Inhibitory effect of crude ethanol and water extracts of phytolacca dodecandra (l’ herit) on embryonic development of anopheles gambiae (diptera: culicidae)

Abstract

Plant extracts have been demonstrated to interfere with activities of juvenile hormones that facilitate egg hatching by the embryo. In the present study we demonstrate ovicidal effect of crude ethanol and water extracts of mature green fruits and leaves of Phytolacca dodecandra against Anopheles gambiae eggs under ambient laboratory condition. Freshly laid An. gambiae eggs were exposed to 33.33mls of water and ethanol extracts of mature green fruits and leaves of shoot and midsections of P. dodecandra. The solutions were a serial dilution of 40, 20, 10, 5 and 5mg/100mls of the crude extracts dispensed in plastic containers measuring 6cm top × 5.7cm bottom × 3.5cm height. Ovicidal activity was assessed 48 hours post exposure under dissecting microscope (Leica Zoom 2000) at ×10 magnification. Unhatched eggs were judged dead when non-hatched and with unopened opercula and alive when hatched or with open operculum. WHO threshold of > 80 % mortality was used to assess ovicidal effectiveness. Crude water extracts of leaves of the shoots killed more than 80% while ethanol extracts of the same parts killed 60% of exposed eggs. Leaf extracts of the shoots were more effective compared to extracts of leaves of midsection and mature green fruits. Egg mortality was higher for P. dodecandra extracts compared to Neem or deltamethrin. It was concluded that water extracts were more potent as ovicides than ethanol extracts irrespective of part of P. dodecandra used. Extracts of P. dodecandra can be used as an alternative to chemical insecticide in malaria vector control.