Insecticidal meliacarpins (C-seco limonoids) from Melia azedarach

Three new meliacarpin derivatives. namely 1,3-dicinnamoyl-11-hydroxymeliaca rpin. 1-cinnamoyl-3-methacryl-11-hydroxymeliacarpin and 1-cinnamoyl-3-acety l-11-hydroxymeliacarpin, were isolated as the principal insecticidal and gr owth disrupting constituents of Melia azedarach leaves. Their structures we re unambiguously established on the bads of MS spectrometric and NMR spectr oscopic data (H-1,C-13. COSY. H-1-detected direct and long-range C-13-H-1 c orrelations) and by comparison with known compounds. The insecticidal prope rties of the new meliacarpin derivatives were examined using larvae of the polyphagous pest insect Spodoptera litroralis. When incorporated into artif icial diet and offered to lan ae in a chronic feeding bioassay, 1-cinnamoyl -3-acetyl-11-hydroxymeliacarpin exhibited an EC50 of 0.27 ppm and a LC50 of 0.48 ppm and is thus comparable with regard to insecticidal activity to th e well known natural insecticide azadirachtin. Further-more. all three meli acarpin derivatives had a pronounced detrimental influence on larval metamo rphosis. (C) 1999 Elsevier Science Ltd.;lll rights reserved.