Azolla pinnata phytochemicals extraction methods and its larvicidal potential against Aedes aegypti and Aedes albopictus

Mosquito-borne diseases are life-threatening diseases which cause illnesses and death. Vector control has implemented control methods through chemical insecticides application, microorganisms, fish and amphibians as a control measure of these diseases. However, it causes environmental pollution, development of resistance in mosquitoes, health issues and high expenses for biological control method. Therefore, phytochemicals are imperative for vector control management. Targeting their larva is considered as an ideal method since it is easy to deal with in aquatic habitat. This study explores larvicidal effectivity of Azolla pinnata, extraction methods and the phytochemicals responsible for the larvicidal activity. The bioassay is following WHO procedure for larvicidal testing for each Aedes species. The selection of solvents and methods for extraction is crucial in extracting larvicidal phytochemicals. Hence, this study used three solvents which are methanol, acetone and hexane and two extraction method, maceration and soxhlet. The extracts, ranging from 1000 to 3500 mg/L, were exposed against two medically important vector mosquitoes namely, Aedes aegypti (L.) and Aedes albopictus (Skuse) (Diptera: Culicidae) for 24 hours and 48 hours. The identification of phytochemicals was conducted using GCMS-QP2010 Ultra (Shimadzu) fitted with Rtx-5MS capillary column. The methanol extract of A. pinnata showed the most effective larvicidal activity in Ae. aegypti for with LC50 of 863 mg/L followed by Ae. albopictus with 867 mg/L. Hexane extract showed the lowest larvicidal activity compared to acetone extract with the highest LC50 values in Ae. aegypti, 1758 mg/L and Ae. albopictus 2059 mg/L, respectively. Therefore, hexane has the least potential for the larvicidal activity. Acetone recorded LC50 of 1074 mg/L in Ae. aegypti while 1072 mg/ in Ae. albopictus. The larvicidal effectivity of A. pinnata based on solvent extracts were arranged as methanol> acetone> hexane from the highest to the lowest effectively. The selection of methanol for extraction with soxhlet method has successfully extracting larvicidal phytochemicals of A. pinnata compared to maceration method with the same methanol extracts. The high larvicidal activity was illustrated in both Aedes species compared with the maceration method with low LC50 have been depicted from soxhlet extract in Ae. aegypti and Ae. albopictus with 1093 mg/L and 1035 mg/L. The morphological aberrations observed were shrunken abdomen, pigmented cuticle, ruptured anal papillae, and disrupted midgut. This has revealed the phytochemicals of A. pinnata were efficient for Aedes larvicidal with their activities as endocrine disruptor, poisonous phytosterol and antimicrobial. Therefore, it proves phytochemicals of A. pinnata can be developed as a plant-based larvicide as an effective and greener approach for Aedes control programme