Mosquito borne disease is a major public health problem globally, particularly the tropics being the major spot in the spread of malaria. The development of resistance to chemical insecticides has necessitated the research and development of natural mosquito repellent. The aim of this study is to extract, characterize and test the larvicidal activity of essential oil, produce mosquito repellent using the essential oil as its active ingredient and study the bioefficacy of the produced repellent on mosquito. 200g of Ocimum basilicum was extracted by soxhlet extraction method using n-hexane as solvent and percentage yield of the extract was calculated and found to be 12.85%.
The essential oil extracted was characterized using FTIR and GC-MS. Production of mosquito repellent, larvicidal activity of essential oil and bioefficacy study of mosquito repellent were conducted. The FTIR spectral indicated the presence of C=O, C=C, C-H and O-H functional groups. GC-MS study showed 12 prominent peaks with retention time of 5.756, 5.914, 10.486, 16.871,17.947, 19.883, 19.974, 20.807, 21.020, 21.231, 21.712 and 22.008 indicating the presence of twelve phyto-constituents namely: 2,4-pentadienoic acid, butanedioic acid hydroxyl-dimetyl ester, pentanedioic acid 3-oxo-dimethyl ester, palmitic acid methyl ester, stearic acid, 13-tetradece-11-yn-1-ol, 9-octadecenoic acid methyl ester, 9-octadecenoic acid (Z), hexadecanoic acid, 9,12-octadecadien-1-ol (Z,Z), 9,12-octadecadienoic acid methyl ester and E-9-tetradecenoic acid.
The essential oil showed larvicidal activity on Anopheles mosquito larva at concentration of 3ml/L, 4ml/L and 5ml/L. The mosquito repellent produced showed increasing repellent efficacy against adult Anopheles mosquitoes with increasing concentration of the essential oil. Hence it was concluded that Ocimum basilicum has a good efficacy as a repellent to Anopheles mosquitoes when used as active ingredient. The FTIR spectral reveal the presence of functional groups present in the essential oil which correlates with phyto-constituent identified by GC-MS characterization, with 9-octadecenoic (14.62%) having the highest % composition.