Finaly Revew for Book

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Biological Effects of Ecdysteroids and Their Non Steroidal Agonist

Bisacylhydrazines A Review

RESHMA JOHN , RASHMI P.A, LINU MATHEW

*

School of Biosciences, Mahatma Gandhi University, Kottayam, Kerala Pin-686560

*Corresponding author email: [email protected], mob: +919447505690

Abstract

Ecdysteroids are polar steroid hormones controlling arthropod development and

reproduction. Ecdysteroids in plants are called phytoecdysteroids, their concentration in

plants are higher than that in insects. The isolation of phytoecdysteroids from plants has

initiated fruitful research leading to the discovery of new phytoecdysteroids. Ecdysteroids

possess a number of pharmacological, medicinal and agricultural applications. Ecdysteroids

agonist and antagonists are potential insect control agents and valuable tool for studying

ecdysteroid action. New agents to control insect pest species, interference with ecdysteroid

action is an attractive, and little exploited target. The purpose of the review is to summarise

the biological effects of ecdysteroids and its agonist and antagonists.

Key words: Ecdysteroids, agonist, antagonists, plant defences, bisacylhydrazines.

Introduction

Insect development is driven by the action of two hormone classes, the ecdysteroids

and the juvenile hormones (Riddiford, 1994; Gilbert et al., 2000; Thummel, 2002) and they

are primarily involved in the regulation of postembryonic development, which is

characterized by moulting and metamorphosis. Ecdysteroids are produced in the prothoracic

glands in larvae and in the reproductive organs in adults (ovaries and testis), and in the

abdominal integument of some insects (Hoffmann & Gerstenlauer 1997). In the larval stages,

20-hydroxyecdysone initiates the moulting and metamorphosis process in larvae, and

Juvenile hormone regulates these changes during the commitment period. Ecdysone, the first

ecdysteroid was isolated by Butenandt and Karlson in 1954 (Dinan, 2001), and its structure


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was identified by Huber and Hoppe (Hoppe & Huber 1965). Insects sporadically shed their

rigid external exoskeleton and then replace it to grow. This process is called ecdysisis or

molting (Gilbert, 2004). Insect molting is regulated via binding of the molting hormone (20-

hydroxyecdysone: 20E) to its receptor protein, the heterodimer of ecdysone receptor (EcR)

and ultraspiracle (USP). The 20E-EcR/USP complex binds to the ecdysone response element

in the promoter of target genes and regulates their transcription. The molting process is

initiated by an increase in the titer of 20E, the larva stops feeding and apolysis of the

epidermis from the old cuticle takes place leaving an ecdysial space that is filled with molting

fluid containing inactive chitinolytic enzymes. Meanwhile massive protein synthesis takes

place in the epidermal cells for deposition of a new cuticle (Riddiford, 1994;Dhadialla et

al.,1998). Decline in the titer of 20E leads to the activation of enzymes for the digestion of

procuticle underlying the old cuticle. After completion of this process moulting fluid is

reabsorbed and pre ecdysal tanning of the new cuticle takes place (Reynolds, 1987). Finally,

eclosion hormone and ecdysis-triggering hormone are released, when 20E titer is declined to

the basel level and these events lead to the ecdysis of the larva leaving behind the remnants of

the old cuticle (Truman et al., 1983; Dhadialla et al.,1998; Zitnanova et al., 2001). With the

completion of ecdysis, feeding resumes and endocuticular deposition continues during the

intermolt period. Every moult corresponds to the end of one growth stage and and the

beginning of another (Fig 1).


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Fig 1 The ecdysteroid titer in Drosophiladevelopment (Kozlova & Thummel ,

2000)

Phytoecdysteroids

Phytoecdysteroids are analogues of invertebrate steroid hormones (zooecdysteroids) that

occur in a wide variety of plant species (Bergamasco & Horn, 1983) (Table 1). Within a few

years of the isolation of ecdysone from insects, an array of compounds having structural

similarity to insect moulting hormones has been extracted from plants and because of plant

origin these compounds are called phytoecdysteroids. Subsequent research has revealed that

phytoecdysteroid occurrence is widespread (Dinan, 2004a) and their concentration in plants

is higher than that in insects. It appears that 56% of terrestrial plant species contain

significant levels of ecdysteroids ( Dinan, 2001). Most crop species do not contain detectable

levels of ecdysteroids, spinach (Spinaciaoleracea) and quinoa (Chenopodium quinoa) being

notable exceptions (Bthory et al.,1982; Grebenoket al.,1991;Dinan, 1995,Dinan ,2001). A

range of evidence exists in support that ecdysteroid concentrations are highest in tissues

which are most important for the survival of the plant or, in the case of annuals, of the species


