STRUCTURE-RELATED INSECT ANTIFEEDANT AND GROWTH-REGULATING ACTIVITIESOF SOME LIMONOIDS

Insect antifeedant and growth-regulating activities of 22 limonoids (b oth natural and their derivatives) against Spodoptera litura were stud ied to understand the structure-related bioactivities of the limonoids . The C-seco limonoids (azadirachtins A, B, D, H, and I) were the most effective compounds as a group, while the intact limonoids (cedrelone and its derivatives) were the least effective. The cyclohexenone A ri ng and the alpha-hydroxy enone group in the B ring appear to be import ant for antifeedant activity. The presence of a cyclohexenone or 1,2-e poxide in the A ring coupled with an alpha-hydroxy enone in the B ring correlated well with growth regulatory activity. An acetoxy at C-7 in stead of or-hydroxy enone and perhaps the carbonyl at C-16 increase gr owth regulatory activity. Absence of 14-15 epoxide may not drastically reduce antifeedant activity and growth regulatory activity.