medical School, extracts of both black and green tea

significantly inhibited leukemia and liver tumor cells from synthesizing DNA. Green and

black teas are also reported to possess antifungal, antibacterial, and antiviral activity. It

also inhibits growth of cancer by eliminating free radicals from the body. Gallates found in

green tea protect the body from damaging effects of radiation. A regular use of green tea

protects the body against many cancers including those of the liver, oesophagus, stomach,

intestine and the lung. It has been observed that daily consumption of 5 grams of green tea

inhibits synthesis of nitrosamine (a major carcinogen) in the body (Sakarkar and

Deshmukh, 2011).

Kumar et al. (2008) reported that an essential oil from a lemon grass variety of

Cymbopogon flexuosus (CFO) and its major chemical constituent sesquiterpene

isointermedeol (ISO) induce apoptosis in human leukemia HL-60 cells. CFO and ISO

inhibited cell proliferation with IC50 of ~30 and 20 �g/ml, respectively after 48 h

incubation. Both induced concentration dependent strong and early apoptosis as measured

by various end-points, e.g. annexinV binding, DNA laddering, apoptotic body formation

and an increase in hypo diploid sub-G1 DNA content during the early 6 h period of study.

The study demonstrated that it could be because of early surge in ROS formation with

concurrent loss of mitochondrial membrane potential. Both CFO and ISO activated apical

death receptors TNFR1, DR4 and caspase-8 activity. Simultaneously, both the isolates

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increased the expression of mitochondrial cytochrome c protein with its concomitant

release to cytosol leading to caspase-9 activation, suggesting thereby the involvement of

both the intrinsic and extrinsic pathways of apoptosis. Further, Bax translocation and

decrease in nuclear NF-�B expression predict multi-target effects of the essential oil and

ISO, while both appeared to follow similar signaling apoptosis pathways. The easy and

abundant availability of the oil combined with its suggested mechanism of cytotoxicity

makes CFO highly useful in the development of anti-cancer therapeutics (Kumar et al.,

2008).

Sharma et al. (2010) investigated the apoptosis inducing effect of essential oil (EO)

from aerial parts of O. viride in human colorectal adenocarcinoma cells (COLO 205 cell

line). The COLO 205 cells were exposed to 0.0125-0.1 �l/ml of EO for 24, 48 and 72 h.

Growth inhibition was determined by sulphorhodamine B (SRB) assay. Double staining

with acridine orange and ethidium bromide for nuclear changes was performed. Cell cycle

analysis and change in mitochondrial membrane potential was quantified by flow

cytometry. Subsequently, using annexin V/PI assay, the proportion of cells actively

undergoing apoptosis was determined. Changes in DNA were observed by DNA ladder

assay. Eventually, the surface morphology of apoptotic cells was studied by scanning

electron microscopy. They further stated that EO was cytotoxic to COLO 205 cells in dose

and time-dependent manner, as is evident by SRB assay. This observed cell death was due

to apoptosis, as established by annexin V/PI assay, DNA ladder formation and scanning

electron microscopy. Their results revealed that EO has apoptosis inducing effect against

COLO 205 cells in vitro and is a promising candidate for further anti-cancer study.

Cedrus deodara is also known as Devdar or Deodar. It is reported to be used as

carminative, astringent, febrifuge and has anticancer activity in human epidermal

carcinoma of throat. It is also applied to ulcers and skin diseases. Bhushan et al. (2006)

have reported AP9-cd, a standardized lignan composition from Cedrus deodara consisting

of (–)-wikstromal, (–)-matairesinol, and dibenzyl butyrolactol, showed cytotoxicity in

several human cancer cell lines. It inhibited Molt-4 cell proliferation at 48 h IC50 of ~15

�g/ml, increased sub-G1 cell fraction with no mitotic block, produced apoptotic bodies and

induced DNA ladder formation. Flow cytometric analysis of annexin V-FITC/PI-stained

cells showed time-related increase in apoptosis and post-apoptotic necrosis. All these

biological end-points indicated cell death by apoptosis. Further, initial events involved

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massive nitric oxide (NO) formation within 4 h, with subsequent late appearance of

peroxides in cells; measured by flow cytometry using specific fluorescent probes. AP9-cd

caused 2-fold activation of caspase-3 in Molt-4 and 5-fold activation in HL-60 cells. Also

caspases-8 and -9 were activated in HL-60 cells. The studies indicated that AP9-cd

mediated early NO formation leads to caspases activation, peroxide generation, and

mitochondrial depolarization which may be responsible for mitochondrial dependent and

independent apoptotic pathways involved in the killing of leukemia cells by AP9-cd

(Bhushan et al., 2006).

