Insect antifeedants from tropical plants II: Structure of zumsin

A novel A-seco limonoid was isolated from methanolic extract of Croton jatrophoides and designated as zumsin. This compound showed potent antifeedant activity against two lepidopteran larvae, pink bollworm, Pectinophora gossypiella (PC50 = 1 mug/cm(2), PC95 = 8 mug/cm(2)), and fall armyworm, Spodoptera frugiperda (PC50 = 2 mug/cm(2), PC95 = 16,mug/cm(2)). The structure of zumsin was determined as 1 using a variety of spectroscopic methods including nuclear magnetic resonance, mass spectrometry, and circular dichroism. The structure consists of an A'-B trans-fused ring while dumsin (2), a constituent of the same source, maintains an A'-B cis-fused ring, and suggests two unique biosynthetic processes after A ring oxidative expansion.