FRACTION AND DETERMINATION OF CAPSAICINOIDS FROM RED PEPPER FRUITS WITH INSECTICIDAL ACTIVITY AGAINST MEALWORM, Tenebrio molitor, AND SUPERWORM, Zophobas morio

Abstract

Green chemistry has recently been an active area of research and it is expected to replace the chemical synthesis in agriculture. In this study, our attempt is to fractionate and determine the capsaicinoids from red pepper fruit to control mealworm Tenebrio molitor and superworm Zophobas morio. The methanol extraction of red pepper fruit (Capsicum annuum L.) effectively killed T. molitor and Z. morio at the concentration of 10000 ppm. The insecticidal activity of nhexane, dichloromethane and aqueous layers derived from the extract by liquid-liquid partitioning were evaluated. Among them, only dichloromethane layer showed insecticidal activity; whereas n-hexane and aqueous layers were inactive against tested pests. The dichloromethane layer was successively fractionated by silica gel column chromatography to afford insecticidal compounds. The chemical structures of active compounds in dichloromethane layer were elucidated by the analysis of NMR and MS spectroscopic data. The active compounds were determined to be as capsaicinoids and their insecticidal activity was also evaluated using the in vitro residual contact bioassay method. The extracts containing capsaicinoids were formulated into a suspension concentrate (SC) biopesticide and evaluated for efficacy against T. molitor and Z. morio. The biopesticide caused mortalities by 95-100 % against tested pests at 1000 µg/mL. The study results suggested that extracts containing capsaicinoids could be used as active ingredients for the preparation of the biopesticide to control insect pests thereby preserving stored products in sustainable agriculture.