Flavonol glycosides with insecticidal activity from methanol extract of <i>Annona mucosa</i> leave

Abstract

Three flavonoids, quercetin 3-O-β-D-glucoside (1), quercetin 3-O-α-D-arabinoside (2) and kaempferol 3-O-β-D-galactoside (3) were isolated from the methanol leaf extract of Annona mucosa. Their structures were determined using physical and spectroscopic methods. compound 1 showed the highest activity against both S. zeamais and P. truncatus with LC50 values of 20.891 μg/ml and 22.241μg/ml, respectively though lower than the activity of deltamethrine a commercial insecticide used as a positive control. Compounds 2 and 3 gave moderate toxicities with LC50 values of 21.745 μg/ml and 24.926 μg/ml for compound 2 and 29.260μg/ml and 24.241μg/ml for compound 3 when tested against S. zeamais and P. truncates, respectively. compounds 1, 2 and 3 were also tested for anti-feedant activities against S. zeamais and P. truncatus and they exhibited interesting results. The activities were concentration dependent, increasing with increase in concentration. Quercetin 3-O-β-D-glucoside (1) showed the highest activities with AFI50 values 14.856 µg/ml and 16.79 µg/ml against S. zeamais and P. truncatus respectively (Figure 3). This actvity was close to but lower than the activity of azadirachtin a commercial antifeedant that had an activity of AFI50 of 12.146 µg/ml and 12.432 µg/ml against S. zeamais and P. truncates, respectively. Compounds 2 and 3 also exhibited relatively high antifeedant activities with values of AFI50 values 17.257µg/ml and AFI50 19.965µg/ml for compound 2 while values of AFI50 21.599 µg/ml and 20.149 µg/ml were obtained for compound 3 respectively, when tested against S. zeamais and P. truncatus respectively.