Inokosterone activity

Ecdysone Itself and the phytoecdysones, inokosterone and maklsterone A, were much less effective as abortifacients than 20-0HE (Table I). Cyasterone and ponasterone A were inactive the implication being that the hydroxyl group on C25 is required for activity (10). 

PE-free callus from Polypodium vulgare was shown to biotransform ecdysone fo 20-hydroxyecdysone, which is the last step in the biosynthetic pathway of the main plant PE. This hydroxylation is catalysed by a cytochrome P450 enzyme which was subsequently purified from that source (Canals et al, 2005). In another study, Reixach et al. (1999) have shown that 25-deoxy-20-hydroxyecdysone was transformed efficiently in both tissues into 20-hydroxyecdysone, but no 25-deoxyecdysteroids such as pterosterone and inokosterone were formed. Likewise, incubation of 2-deoxyecdysone produced exclusively ecdysone and 20E, indicating a high 2-hydroxylase activity in both tissues. 

Several active, related derivatives of ecdysterone (81) can be isolated from insects as well as from several plants and from the marine crab, Callinectes sapidus. Most of them differ with respect to the side chain. Characteristic examples of this type are ponasterone A (92), inokosterone (93), pterosterone (94), makisterone A (95) and cyasterone (96) (Scheme 1.28). 

---