Ponasterone

While the above observation is interesting and could possibly have some implications for the control of the pink bollworm, the complexity of the steroid nucleus of ponasterone A and other molting hormone analogs and their weak insecticidal effect when applied topically or administered orally to most species of economically important insects may preclude their commercialization. The only commercial use of the molting hormone analogs thus far has been in the sericultural industry for the synchronization of cocoon spinning of silkworm colonies (17). 

Figure 6. Stereostructures of the Insect Molting Hormone, Ecdysterone, and a Plant Analog, Ponasterone A...

Figure 7. Electron Micrograph Illustrating Ecdysls Inhibition of a Larva of the Pink Bollworm, Pectlnophora gossyplella after Ingestion of 2 ppm Ponasterone A In an Artificial Diet (Magnification x 100)...

Ponasterone A was also the most potent of three phytoecdysones orally Injected Into fourth Instar ori larvae (Table 2). All of the larvae treated with >5 yg ponasterone A were Induced to Initiate molting (apolysls), but were unable to complete this molt due to an Inhibition of ecdysls. Thus, all of these ponasterone A-treated larvae died In the pharate condition. 

Table 2< Effects of fl-ecdysone as compared to cyasterone and ponasterone A when orally Injected to 4th Instar B, mopi, 25 larvae were used per treatment.

The role of phytoecdysones in this scheme is that of an Important component in a rather complex defensive strategy of some plants. Their presence in plants probably serves a limited, yet important, protective role. For example, cotton bolls bred with several ppm of ponasterone A would very likely be resistant to attack by pink bollworm. 

Matteuccia struthiopteris (L.) Todaro Jia Gou Ju (root) Ponasterone A, ecdysterone, palmitic acid, astragalin, caffeic acid, chlorogenic, vanillic acid, p-hydroxybenzoic, p-coumaric, ferulic, protocatechuic, beta-sitosterol, campesterol, filicin, stigmasterol, pterosterone.48-217 Tonic, lower blood pressure. 

Osmunda japonica L. Zi Kee Guan Zhong (Japanese royal fern) (whole plant) Ponasterone A, ecdysterone, custeodysine, ecdysone.33 Anthelmintic, treat inflammation of the salivary glands. 

Podocarpus macrophyllus (Thunb.) D. Don Luo Han Song (Southern yew) (stem bark, leaf, root, fruit) Pinene, camphene, cadinene, podocarpene, neocryuptomerin, kaurene, ecdysterone, ponasterone, makisterones, hinokiflavone, sciadopitysin, podocarpus flavones, macrephyllic acid, podototarin, totarol.54 For ringworms, blood disorders, tonic for heart, kidneys, lungs, stomach. 

Matteuccia struthiopteris (L.) Todaro. China Ponasterone A, ecdysterone, pterosterone, filicin.48 Tonic, lower blood pressure. 

K. Nakanishi, Past and present studies with ponasterones, the first insect molting hormones from plants , Steroids, 1992, 57, 649-657. 

Table 3 Imaginal disc bioassays, giving the concentration of ecdysteroid required for 50% evagination (EC50) and the IC50 or Kd value determined from a competion assay for specifically bound [3H]ponasterone A.

Calliphora vicinaa ponasterone A muristerone A 20-hydroxyecdysone makisterone A inokosterone... 

Figure 9 Generalised scheme for an ecdysteroid-regulated gene switch system RXR = retinoid X receptor, EcR = ecdysteroid receptor, EcRE = ecdysteroid response element, MuA = muristerone A, PoA = ponasterone A.

Table 6 Kd values for a range of ecdysteroids and two bisacylhydrazines in cell-free extracts of Bn cells. Competition assays were performed with [3H]ponasterone A (0.2 nM), followed by charcoal assay, to determine IC50 values, which were then converted to Kd values. Data taken from [143],...

PAGE polyacrylamide gel electrophoresis PE phytoecdysteroid polB polypodine B poA ponasterone A... 

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