Boswellia serrata is Indian frankincense or Salai. A triterpenediol (TPD)

comprising of isomeric mixture of 3�,24-dihydroxyurs-12-ene and 3�,24-dihydroxyolean-

12-ene from Boswellia serrata induces apoptosis in cancer cells. Bhushan et al. (2007)

investigated that TPD inhibited cell proliferation with IC50 ~ 12 �g/ml and produced

apoptosis as measured by various biological end points e.g. increased sub-G1 DNA

fraction, DNA ladder formation, enhanced AnnexinV- FITC binding of the cells. Initial

events involved massive reactive oxygen species (ROS) and nitric oxide (NO) formation,

which were significantly inhibited by their respective inhibitors. Persistent high levels of

NO and ROS caused Bcl-2 cleavage and translocation of Bax to mitochondria, which lead

to loss of mitochondrial membrane potential (��mt) and release of cytochrome c, AIF,

Smac/DIABLO to the cytosol. These events were associated with decreased expression of

survivin and ICAD with attendant activation of caspases leading to PARP cleavage.

Furthermore, TPD upregulated the expression of cell death receptors DR4 and TNF-R1

level, leading to caspase-8 activation. These studies thus demonstrate that TPD produces

oxidative stress in cancer cells that triggers self demise by ROS and NO regulated

activation of both the intrinsic and extrinsic signaling cascades.

Plants under investigation viz. Erythrina suberosa and Anagallis arvensis belong

to family Fabaceae and Primulaceae respectively. Therefore, in the following section an

attempt has been made to review some other plants from these families which are already

explored and reported for their anticancer potential.

2.3 Plants belonging to Fabaceae having anticancer activity

2.3.1 Erythrina abyssinica

Nguyen et al. (2009) reported that bioassay-guided fractionation of the ethyl

acetate extract of the stem bark of Erythrina abyssinica resulted in the isolation of three

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new, along with 12 known pterocarpan derivatives. All the isolates were evaluated for

their inhibitory effects on protein tyrosine phosphatase-1B (PTP1B), as well as their

growth inhibition on MCF7, tamoxifen-resistant MCF7 (MCF7/TAMR), adriamycin-

resistant MCF7 (MCF7/ADR) and MDA-MB-231 breast cancer cell lines. Compounds

which exhibited PTP1B inhibitory activity (IC50 values ranging from 4.2+/-0.2 to 19.3+/-

0.3 µM) showed strong cytotoxic activity (IC50 values from 5.6+/-0.7 to 28.0+/-0.2 µM). It

was further suggested that pterocarpans could be considered as new anticancer materials

by PTP1B inhibition.

2.3.2 Erythrina addisoniae

Watjen et al. (2007) isolated six prenylated pterocarpans from the stem bark

of Erythrina addisoniae Hutch. & Dalziel, and analysed for pharmacological activity.

While calopocarpin, cristacarpin, orientanol c, and isoneorautenol showed only a weak or

moderate toxicity in H4IIE hepatoma cells (EC50-value >25 µM), the toxicity of

neorautenol and phaseollin was in the low micromolar range (EC50-value: 1 and 1.5 µM,

respectively). They further focused on these two substances showing that both increased

caspase 3/7 activity and nuclear fragmentation as markers for apoptotic cell death.

Neorautenol (10 µM, 2h), but not phaseollin induced the formation of DNA strand breaks

(comet assay). Further analysis of these substances may lead to new pharmacons to be

used in cancer therapy.

2.3.3 Erythrina vespertilio Benth

A new glucoalkaloid, vespertilioside, together with three known alkaloids,

including 11- �-methoxyglucoerysovine, erysotrine, and hypaphorine, were isolated from

the fruits of E. Vespertilio Benth. In addition, three known isoflavonoids, including

phaseollin, alpiniumisoflavone and phaseollidin, were identified from the plant stems.

