Identification of new limonoids from Swietenia and their biological activity against insects.
BACKGROUND: Natural limonoids are one group of compounds being studied for their insecticidal properties. To discover new limonoids with better activities, analogs were prepared via acylation and hydrolysis, and bioassayed. RESULTS: Analogs were identified using one- and two-dimensional (COSY, HMQC and HMBC) 1H and 13C NMR, IR and MS. 3-O-Isovalerylswietenolide (13) and 3-O-isobutyrylswietenolide (14) showed excellent antifeedant activity, with DC50 values of 0.19 and 0.009 mg L-1 respectively, compared with the natural limonoid swietenolide (80.6 mg L-1) against fourth-instar Spodoptera frugiperda (JE Smith) larvae. CONCLUSION: This work shows that limonoid analogs prepared through semi-synthesis can be used as lead compounds for the development of new insecticides.