Insecticial activity of acokanthera spectabilis fruits extracts against culex pipiens l. diptera:culicidae
2009
Abdel-Aty, A.S. | Zahran, H.E.M.
Fresh fruits of Bushman's Poison, Winter sweet, Acokanthera spectabilis, Apocynaceae shrub, a common species in Egypt were washed and divided to seven fractions using different solvent systems. These fractions were evaluated for their mosquitocidal effects against Culex pipiens 4. h larval instar. They showed different larval lethal effects and inhibition of both pupation and adult emergence. Fraction I (extracted with aqueous acetone) was the most effective with complete death of the treated larvae at 500µg/ml after 48 hours with LC50 values of 53.8 and 26.5µg/ml after 24 and 48 hours, respectively. It exhibited complete suppressing the alive larvae pupation and the adult emergence at 200 and 100 µg/ml, successively. Further chromatographic separation of the most active fraction on Silica gel lead to eight subtractions. Subfractions 2 and 4 were more toxic with complete killing of the treated larval population at 500 and 10 µg/ml. Their LC50 values were 54 and 22.5µg/ml compared with 10 and 10 µg/ml after 4 and 5 days exposure, respectively. Their LT50 values were 5.41, 4.74 and 3,73 compared with 1.93, 1.18 and 1.0 days at 10.50 and 100 µg/mL At 50 µg/ml, subfraction 2 reduced pupation to 11.1% while subfraction 4 completely suppressed it with complete stop of adult emergence. Both subfractions harshly suppressed the treated eggs hatchability. Subfraction 4 appeared to be the most effective on larval mortality, pupation and adult emergence. Its GC-MS analysis proved it as a cardenolide glycosides rich component.
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