The cytotoxic activity of all compounds was evaluated against a metastatic prostate cancer

cell line (PC3) and neonatal foreskin fibroblast (NFF) using a real-time label-free cell

analyser. Among the tested compounds, phaseollidin showed cytotoxic activities against

PC3 (IC50�=�8.83�±�1.87�µM) and NFF (0.64�±�0.37�µM) cell lines (Iranshahi et al., 2012).

2.3.4 Erythrina abyssinica Lam.

�� E. abyssinica Lam. is an important medicinal plant growing in Sudan; its seeds

were investigated for the first time for their alkaloidal constituents and biological activity.

The in vitro cytotoxicity of the crude alkaloidal fraction (CAF) against the cell lines HeLa,

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Hep-G2, HEP-2, HCT116, MCF-7 and HFB4 showed promising activity, with IC50 values

of 13.8, 10.1, 8.16, 13.9, 11.4 and 12.2�µg/mL, respectively. Bioassay-guided fractionation

and isolation of the CAF led to the isolation of five Erythrina alkaloids, identified as

erythraline, erysodine, erysotrine, 8-oxoerythraline and 11-methoxyerysodine. These were

evaluated for their in vitro cytotoxic activity against Hep-G2 which resulted in IC50 values

17.60, 11.80, 15.80, 3.89 and 11.40 µg/ml respectively. Furthermore, in vitro cytotoxic

activity against HEP-2 was evaluated, which resulted in IC50 values 15.90, 19.90, 21.60,

18.50 and 11.50 µg/mL respectively (Mohammed et al., 2011).

2.3.5 Erythrina mildbraedii

The linear congeners, scandenone, erysenegalinsein M, 5,4'-dihydroxy-2'-methoxy-

8-(3,3-dimethylallyl)-2'',2''-dimethylpyrano[5,6:6,7]isoflavone, and the angular isoflavone

eryvarin B, and two other compounds, fraxidin and scoparone from the stem bark of the

Cameroonian medicinal plant Erythrina mildbraedii, were evaluated against growth of

human breast, prostate, and endometrial adenocarcinoma cells. Isoflavones 1, 3 and 6

strongly inhibited the growth of all three cell lines, supporting the notion that a non-

oxidized isoprenyl group at C-8 is requisite for cytotoxic activity (Tchokouaha et al.,

2010).

2.3.6 Erythrina variegata

Based on the soluble MTT tetrazolium/formazan assay, Ohba et al. (1998)

evaluated the cytotoxicity of Erythrina variegata proteinase inhibitors in some tumor

hematopoietic stem cell lines. Among the proteinase inhibitors, EBI, which belongs to the

Bowman-Birk family of inhibitors, was cytotoxic in relatively differentiated cells such as

Molt-4 and Jurkat derived from acute T lymphoblastic leukemia (T-ALL) cells

specifically, but ETIa and ECI, which are classified into Kunitz family inhibitors, did not.

It was suggested that the differences in the cytotoxicity might be due to the molecular size

of the inhibitors. The succinylation of lysine residue(s) of EBI led to about 50% loss of the

trypsin inhibitory activity as compared with the authentic EBI. When Molt-4 cells were

incubated with this derivative, no significant cytotoxicity was observed. This suggests that

the proteinase inhibitory activity might be involved in the cytotoxicity of human tumor

cell lines.

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2.3.7�Cajanus cajan

Cajanol (5-hydroxy-3-(4-hydroxy-2-methoxyphenyl)-dgmethoxychroman-4-one)

is an isoflavanone from Pigeon pea [Cajanus cajan (L.) Millsp.] roots belonging to family

fabaceae. Luo et al. (2010) has investigated the anticancer activity of cajanol towards

MCF-7 human breast cancer cells and mechanism of cell growth inhibition of cajanol was

analysed by cell cycle distribution, DNA fragmentation assay and morphological

assessment of nuclear change, ROS generation, mitochondrial membrane potential

disruption, and expression of caspase-3 and caspase-9, Bax, Bcl-2, PARP and cytochrome

c measurement. Cajanol inhibited the growth of MCF-7 cells in a time and dose-dependent

manner. The IC50 value was 54.05 µM after 72 h treatment, 58.32 µM after 48 h; and

83.42 µM after 24h. Cajanol arrested the cell cycle in the G2/M phase and induced

apoptosis via a ROS-mediated mitochondria-dependent pathway. Western blot analysis

showed that cajanol inhibited Bcl-2 expression and induced Bax expression to disintegrate

the outer mitochondrial membrane and causing cytochrome c release. Mitochondrial

cytochrome c release was associated with the activation of caspase-9 and caspase-3

cascade, and active-caspase-3 was involved in PARP cleavage. All of these signal

transduction pathways are involved in initiating apoptosis.

