Phytochemical screening and effectiveness of Dioscorea sansibarensis (Zanzibar yam) leaves, bulbils and yams powders were assessed as protectants of beans (Phaseolus vulgaris L.) against Bruchus chinensis beetle. 0.5 g of leaves powder on 50g of beans (0.99 w/w %) inhibited oviposition by 35.42% and yams powder reduced adult emergence from Ph. vulgaris by 37.03%. Bulbils powder showed less performance in all the bioassay activities. The bulbils powder yielded 13.17% of phenolic compounds, 5.97% of saponin and 1.44% of flavonoids. The leaves attained 1.35% of terpenoids while alkaloids were absent in the leaves, bulbil and yam powders. Thin layer chromatography confirmed the presence of saponins, terpenoids and phenolic compounds. Three spots of saponins were visualized in bulbils with retention factor (Rf) values of 0.61, 0.72, 0.82. Six spots of terpenoids were visualized in leaves with Rf values of 0.18, 0.29, 0.49, 0.63, 0.80, 0.84. Five spots of flavonoids were visualized in bulbils with Rf values of 0.51, 0.60, 0.69, 0.71, 0.81. Two spots of phenolic compounds were visualized in bulbils with Rf values of 0.37, 0.63. The deterrent activity by the leaves, bulbils and yams powders might be attributed to the presence of flavonoids, terpenoids, saponins and phenolic compounds in the plant materials.
Keywords: Bruchus chinensis, Phaseolus vulgaris, Dioscorea sansibarensis, leaves, bulbils, yams, anti-oviposition, reduction in adult emergence, phytochemical screening.