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into the next generation (Dinan,2001).The concentration of phytoecdysteroids in plants are

increased by mechanical damage,insect herbivory or methyljasmonate treatment(Schmelz et

al.,1998,1999,2002). Phytoecdysteroids are apparently non toxic to mammals and have a

number of beneficial and pharmacological and medicinal applications (Dinan, 2001; Slama &

Lafont, 1995) which explain the usage of ecdysteroids containing plants in medicine. These

plant species are primarily represented byLeuzea carthamoides, Rhaponticum uniflorum, and

Serratula coronate, Cyanotis vaga, Ajuga turkestanica, Pfaffia paniculata, P.

iresinoides(Lafont & Dinan ,2003).

Table 1 Medicinal plants containing phytoecdysteroids

Plant species Family Parts containing

phytoecdysteroids

Concentration Reference

Achyranthes fauriei

Ajuga iva

Cyanotis vaga

Pfaffia iresinoides

Serratula tinctoria

Sida rhombifolia

Tinospora cordifolia

Amaranthaceae

Laminaceae

Commelinaceae

Amaranthaceae

Asteraceae

Malvaceae

Menispermaceae

Roots

Aerial parts

Leaves

Roots

Aerial parts

Aerial parts

Aerial parts

0.41.2mg/gdw

4.5 mg/g dw

7 mg/g dw

6.2 mg/g dw

1020 mg/g dw

0.82 mg/g dw

0.25 mg/g dw

Ogawa et al., 1974

Wessneret al., 1992

Santos et al., 1970

Nishimoto et al.,

1987

Rudel et al., 1992

Jadhav et al., 2007

Pathaket al., 1995

Chemical structure


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Ecdysteroid carbon skeleton is termed as cyclopentano-perhydro-phenanthrene with a

beta side chain at C 17,which is the product of terpene biosynthesis through mevalonic acid

,cholesterol and related sterols(Bathori & Pongracz, 2005). The whole side chain is kept in

the case of C27-C29 ecdysteroids. C19,C21 and C24are formed by the cleavage of the side

chain. Ecdysteroids contain cis A-B ring junction, a 7-en-6-one chromophore in the B

ring,addition of -hydroxyl group at C14 and -hydroxyl group at C3.The B-C and C-D ring

junctions are always trans. A-B ring junction is normally cis(5-H)and only rarely trans(5-

H). The methyl groups at C10 and C13 have a configuration(Adler & Grebenok

1999;Dinan, 2001;Bathori & Pongracz 2005; Reginaldo etal.,2008). The 14-hydroxy-7-en-

6-one chromophore result in a characteristic ultra violet absorption with max at 242 nm in

methanol(Dinan, 2001).Usually two to eight hydroxyl group are present on ecdysteroids. Any

carbon atom other than the C7, C15, and C18 carbons may be hydroxylated. Additional and

alternative double bonds may exist between the4-5, 8-9,9-11,12-13,14-15,24-25,25-26,24-28

carbons. A second oxo group may be located on C2, C3,C12,C17,C20,C22. Numerous

ecdysteroids exist with 5-OH,1-OH and 11-OH groups and all of these are phytoecdysteroids.

Ecdysteroids hydroxylated at C9,C12,C17,C19,C21,C24,C28 and C29 occur in plants.

Phytoecdysteroids may be found conjugated with both organic and inorganic acids,organic

alcohol and glycosides(Bathori & Pongracz, 2005). Both the phytoecdysteroid level and

structural diversity of plant ecdysteroids are surprising(Fig 2) . The number, location and the

position of the hydroxyl substituents explain the structural diversity of phytoecdysteroids.

Plants are capable of biosynthesising phytoecdysteroids from mevalonic acid. In many cases,

the biosynthesis of phytoecdysteroids has been demonstrated to proceed via cholesterol

and/or lathosterol (Adler & Grebenok, 1995). Current knowledge about the biosynthetic

pathway(s) for ecdysteroids in plants is limited.


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Fig 2 Structure of some Ecdysteroids

Role of phytoecdysteroids in plants

Phytoecdysteroids as Plant hormones

20-Hydroxyecdysone in nanomolar concentrations affected metabolic processes, including -

amylase activation, retardation of leaf senescence, having synergistic effect with auxin on

coleptile elongation, antagonizing the effects of gibberelic acid (Golovatskaya, 2004). 20HE

also altered germination, shoot growth, and root elongation in tomato (Bakrim et al., 2007).