2.3.8 Senna italica

Senna italica is a member of the Fabaceae family (subfamily Caesalpinaceae),

widely used traditionally to treat a number of disease conditions, such as sexually

transmitted diseases and some forms of intestinal complications. The acetone extract from

the roots of S. italica assayed for the in vitro anticancer activity using Jurkat T cells

inhibited the growth of cells in a dose- and time-dependent manner (Masoko et al., 2010).

2.3.9�Indigofera linnaei

Indigofera linnaei is belonging to the family Fabaceae and is a reputed indigenous

medicine. Methanol extract of I. linnaei was investigated against HeLa, Hep-2, HepG-2,

MCF-7, HT-29, Vero and NIH 3T3 cells by MTT assay. The extract exhibited strong in

vitro cytotoxicity against all the tested cancer cell lines, but it was found to be safe with

normal cells and support the ethnomedical use of I. linnaei (Kumar et al., 2011).

2.3.10 Glycyrrhiza glabra L.

Rathi et al. (2009) investigated the in vitro cytotoxic screening of standard 18 �-

glycyrrhetic acid and also for natural anticancer drug Glycyrrhiza glabra L. (Fabaceae)

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using three different extracts (chloroform, methanol and water) of the drug through MTT

method. Cell viability of previously identified 18 �-glycyrrhetic acid in three different

extracts of G. glabra L. was determined by two fold trypan blue method using two

different cell lines MCF7-cancerous and Vero-normal cell line and it was quantified

through HPTLC method. The results of the HPTLC study indicated that the amount of 18

�-glycyrrhetic acid into three different extracts (chloroform, methanol and water extract)

of G. glabra L. was 26.6, 12.5 and 5.6 �g/g, respectively. The percentage viability of two

different cell lines was 45.71% for Vero-normal cell line and 78.78% for MCF7-cancerous

cell line. IC50 values of standard 18, �-glycyrrhetic acid was 0.412±0.004 �M and those

for the three different extracts (chloroform, methanol and water) of G. glabra L. on MCF7

cell line were 0.4485±0.001, 0.9906±0.001 and 1.288±0.005 �M, respectively. From the

above result, it can be said that 18 �-glycyrrhetic acid could be considered as a potential

source of natural anticancer component and the percentage of which was higher in the

chloroform extract (Rathi et al., 2009).

2.3.11�Psoralea corylifolia L.

P. corylifolia (Fabaceae) is a widely used medicinal plant in China. Bioactivities of

one volatile fraction (fraction I) and three other fractions (fraction II, III, IV) from

methanol extract of P. corylifolia were evaluated by the cytotoxicity on KB, KBv200,

K562, K562/ADM cancer cells with MTT assay by Yi et al. (2011). Fraction IV

significantly inhibits the growth of cancer cells in a dose-dependent manner. The

IC50 values were 21.6, 24.4, 10.0 and 26.9, respectively. Psoralen and isopsoralen, isolated

from fraction IV, were subjected to bioactive assay and presented a dose-dependent

anticancer activity in four cancer cell lines (KB, KBv200, K562 and K562/ADM). The

IC50 values of psoralen were 88.1, 86.6, 24.4 and 62.6, while of isopsoralen were 61.9,

49.4, 49.6 and 72.0, respectively. Apoptosis of tumor cell significantly increased after

treatment with psoralen and isopsoralen. Induction of apoptotic activity was confirmed by

flow cytometry after staining with Annexin V/PI. These results suggested psoralen and

isopsoralen contribute to anticancer effect of P. corylifolia.

