Plant natural products as insect steroid receptor agonists and antagonists

Findings to date on plant secondary compounds which possess ecdysteroid-like or anti-ecdysteroid activities in an efficient and effective bioassay based on an ecdysteroid-responsive insect cell-line are summarised. Several novel antagonists have been identified, among which the cucurbitacins are the best characterised and have been shown to compete with ecdysteroids for the ligand binding site of the insect steroid hormone receptor. Certain withanolides, limonoids and resveratrol derivatives also antagonise 20-hydroxyecdysone action. Additionally, several new phytoecdysteroids have been isolated and identified, In common with all other ecdysteriods, these possess agonistic activity in the B-II bioassay. Extensive SAR studies based on the potencies of a large number of purified ecdysteroids have been performed and molecular (CoMFA) modelling used to characterise ecdysteroid binding to the ligand binding site of the receptor complex. (C) 1999 Society of Chemical Industry.