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Exogenous phytoecdysteroids produced weak gibberilin like activity in dwarf mung bean and

rice bioassay(Drier &Tower,1988). There are examples of ecdysteroid induced growth and

proliferation, but there is very little evidence supporting to consider ecdysteroids as plant

hormone.

Phytoecdysteroids in Defence

Phytoecdysteroids may play a role in plant defense. Ecdysteroids (predominantly 20E) have

been shown to have a range of detrimental effects on the development and survival of a

number of insect species (Bombyx mori (Kubo et al., 1983),Pectinophora gossypiella (Kubo

et al., 1981, 1983), Spodoptera frugiperda (Kubo et al., 1981), Acrolepiopsis assectella

(Arnault & Slma, 1986; Harmatha, 2000), Agrius convolvulus (Tanaka & Naya, 1995),

including inhibition of growth, supernumerary larval instars, death without moulting, death

associated with promoted moulting and prothetely(Dinan et al., 2009). Detoxification of

ecdysteroids occur in certain species by conjugating it with fatty acid and blocking the C-22

hydroxyl group, which is important for the biological activity of ecdysteroids (Dinan &

Hormann, 2005; Dinan et al., 2009). Insect species like Heliothis virescens, H. armigera,

Locusta migratoria,Manducasexta, Spodoptera littoralis,Lacanobia olereaceae,Acherontia

atropos are remarkably tolerant to ecdysteroids in their diet (Dinan, 1998; Dinan et al.,

2009), while others are partially tolerent(e.g. Cynthia cardui, Tyria jacobaeae; Blackford &

Dinan, 1997b), but higher levels are toxic to them. Ecdysteroid sensitive species are deterred

from eating an ecdysteroid-containing diet that they die of hunger rather than consume

ecdysteroid-containing food (e.g.Inachis io; Blackford & Dinan, 1997b).

Extraction and isolation of phytoecdysteroids

Ecdysteroid extraction and purification is complicated due to their polar nature, poor

crystallisation properties and the purification strategy comprises of multistep procedure


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including extraction, prepurification and combination of one or more chromatographic steps.

Dried plant parts were extracted exhaustive with large volumes of methanol. Ten fold excess

of solvent usually methanol was used in this first step. The removal of both polar and apolar

contaminants can be done using fractional precipitation and solvent-solvent partition.

Fractional precipitation was done using acetone which removes the compound more polar

than ecdysteroids. Solvent- solvent partition was done using aqueous methanol and hexane,

the ecdysteroids remain in the aqueous methanolic phase, this process removes both lipohilic

and hydrophilic contaminants. Next step is solid phase extraction(SPE) which removes

certain compounds from ecdysteroids with similar polarity but difference in having their

aromatic ring. Usually polyamides is used as stationary phase in SPE ( Bathori , 2002).

Multistep chromatographic methods such as adequate combination of adsorption

chromatography, partition chromatography, size exclusion and reverse phase chromatography

are generally done for the final purification of ecdysteroid( Bathori ,1998). Ecdysteroid

content of plant samples was generally determined by the use of bioassay, radio

immunoassay (RIA), spectrophotometry, thin-layer chromatography or HPLC(Bathori et

al.,2000). HPLC is generally used in the last step of isolation of ecdysteroids for ,UV,MS

and NMR analysis. Fig 3 explain method for extraction and isolation of ecdysteroid from

Silence viridiflora( Toth & Bathori,2008). Phytoecdysteroid levels have been quantified by

an ecdysteroid-specifc radioimmunoassay (RIA) which detects compounds structurally

similar to ecdysteroids (Dinan, 1995a). Bioassay is dependent on biological activity detects

compounds having ecdysteroid-like (agonist) activity (Clemment & Dinan, 1991; Clemment

et al., 1993). Combination of these two assays provides a powerful tool for the analysis of

phytoecdysteroids.