2.3.12 Ziziphus mauritiana (Lamk.)

Z. mauritiana (Lamk.) is a fruit tree that has folkloric implications against many

ailments and diseases. In vitro anticancer potential of seed extract of Ziziphus mauritiana

against different cell lines (HL-60, Molt-4, HeLa, and normal cell line HGF) by MTT

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assay as well as in vivo against Ehrich ascites carcinoma (EAC) bearing Swiss albino mice

was investigated by Mishra et al. (2011). The extract was found to markedly inhibit the

proliferation of HL-60 cells. Annexin and PI binding of treated HL-60 cells indicated

apoptosis induction by extract in a dose-dependent manner. The cell cycle analysis

revealed a prominent increase in sub G0 population at concentration of 20��g/ml and

above. Agarose gel electrophoresis confirmed DNA fragmentation in HL-60 cells after 3 h

incubation with extract. The extract also exhibited potent anticancer potential in vivo.

Treatment of EAC bearing Swiss albino mice with varied doses (100–800�mg/kg b.wt.) of

plant extract significantly reduced tumor volume and viable tumor cell count and

improved haemoglobin content, RBC count, mean survival time, tumor inhibition, and

percentage life span. The enhanced antioxidant status in extract-treated animals was

evident from decline in levels of lipid peroxidation and increased levels of glutathione,

catalase, and superoxide dismutase.

2.4 Plants belonging to Primulaceae having anticancer activity

2.4.1 Lysimachia thyrsiflora L.

The genus Lysimachia (family Primulaceae) comprises over a hundred species in

the world. Several plants of this genus have been used in traditional medicine of Europe

and Asia to treat diarrhoea, fever, arthritis, and were reported to possess analgesic,

antibacterial, anti-inflammatory, cytotoxic and molluscicidal properties. Podolak et al.

(2007) reported that methanol extract from the underground parts of L. thyrsiflora was

found to show cytotoxic activity in vitro (95% dead cells at 80 �g/mL).

2.4.2 Dionysia termeana

Amirghofran et al. (2007) have demonstrated the antitumor activity of D. termeana

(Primulaceae) a plant native to Iran. Cytotoxic activity of the extract on tumor cell lines

using MTT colorimetric assay was determined. Cell cycle analysis by flow cytometry and

DNA fragmentation analysis on sensitive cell lines was then carried out. Results obtained

indicated that the highest activity of D. termeana was against K562 leukemia cell line with

IC50 less than 20 µg/mL. 55% inhibition of Jurkat cells due to exposure to D. termeana

was found at 200 µg/mL of the extract. A549, a lung carcinoma cell, and Fen bladder

carcinoma cell line were less affected. In flow cytometry analysis, D. termeana

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induced apoptosis in the K562 and Jurkat cells. In DNA fragmentation analysis, the extract

produced ladder formation in both cells.

2.4.3 Oenothera biennis

Arimura et al. (2004) demonstrated that evening primrose extract (EPE)

(Primulaceae) induced apoptosis in Ehrlich ascites tumor cells (EATC), and this effect was

specific on tumor cells. Furthermore, their results demonstrated that EPE exposure elicited

a rapid increase in the activity of superoxide dismutase and intracellular peroxides levels.

These changes caused translocation of Bax to mitochondria and a subsequent release of

mitochondrial cytochrome c. However, no activation of caspase-3 was observed in EPE-

treated EATC. EPE triggers off induction of apoptosis, which is AIF-mediated and

caspase-independent. Furthermore, it was shown that EPE elicited a dose-dependent

accumulation of cells in the G1 phase and inhibited DNA synthesis.

2.4.4 Primula denticulata

Tokalov et al. (2004) investigated the effect of flavones from inflorescence shafts

and calyx of Primula denticulata (Primulaceae) on cell cycle progression, mitochondrial

membrane potential, and reactive oxygen species in human acute myeloid leukemia cells

(HL-60) by flow cytometry. The flavonol quercetin was included in the study as reference

compound because of its known cytostatic properties and its activity as radical scavenger.

Compared to quercetin the flavones induced little apoptosis (up to 40 µM), but despite

their low toxicity, the Primula flavonoids possessed strong cytostatic properties even at

low concentrations. The cell cycle distribution showed a characteristic time-dependent

shift, giving evidence of a generally short-lived effect of the test compounds in the

exposed cells. The antioxidative properties quantified according to two different methods

correlated with the number of hydroxyl groups. Whereas, quercetin strongly affected the

mitochondrial membrane potential, none of the Primula flavones showed a comparable

effect.

