Discovery of Insect Antifeeding Limonoids from Trichilia connaroides.

Exploration of the Trichilia connaroides led to the isolation of 16 previously undescribed limonoids (1-16). Compounds 1 and 2 were characterized by polycyclic caged seco-phragmalin frameworks, while 8 possessed a trans-fused B/C ring system. An insect antifeedant bioassay against Spodoptera exigua demonstrated that compounds 2, 11, 12, and 16, at a concentration of 0.005 mg/cm2, exhibited potent antifeedant effects comparable to that of azadirachtin and showed no appreciable cytotoxicity toward murine AML12 hepatocytes.