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al., 1977). The Drosophila Kc cell line is one of the most well documented 20E-responsive

cell lines currently available and has been used in numerous studies examining the effects of

20E. The epithelial cell line from Chironomus tentans established by Wyss (1982), is

considered as a simplified model to study early events in ecdysteroid induced tissue

differentiation (Spindler-Barth et al., 1989, 1995; Spindler-Barth, 1991, 1993; Lammerding-

Ktippel et al., 1994) and cuticle formation. Chironomus cells do not synthesise moulting

hormone but metabolise added ecdysteroids very slowly. TheDrosophila imaginal disc cell

lines (Cottam &Milner1997) and Spodoptera frugiperda Sf9 (Lynn & Oberlander 1983;

Vaughn et al.,1997) cell line was also used to study and compare the effect of ecdysteroids

and bisacylhydrazenes. Dinan and co-workers (2001a) used D. melanogaster BII tumorous

blood cells to test different ecdysteroids and extracts with ecdysteroid agonistic or

antagonistic activities. This BII cell line did not metabolize ecdysone, (Dinan et al., 1985).

Changes in cell morphology and a reduction in cell density occur in the presence of

ecdysteroid agonist that can be assessed turbidometrically.

I n vitroproduction of phytoecdysteroids

Cell culture technique seems to be a good alternative for production of biologically active

ecdysteroids. The ability of several plant species to produce phytoecdysteroids in vitro was

first demonstrated in callus cultures ofAchyranthes fauriei and Trianthema portulacastrum

(Hikino et al., 1971, Ravishankar & Mehta, 1979). Phytoecdysteroids have also been isolated

from the culture filtrates of Ajuga turkestanica (Lev et al., 1990), A. reptans var.

atropurpurea (Matsumoto & Tanaka, 1991), Pteridium aquilinum (McMorris & Voeller,

1971) and Serratula tinctoria (Corio-Costet et al., 1996). Callus and suspension cultures of

A. turkestanica, synthesised 20E and turkesterone, the 20E concentration in the cells being

several times higher than that in the roots and leaves of the plants, whereas the turkesterone

concentration was somewhat lower than in the intact plant (Lev et al., 1990). Hairy root


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cultures ofAjuga reptans var. artropurpurea, Achyranthes fauriei, Pfaffia iresinoides and

Vitex strickeri (Matsumoto & Tanaka, 1991) produced phytoecdysteroids. A. reptans hairy

root clones were shown to synthesize 20E, norcyasterone, cyasterone and isocyasterone,

which are characteristic ecdysteroids of intact plant roots. The cell culture that produced

secondary metabolites are considered interesting model system for studies of biosynthesis

and physiological role of phytoecdysteroids, the available information on which is scanty.

Commercial availability of phytoecdysteroids

Today more than 140 different ecdysteroid-containing preparations are available on the

market(Fig 4). They ususally contain 20E, sometimes in combination with other ecdysteroids,

and they are proposed in particular for use by bodybuilders (Lafont & Dinan, 2003). These

preparations contain ecdysteroids isolated from just a few plant species, mainly Leuzea

carthamoides, Cyanotis arachnoidea ,Pfaffia sp.

Fig 4 Examples of commercially available preparations containing phytoecdysteroids and their Web

address.(http://www.myprotein.com/sports-nutrition/beta-ecdysterone/10529949.html

,http://www.rocksolidbodybuilding.com/Beta-Ecdysterone-supplement.html, http://astronutrition.com/sni-20-beta-hydroxy-120-

caps.html,http://www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-

Ecdysterone,www.nutrend-supplements.com)
http://www.myprotein.com/sports-nutrition/beta-ecdysterone/10529949.htmlhttp://www.myprotein.com/sports-nutrition/beta-ecdysterone/10529949.htmlhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://astronutrition.com/sni-20-beta-hydroxy-120-caps.html,http:/www.rebodybuilding.com/forum/scifit/13423-scifit-ecdysterone-300-reviews.html,Indiaprotein.com/Beta-Ecdysterone,www.nutrend-supplements.comhttp://www.myprotein.com/sports-nutrition/beta-ecdysterone/10529949.html


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Applications of phytoecdysteroids

Phytoecdysteroids are apparently non toxic to mammals and have a number of

beneficial and pharmacological and medicinal applications (Dinan, 2001; Slama & Lafont,

1995). Phytoecdysteroids display a wide range of biological activities which explain the

usage of ecdysteroids containing plants in medicine (Table 2).

Table 2 Medicinal applications of phytoecdysteroids

Pharmacological

effects

Effect of ecdysteroids Species/

cells

Reference

Protein synthesis Stimulatory effect on protein synthesis,

ingested ecdysteroids(5mg/Kg) increased

mRNA translation efficiency

Mice Otaka et al.,1968,

Dinan & Lafont ,2006

Antidiabetic effects 20E reduced induced

hyperglycemia,stimulates glucose

incorporation into glycogen and enhance

glucose utilisation by tissues.