2.4.5 Androsace umbellata (Lour.)

Park et al. (2010) reported the antiproliferative effect of four isolated compounds

from n-BuOH soluble fraction of Androsace umbellata (Lour.) Merr. (Primulaceae) by the

sulforhodamine B assay against multidrug resistance (MDR; MES-SA/DX5 and

HCT15/CLO2) and non-MDR (A549, SK-OV-3, SK-MEL-2, MES-SA, and HCT15)

human tumor cell lines. All compounds exhibited strong cytotoxicity against non-MDR

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human tumor cell lines with IC50 values of 0.19-2.37 µM. MDR cells and non-MDR cells

had similar sensitivity to these compounds, however, MDR cells were highly resistant to

doxorubicin. Compounds 1-4 induced an increase in the percentage of Annexin V-binding

cells, indicating that compounds induced apoptosis in RAW 264.7 cells. Also, the

condensation of nuclei, a characteristic morphological change of apoptosis, was observed

in RAW 264.7 cells by the treatment with n-BuOH fraction, compounds 3 and 4,

respectively.

2.4.6 Lysimachia clethroides

Liu et al. (2010) isolated and identified 15 flavonoids from L. clethroides Duby

(ZE4). Their effect on cell viability was measured by MTT assay and apoptosis was

assessed by flow cytometry, Hoechst 33258 staining and COMET assay. It was noticed

that ZE4 could inhibit the growth of K562 cells significantly by induction of apoptosis.

Further, marked morphological changes of apoptosis, DNA fragmentation and single DNA

strand breakages were observed clearly after treatment of ZE4. Bcl-2 expression was

down-regulated remarkably while Fas, Trail and DR5 up-regulated

when apoptosis occurred.

2.4.7 Lysimachia japonica THUNB

Arisawa et al. (1989) isolated a cytotoxic alkyl-resorcinol from L. japonica

THUNB. (Primulaceae) and identified as grevillol. It was tested for cytotoxicity against

KB, B-16, PC-13, L-5178Y, P-388, and HEp-2 cells in vitro and found to be active.

Table 1. Plant derivatives used in cancer therapy

S. No. Plant Semi-synthetic

analogs of plant

derivatives

Experimental status Mechanism of action Reference

1. Catharanthus

roseus

Vindesine and

Vinorelbine

Leukemias, lymphomas, advanced

testicular cancer, breast cancer,

lung cancer and Kaposi’s sarcoma.

By mitotic block Cragg and

Newman, 2005

2. Catharanthus

roseus

Vinflunine

Reduced toxicity in animal models By mitotic block Okouneva et al.,

2003; Simeons et

al., 2008

3. Podophyllum

peltatum and

Podophyllum

emodi

Etoposide and

Teniposide

Lymphomas, bronchial and

testicular cancers.

Topoisomerase II

inhibition

Van Maanen et al.,

1988

4. Taxus brevifolia

Nutt, Taxus

baccata

Taxol®

Metastatic, breast, ovarian, lung,

prostate cancer and lymphoid

malignancies

Anti-mitotic action Kingston, 2007

5. Taxus brevifolia

Nutt, Taxus

baccata

Taxotere®

Used in patients resistant to

Paclitaxel

Anti-mitotic Hait et al., 2007

6. Camptotheca

acuminate

Topotecan

Epithelial ovarian cancer and

small cell lung cancer

DNA topoisomerase I

inhibition

Creemers et al.,

1996

7. Camptotheca

acuminate

Irinotecan

Metastatic and colorectal cancer DNA topoisomerase I

inhibition

Fuchs et al., 2006

8. Camptotheca

acuminate

Exatecan

Potential anti-tumor activity both

in vitro and in vivo

DNA topoisomerase I

inhibition

Mineko et al.,

2000

continued..

