New insect-growth-regulator meliacin butenolides from the leaves of Azadirachta indica A. Juss

Abstract

Two new triterpenoids, 23-O-methylnimocinolide [7α-acetoxy-6α-hydroxy-23ξ-methoxy-3-oxo-24,25,26,27-tetranorapotirucalla(apoeupha)-1,14,20(22)-trieno-21,23-lactone] 1, 7-O-deacetyl-23-O-methyl-7α-O-senecioylnimocinolide [6α-hydroxy-23ξ-methoxy-3-oxo-7α-senecioyloxy-24,25,26,27-tetranorapotirucalla(apoeupha)-1,14,20(22)-trieno-21,23-lactone] 2 have been isolated from the methanolic extract of the fresh leaves of Azadirachta indica (neem). Their structures were elucidated through spectral studies, including 2D NMR (NOESY, COSY-45, HMQC and HMBC). Compounds 1 and 2 show insect-growth-regulating effect on mosquitoes (Aedes aegypti) with LC₅₀ 53 ppm and 2.14 ppm, respectively. The senecioyloxy substituent at C-7 in 2 results in a significant increase of activity.