Antidiabetic effects are known for

ecdysteroid containing plants used in

traditional medicine.

In vitro experiments demonstrate thatecdysteroids increase glucose consumption

in an insulin independent fashion.

Rat

Mouse

HumanHepatocytes

Uchiyama & Yoshida,

1974,Yoshida et al., 1971

Kutepova et al.,2001,

Wessneret al.,1992,Chen

et al., 2006.


Dinan ,2009

Hypocholesterolaemic

effects

Ecdysteroids reduce cholesterol level by

reducing biosynthesis,enhancing catabolism,

and promoting its conversion into bile acid.

Rats Uchiyama & Yoshida,

1974, Dinan ,2009,

Lupien et al., 1969,


Wound healing Ecdysteroid containing liposome promote

wound healing, 20E stimulate keratinocyte

differentiation.

In vitro,it has psoriasis inhibiting activity

Humans Detmaret al.,1994,

Lafont &Dinan,2003

,Dinan & Lafont ,2006

Growth and cell

proliferation

Ecdysteroids have been shown to increase

growth in a wide variety of animals

20E (5mg/Kg) administered accelerates

healing process after experimental bone

fracture.

Stimulates proliferation of human umbilical

vein endothelial cells

Stimulates erythropoiesis

Mice,Rats

Sheep,Pigs

Quails

Rats

Rats

Rats

Feldman et al.,2008

Lafont &Dinan , 2003


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Gene switches

The heterodimer of nuclear receptors,ecdysteroid receptor(EcR) and ultraspiracle(USP) an

homologue of the vertebrate retinoid X receptor considered as the functional ecdysteroid

receptor. The homologue of USP in animals and humans is the retinoid X receptor (RXR) .

EcR/USP complex interacts with specific ecdysteroid responsive elements in the promoter

region of ecdysteroid responsive gene to alter gene transcription activity( Dinan & Lafont

,2006). Ecdysteroid receptor is not a natural component of vertebrate cell,ecdysteroids are

nontoxic to vertebrates and ecdysteroids do not activate vertebrate steroid hormone receptors

even at very high concentrations. Ecdysteroids are successfully developed as an effective

inducer forEcR based gene expression system and are suitable technologies for tight control

transgene expression in mammalian cells(Lafont & Dinan ,2003). EcR based gene switches

have been successfully applied in animal models (Karzenowski et al.,2005,Galimi et

al.,2005,Hoppe et al.,2000), in functional genomics(Takeda et al.,2000), disease

models(Albanese et al.,2000) and are candidate systems for switch controlled human gene

therapy(Palli et al.,2005,Toniatti etal,2004,Goverdhana et al.,2005,) and feasibility has been

demonstrated for two ecdysteroid ligands: ponasterone A and muristerone A(Lapenna&

Dinan,2009).The non steroidal ecdysteroids agonist bisacylhydrazene are considered as an

alternative ligand to generate an ecdysteroid inducible gene switch systems.

Bisacylhydrazines

Disturbances in the normal course of molting and metamorphosis under the action of

exogenous ecdysteroids or substances mimicking their biological activity usually lead to the

insect death. Ecdysteroids has limited application in controlling arthropod pest because of its

chemical and metabolic instability, they are too polar to penetrate insect cuticle and too

expensive to synthesise on large scale (Dinan, 198;Lafont & Dinan 2009).


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Bisacylhydrazines are non steroidal agonist of 20E and exhibit their insectisidal activity via

interaction with the ecdysteroid receptor proteins. Bisacylhydrazines are more metabolically

stable in vivo than ecdysteroids and because they are true ecdysone agonists at the receptor

level, ingestion of bisacylhydrazines creates hyperecdysonism in susceptible insects, thus

inducing effects and symptomology of a molt event (Dhadialla et al.,1998, 2005). The larvae

ultimately die as a result of their inability to complete a molt, starvation, and desiccation due

to hemorrhage. Four potent analogs (tebufenozide, methoxyfenozide, halofenozide and

chromofenozide) are currently on the market (Fig 5, Table 3) as safer insecticides with

reduced mammalian toxicity. These insecticides have very good ecotoxicological profile,

having virtually no impact on most non target organisms including beneficial insects and

pollinators, (bees, predators and parasitoids), birds, fish and terrestrial invertebrates

(Dhadialla et al., 2005). The BAH insecticides also have low-toxicity to mammals making

them reduced risk materials for humans handling the products.

tebufenozide

methoxyfenozide

Chromofenozide

halofenozide

Fig 5 Chemical structure of bisacylhydrazine insecticides


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Table 3 Bisacylhydrazine ant their pest spectrum.

