Antifeeding activity of limonoids from Khaya senegalensis (Meliaceae)

Fifteen B,D-secolimonoids of mexicanolide, rearranged phragmalin, methyl angolensate and glycoside types have been isolated from ether and acetone extracts of the stem bark of Khaya senegalensis (Desr.). The antifeedant activity of the isolated compounds was assessed by conventional choice leaf disc method on the third-instar larvae of Spodoptera littoralis (Boisd.). Khayalactol, 1-O -acetylkhayanolide A, 2-hydroxyseneganolide, khayanolide A, khayanolide D and methyl angolensate displayed strong antifeedant activity at 1000 mug/ml with antifeedant percentages of 83.8, 61.9, 60.1, 59.5, 57.1 and 55.7, respectively. 2-Hydroxyseneganolide and khayanolide D showed high activity at 500, 300 and 200 mug/ml while 1-O -acetylkhayanolide A was the only compound that revealed antifeedant activity at a concentration as low as 100 mu g/ml. Antifeedant activity was dose-dependent in some of the isolated compounds. Correlation between antifeedant activity of the isolated compounds and chemical structure was discussed.