INSECTICIDAL ALKALOIDS AGAINST DROSOPHILA-MELANOGASTER FROM NUPHAR-JAPONICUM DC

In the course of screening for novel naturally occurring insecticides from Chinese crude drugs, MeOH extract of rhizomes of Nuphar japonicum DC. was found to give an insecticidal activity against larvae of Dros ophila melanogaster Meigen. Four alkaloids, (-)-7-epi-deoxynupharidine (1), (-)-castoramine (2), (-)-nupharolutine (3), and (-)-nupharmine ( 4), were isolated by bioassy-guided fractionation from the extract. In secticidal activity against larvae of D. melanogaster was demonstrated ; 2 and 1 showed LC50 values of 1.00 and 4.33 mu mol/mL of diet concen tration, respectively. Acute toxicity against adults of D. melanogaste r was also found; 1 had the most potent activity, with an LD50 value o f 0.86 mu g/adult. 1, 2, and 3 caused acetylcholinesterase inhibitions , at 0.5 mmol/L, of 99.6, 65.0, and 59.7%, respectively; however, 4 ha d only slight activity in this study. Therefore, 1 and 2 were identifi ed as insecticidal compounds from rhizomes of N. japonicum DC. Structu re-bioactivity relationship study indicated the importance of the posi tion of the hydroxyl group and the piperizine skeleton for enhanced ac tivity.