Limonoids from Aphanamixis polystachya and Their Antifeedant Activity

Eight new aphanamixoid-type aphanamixoids (C–J, 1–8) and six new prieurianin-type limonoids, aphanamixoids K–P (9–14), along with 10 known terpenoids were isolated from Aphanamixis polystachya, and their structures were established by spectroscopic data analysis. Among the new limonoids, 13 compounds exhibited antifeedant activity against the generalist Helicoverpa armigera, a plant-feeding insect, at various concentration levels. In particular, compounds 1, 4, and 5 showed potent activities with EC₅₀ values of 0.017, 0.008, and 0.012 μmol/cm², respectively. On the basis of a preliminary structure–activity relationship analysis, some potential active sites in the aphanamixoid-type limonoid molecules are proposed.