Abstract
The chitin synthetase inhibitor plumbagin and its 2-demethyl derivative juglone were found to inhibit in a dose-response fashion the cytochrome P-450 dependent ecdysone 20-monooxygenase activity associated with adult femaleAedes aegypti, wandering stage larvae ofDrosophila melanogaster, and fat body and midgut from last instar larvae ofManduca sexta. The concentration of these naphthoquinones required to elicit a 50% inhibition of the steroid hydroxylase activity in all the insects was approximately 1×10−4 M.