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 (Meliaccae). 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 an of the tested concentrations (7.5-100 mg kg-1). Khayanolide B was the most potent antifeedant with an EC50 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 EC50 of 6.96 mg kg -1. © 2003 Society of Chemical Industry.