MOSQUITO LARVICIDAL POTENCY OF SELECTED HALOPHYTE SPECIES AND THEIR MODULATION ON ACETYLCHOLINESTERASE AND GLUTATHIONE S-TRANSFERASE AGAINST DENGUE VECTOR: Aedes aegypti

Abstract

A mangrove is an ecosystem that represents a natural product reservoir of biotechnological  interest. They have been advocated as environmentally benign alternatives to synthetic pesticides against all vector mosquitos. The purpose of this study was to determine the larvicidal activities of selected mangrove plant extracts against Aedes aegypti mosquito larvae. Methanol extracts of three selected halophytes viz. Lumnitzera racemosa, Bruguiera cylindrica, and Excoecaria agallocha were made, phytochemically investigated and evaluated against A. aegypti early 4th instar larvae. Acetylcholinesterase (AChE) activity and Glutathione S-transferase (GST) activity were evaluated, followed by DNA extraction and fragmentation tests. GC-MS technique was used to determine the presence of bioactive chemicals. Alkaloids, flavonoids, terpenoids, anthocyanin, coumarins, phenolic compounds, and quinones were found in all plants. The best larvicidal activity was recorded in the L. racemosa flower buds (LC50- 0.766 mg/ml) and E. agallocha stem extract (LC50- 0.986 mg/ml).  L. racemosa flower buds and E. agallocha stem exhibited higher inhibition in Acetylcholinesterase (AChE) activity with the rate of 1.39 μmol ACT/min/mg protein and 1.65 μmol ACT/min/mg protein (p < 0.05) in treated larvae. In the case of L. racemosa flower buds, however, enhanced GST activity was detected. Plant extracts were found not to cause any fragmentation activity in the larval DNA. 5 major peaks of chemical compounds were analyzed in L. racemosa and E. agallocha. Because of the possible larvicidal action of selected halophyte extracts, they can be utilized as ecologically friendly mosquitocide for eradicating dengue vector larvae in their early stages.