STUDIES ON IDENTIFICATION OF TROPICAL PLANT CHEMICALS AND THEIR APPLICATION AS A NEW PEST CONTROL AGENTS

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MeOH extracts of rhizome of a tropical yam, Dioscorea hispida was separated into alkaloid and nonalkaloid fractions, and their active components were purified based on the feeding deterrent activity against Plutella xylostella. From alkaloid fraction of the extract, dioscorin (mw : 221) and dioscorin N-oxcide (mw : 237) were isolated as feeding deterrents. Dioscorin was more active than dioscorinN-oxcide at 100to 25mug/ml. Both alkaloids significantly retarded larval development, and showed high mortality at larvae and pupae. Non-alkaloid fraction also inhibited larval feeding, and chemical analysis of active compounds in the fraction is under way. Sikimi, Illicium anisatium is known to be a toxic plant to mammals. We ectracted the toxic compounds based on the insecticidal activity against the Culex quinquefasatus from the seed of Sikimi and performed the patch clamp experiments to clarify the mode af action at ion channel level. Crude MeOH extract of the seed was toxic to mosquito larvae, its LC_<50> value was estimated to be 63.0mug/ml. The toxicity moved to AcOEt fraction when the crude extract was partitioned into water and AcOEt, LC_<50> of the active fraction increased to 43.7mug/ml. The AcOEt fraction exerted a suppresive effect on GAGA-induced Cl current at 1 mug/ml.