Activity Guided Fractionation of Ethanol Extract of Meriandra bengalensis against Anopheles Mosquito Larvae

Abstract

Aim: To prevent proliferation of mosquito borne diseases, to improve quality of life, mosquito control is essential. Research was aimed to find alternative eco-friendly and bio-degradable strategies in mosquito control at the larvae stage. Hence an attempt was made to study the larvicidal effect of the various column fractions of the ethanol extract of leaves of Meriandra bengalensis against late instar larva. Methods: Dried and powdered leaves of Meriandra bengalensis were extracted with hexane and ethanol by continuous refluxing. Extracts were filtered and concentrated on rotary evaporator. Column chromatography was used to partially purify the ethanol extract using Alumina. Various polar fractions; 2%, 4%, 6%, 8% and15% chloroform in petroleum ether and 10% methanol in chloroform were used to elute the active fractions. Larvicidal activity of various fractions at the 5 mg/ml and 2.5 mg/ml were recorded over 24 hour period. Larvae of Anopheles gambie were used for this study. Results: All fractions showed very high larvicidal potential, Difference in larvicidal activity was observed with in the first 4 hours but later all fractions had a 100% mortality rate at both concentrations. At 5 mg/ml and 2.5mg/ml the strongest larvicidal activity was shown by the chloroform: pet ether (6%) which was equally active as the standard treatment. In the negative control all larvae were active and motile. Conclusion: The findings of present study revealed that the column fractions of Meriandra bengalensiscontain effective larvicidal agents. Further investigations are needed to elucidate this activity against a wide range of all stages of mosquito species and also the active ingredient(s) of the extract responsible for larvicidal activity should be identified.