S. No. Plant Semi-synthetic

analogs of plant

derivatives

Experimental status Mechanism of action Reference

9. Camptotheca

acuminate

LE-SN-38

Various cancer cell lines DNA topoisomerase I

inhibition

Zhang et al., 2004

10. Berberis

amarensis

Berbamine

Chronic myeloid leukemia Caspase-3-dependent

apoptosis

Xie et al., 2009;

Xu et al., 2006

11. Hvdrastis

canadensis L.,

Berberineeris sp. &

Arcungelisia flava

Berberine

Osteosarcoma, lung, liver,

prostate and breast cancer

Not known Wang et al., 2011;

Patil et al., 2010

12. Tabebuia

avellanedae

Betalapachone

Breast cancer, prostate

cancer, lung cancer,

pancreatic cancer and

promyelocytic leukemia.

Inhibition of

topoisomerase I and II

Li et al., 2000; De

Almeida, 2009

13. Betula alba Betulinic acid

Exhibits anti-cancer

activity in humans

Triggers

mitochondrial

pathway of apoptosis

Fulda, 2008

14. Colchicum

autumnale and

Gloriosa superb L.

Colchicine Leukemic and solid tumors Anti-mitotic Dubey et al., 2008

15. Combretum

caffrum Kuntze

Combretastatin A-4 Phase II clinical trials Tubulin structure

disruption

Thomson et al.,

2006; Ley et al.,

2007

16. Cucurbitaceae

species

Cucurbitacin

Various cancer cell lines Inhibits signal

transducer/JAK 2

activity and activates

STAT3 pathway

Molavi et al.,

2008; Bernard and

Olayinka, 2010

continued..

S. No. Plant Semi-synthetic

analogs of plant

derivatives

Experimental status Mechanism of action Reference

17. Curcuma longa Curcumin

Colorectal cancer, multiple

myeloma and pancreatic cancer.

Exact mechanism of

action is still unknown

Sa et al., 2010;

Goel et al., 2008

18. Wikstroemia

indica

Daphnoretin

a) Ehrlich ascites carcinomas and

b) human hepatoma Hep3B cells.

a) suppression of

protein and DNA

synthesis

b) suppresses

Hepatitis B surface

antigen expression

Lu et al. 2011;

Diogo et al., 2009

19. Lupinus species,

Vicia faba,

Glycine max,

Psoralea

corylifolia

Diadzein and

Genistein

Genistein inhibits ovarian and

breast cancers and also chemically

induced cancers of stomach,

bladder, lung, prostate, colon and

blood.

Inhibits 3A 4-

mediated metabolism

and oxidative

metabolism

Kaufman et al.,

1997; Moon et al.,

2006; Dixon and

Ferreira et al.,

2002

20. Ochrosia

borbonica,

Excavatia

coccinea,

Ochrosia elliptica

Ellipticine

Various cancer cell types DNA intercalation

and inhibition of

topoisomerase II

Kuo et al., 2006

21. Rhizome of

rhubarb

Emodin

lung, liver, ovarian and blood

cancer

Apoptosis of cancer

cells by several

pathways

Huang et al., 2009

22. Amoora rohituka

and Dysoxylum

binectariferum

Flavopiridol

colorectal, non-small cell lung

cancer, renal cell carcinoma, non-

Hodgkin’s lymphoma, chronic

lymphocytic leukemia, and also

solid tumors

Inhibits cell cycle

progression at G1 or

G2 phase

Mans et al., 2000

continued..

S. No. Plant Semi-synthetic

analogs of plant

derivatives

Experimental status Mechanism of action Reference

23. Cephalotaxus

harrintonia,

C. hainanensis and

C. qinensis

Harringtonine

and

Homoharringtonine

Acute myeloid leukemia and

chronic myeloid leukemia.

Inhibition of protein

synthesis and chain

elongation during

translation

Cragg and

Newman, 2005;

Efferth et al., 2007

24. Chinese herb, Dang

Gui Long Hui Wan

Indirubin

Chronic myeloid leukemia Inhibits cyclin

dependent kinases

Nam et al., 2005

25. Euphorbia peplus

L.

