Research
Phytochemical Characterization and Insecticidal Property of Jatropha Plant
Phytochemical analysis on the pulverized leaf sample of Jatropha curcas as well as the insecticidal activity of the ethanolic leaf extract on Callosobruchus maculatus was carried out. The study investigated the mortality rate as a result of treatment of grains with the leaf extract at different dilutions of 20, 40, 60, 80 and 100mg/ml. These were tested against C. maculatus by treating 20g of bean sample with the extract and then infesting each in a plastic container with 20 adults of the insect and the untreated grains were used as the control. The plant extract resulted in a significant increase (P<0.001) in adult mortality at the end of 96 hours but there was no significance difference (P=0.084) after 24 hours. The result had a general dose-response characteristic. There was also significant variation in the phytochemical composition of the plant leaf. Compared to other phytochemicals, the concentration of saponin and tannin were higher in the plant leaf.
The Synergistic Larvicidal Activities of Three Local Plants on Aedes Aegypti
The synergistic activity of extracts of Lantana camara, Stachytarpheta indica and Allamanda blanchetii against Aedes aegypti mosquito larvae were investigated. Ethanolic leaf extracts of these plants were tested separately and combined on Ae. aegypti larvae with concentration ranging from 5, 10, 20, 30 and 40mg/ml. In 72 hours bioassay experiment, mortalities were observed at the different time intervals but were highest at 40mg/ml concentration for the three plants independently, with the L. camara extract showing better larvicidal activity over the other plant extracts at 48 hours and 72 hours exposure. The LC50 of L. camara (6.08mg/ml), S. indica (8.15mg/ml) and A. blanchetii (6.44g/ml) indicates their ability to cause 50% larval mortality at such low concentrations. For the synergistic effects, all the concentrations exhibited high mortality at 48 hours and 72 hours exposure. The 40mg/ml showed the highest larvicidal activity (100% mortality) after 48 hours exposure with the L2:A1:S1 combination. Synergistic factor (S.F.) of 1.00, 1.27 and 0.94 were obtained for L. camara, S. indica and A. blanchetii. Synergism was recorded for L. camara and S. indica, while antagonism was recorded for A. blanchetii. Phytochemical analyses showed the presence of some active compounds including flavonoids, tannins, saponins, alkaloids and cardiac glycosides which may account for their mosquitocidal effects and at same time present them as an effective replacement to chemical insecticides. Combination of plant extracts is therefore strongly recommended to serve as a better mosquitocidal agent over the use of individual plant in mosquito control programs.
