Add time:07/27/2019         Source:sciencedirect.com

Two stereoisomers of a castasterone/ponasterone A hybrid compound, the (20R,22R) and (20R,22S)-isomers of 2α,3α,20,22-tetrahydroxy-5α-cholestan-6-one, were synthesized stereoselectively and their binding activity to the ecdysteroid receptor was determined. From the concentration–response curve for the inhibition of the incorporation of tritiated ponasterone A into ecdysteroid receptor containing insect cells, the concentration (IC50) required to inhibit 50% of the incorporation of radioactivity into cells was evaluated. The IC50 values of the (22R)- and (22S)-isomers were determined to be 0.30 and 38.9 μM against Kc cells, respectively, indicating that the (22R)-isomer is about 100 times more potent than the corresponding (22S)-isomer. IC50 values of these compounds against lepidopteran Sf-9 cells were determined to be 0.36 and 12.9 μM, respectively. The molting hormonal effect was examined in a Chilo suppressalis integument system and the 50% effective concentration for the stimulation of N-acetylglucosamine incorporation into the cultured integument was determined to be 2.7 μM for the (22R)-isomer, while the (22S)-isomer was inactive. On the other hand, both isomers did not show brassinolide-like activity in the rice lamina inclination assay.

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