Ingenol 3-o-

angelate

Actinic keratosis and basal cell

carcinoma

Causes necrosis of

tumor by the

activation of PKC

Hampson et al.,

2005

26. Ipomoeca batatas 4-Ipomeanol

Lung specific cancer in animal

models

cytochrome P-450-

mediated conversion

into DNA-binding

metabolites

Ancuceanu and

Istudor, 2004

27. Iridaceaelatea

pallasii and

Iris kumaoensis

Irisquinone

Good activity in transplantable

rodent tumors

Acts as a

chemosensitizer

Hazra et al., 2004

28. Plant isoflavone,

genistein

Phenoxodiol

Ovarian, prostate and cervical

cancer

inhibit plasma

membrane electron

transport and cell

proliferation

Herst et al., 2009

29. Saponins of

ginseng

PandimexTM

Advanced cancers of breast, colon-

rectum, lung, pancreas and solid

tumors

Cell cycle arrest and

acts as P-glycoprotein

blocker

Pan et al., 2010

30. Plant species like:

mints, cherries,

lavenders and

many others

Perillyl alcohol

Non small cell lung cancer,

prostate cancer, colon cancer and

breast cancer.

Exact mechanism is

yet to be identified

Pan et al., 2010;

Bardon et al.,

2002; Yeruva et

al., 2007

continued..

S. No. Plant Semi-synthetic

analogs of plant

derivatives

Experimental status Mechanism of action Reference

31. Erythroxylum

pervillei

Pervilleines

Yet to be done Inhibitors of

P-glycoprotein

Mi et al., 2001; Mi

et al., 2002; Mi et

al., 2003

32. Salvia prionitis

Hance

Salvicine

Malignant tumors Inhibition of

topoisomerase II

Deng et al., 2011

33. Centaurea

Schischkinii

Schischkinnin

In vitro experiments on Colon

cancer lines

Not known Shoeb et al., 2005

34. Centaurea

Montana

Montamine

In vitro experiments on CaCo2

colon cancer cell line

Not known Shoeb et al., 2006

35. Aglaia foveolata

Pannell

Silvestrol

Prostate, breast and lung cancers.

apoptosome/mitocho

ndrial pathway was

involved in triggering

extrinsic pathway of

programmed cell

death of tumor cells

Kinghom et al.,

2009; Kim et al.,

2007

36. Tripterygium

wilfordii Hook F

PG490-88

Prostate cancer Enhances the

antitumor effects of

cytotoxic and

chemotherapeutic

agents, thereby

induces apoptosis.

Liu, 2011

Adopted with modifications from Nirmala et al. (2011)

Table 2. Differential features and significance of Apoptosis and Necrosis

Observation Apoptosis Necrosis

Morphological features

Outset Shrinking of cytoplasm,

condensation of nucleus

Swelling of cytoplasm and

mitochondria

Plasma

membrane

Blebbing of plasma membrane

without loss of integrity Loss of membrane integrity

Chromatin Aggregation of chromatin at

the nuclear membrane No such aggregation

Organelles

Mitochondria become leaky due

to pore formation involving

proteins of the Bcl-2 family.

Disintegration (swelling) of

organelles

Vesicles Formation of membrane bound

vesicles (apoptotic bodies)

No vesicle formation, complete

lysis

Terminal Fragmentation of cell into

smaller bodies Total cell lysis

Biochemical features

Regulation

Tightly regulated process

involving activation and

enzymatic steps.

Loss of regulation of ion

homeostasis.

Energy input Energy (ATP)-dependent (active

process, does not occur at 4°C)

No energy requirement (passive

process, also occurs at 4°C)

DNA

Non-random mono- and

oligonucleosomal length

fragmentation of DNA (Ladder

pattern after agarose gel

electrophoresis)

Random digestion of DNA

(smear of DNA after agarose gel

electrophoresis)

Timing

Prelytic DNA fragmentation,

Release of various factors

(cytochrome-c, AIF) into

cytoplasm by mitochondria.

Activation of caspase cascade.

Alterations in membrane

asymmetry (Externalisation of

Phosphatidylserine)

Postlytic DNA fragmentation (=

late event in cell death)

Physiological impact

Extent Localized effect that destroys

individual cells.

Affects groups of contiguous

cells.

Induction

Induced by physiological stimuli

(lack of growth factors, changes

in hormonal environment)

Evoked by non-physiological

disturbances (complement

attack, lytic viruses,

hypothermia, hypoxia,

ischemica, metabolic poisons)

Phagocytosis Phagocytosis by adjacent cells or

macrophages. Phagocytosis by macrophages

Immune

system No inflammatory response

Significant inflammatory

response

Fig. 1. Diagrammatic illustration of Apoptotic Pathway