Evaluation for Feeding Deterrents Against Sitophilus zeamais (Motsch.) from Tithonia diversifolia (Hemsl.) A. Gray

Abstract Using bioactivity-guided isolation of bioactive compounds; deacetylviguiestenin, 4-O-caffeoyl-2-methyloxirane-2-carboxylic acid and sandaracopimaradiene-1α,9α-diol were obtained from Tithonia diversifolia (Hemsl.) A. Gray leaves and identified using spectroscopic methods. Their feeding deterrence activity against Sitophilus zeamais (Motsch.) including those of methanol crude extract, fractions, and the essential oil was determined. Results showed that the essential oil of T. diversifolia could not show significant anti-feedant activity at a dose of ˂0.29 μL/mg of flour disks. The solvent crude extract, some fractions and the isolated compounds, however, demonstrated feeding deterrence against S. zeamais. The feeding deterrence index of sandaracopimaradiene-1α,9α-diol was 81.19 ± 5.94% at 0.1% w/w (1 mg/g food) compared to 97.45 ± 0.43% for neemazal extract (10% azadirachtin) (positive control) at 10%w/w (100 mg/g food). The EC50 of deacetylviguiestin, 4-O-caffeoyl-2-methyloxirane-2-carboxylic acid and azadirachtin (commercial antifeedant) against S. zeamais were 22140.23 ± 9103.29, 3654.28 ± 2715.09 and 14.59 ± 5.59 ppm respectively. Although these compounds showed less activity against S. zeamais compared to azadirachtin, their anti-feedant activity was significant and are valuable alternatives.