Feeding deterrent and growth inhibitory properties of limonoids from Khaya senegalensis against the cotton leafworm, Spodoptera littoralis

Three rearranged phragmalin‐type limonoids, khayanolide A, khayanolide B and 1‐ O ‐acetylkhayanolide B, and a mexicanolide‐type limonoid, khayalactol, have been isolated from the stem bark of Khaya senegalensis (Desr) A Juss (Meliaceae). The antifeedant and growth‐inhibitory activities of the isolated compounds were evaluated on Spodoptera littoralis (Boisduval). When added to an artificial diet, khayanolide A, khayanolide B and 1‐ O ‐acetylkhayanolide B showed antifeedant activity in a concentration‐dependent manner. Khayalactol exhibited strong antifeedant activity without significant differences at all of the tested concentrations (7.5–100 mg kg −1 ). Khayanolide B was the most potent antifeedant with an EC 50 of 2.19 mg kg −1 . The results also revealed that the isolated compounds caused marked larval growth inhibition on S littoralis after 7 days of feeding on treated diet; this effect was concentration‐dependent. Khayanolide B was the most active growth inhibitor among the isolated compounds, with an EC 50 of 6.96 mg kg −1 . Copyright © 2004 Society of Chemical Industry