Common name Registered

names

Industry Pest spectrum

Tebufenozide

( RH-5992)

MIMIC,

CONFIRM

,ROMDAN

Rohm and Haas

Co.,a

DowAgroSciencesLLC

b

Lepidoptera specific

Chilo suppressalis,Cnapholocrocis medinalis

Lymantria dispar, Plusia spp.,

Pseudoplusia includes, Spodoptera spp.

Trichoplusia ni

Methoxyfenozide

(RH-2485)

INTREPID

RUNNER

PRODIGYFALCON

Rohm and HaasCo.,

aDow

AgroSciencesLLC

b


Heliothis spp.,Helicoverpa zea

Chromofenozide

(ANS-118,CM-001)

MATRIC

KILLAT

Nippon Kayaku,

Saitane,Japan and

Sankyo,Ibaraki, Japan


Spodoptera littura, Spodoptera exigua

Spodoptera littoralis ,

Cnaphalocrosis medinalis,Heliothis virescens

Chilo suppressalis

Halofenozide

(RH-0345)

MACH 2 Rohm and HaasCo.,a DowAgroSciencesLLCb

Lepidoptera, Coleoptera specific

Agrotis ipsilon,Spodoptera frugiperda

Popillia japonica

Ecdysterone antagonists

Ecdysterone antagonists inhibit the effect of ecdysterone. The compound azadirachtin from

the seeds of the tree Azardirachta indica,is a feeding inhibitor and growth disrupting

compound for most insect orders. Treatment of insects with azadirachtin frequently elicits a

delay or permanent block of molting. Molting failures are due to reduced ecdysteroid titre,(

Redfern et al., 1982) , and azadirachtin inhibits ecdysteroid secretion from the prothoracic

glands ( Sieber & Rembold (1983). Azadirachtin may also affect the metabolism of

ecdysteroids, for example by hindering the conversion of ecdysone into the hormonally more

active 20-hydroxyecdysone (Smith & Mitchell, 1988). Imidazole compounds, KK-42 (1-

benzyl-5-[(E)-2,6-dimethyl-1, 5-heptadienyl] imidazole) and KS-175 (4-

phenoxyphenoxypropyl imidazole), have been reported to inhibit ecdysteroid synthesis,


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leading to disrupted development( Smagghe ,2007). Cucurbitacins B and D, isolated from

seeds ofIberis umbellata (Cruciferae) and shown to be responsible for the antagonistic

activity of a methanolic extract of this species in preventing the 20-hydroxyecdysone (20E)-

induced morphological changes in the Drosophila melanogaster BII permanent cell line

(Dinan et al.,1997). Other compounds being considered for anti-ecdysteroid effects include

the brassinosteroids, , limonoids and triterpenes (Richter & Koolman 1991; Decombel et

al.,2005; Dinan & Hormann, 2005). Antagonists of ecdysteroid action in invertebrate systems

will be useful as biochemical probes for the investigation of the control of gene expression by

ecdysteroids as well as lead compounds for the development of new insect pest control agents

(Dinan, 1995; Keckeis et al., 2000).

Conclusion

Phytoecdysteroids are structural analogues of insect molting hormone ecdysone. They exert a

number of beneficial pharmacological effects on mammals and hundreds of ecdysteroid

containing anabolic preparations are available in the markets. Some ecdysteroids may provide

promising alternative to anabolic androgenic steroids in therapy, but their mode of action is

completely unknown. So it would be worthwhile to perform detailed clinical trials to evaluate

its importance as a medicine. In vitro culture with high potential activity seems to be a good

source for the production of biologically active phytoecdysteroids. Bisacylhydrazenes are non

steroidal agonist of 20-hydroxyecdysone and exhibit their activity via interaction with

ecdysteroid receptor proteins. These insecticides are safe to beneficial insects and have

benign ecotoxicological properties,they are selective in their mode of action and potentially

act only on target species.The effect of insect hormone ecdysterone analogues or agonists has

been widely studied to understand the regulation of insect development and recent

developments in these technologies should help in developing novel pest management

methods.


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References

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hormones in plantsa review,Lipids 30:257262.

2. Adler, J.H. and Grebenok R.J. 1999. Occurrence, biosynthesis, and putative role of

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