Laboratory Assessment of Bio-efficacies of Phytochemical Extracts from Peels, Pulp and Seeds of Citrus Fruit Species Against <i>Anopheles Gambiae</i> and <i>Anopheles Funestus</i>

Abstract

This study assessed the bio-efficacies of phytochemical extracts from peels, pulp and seeds of citrus fruits species on adult Anopheles gambiae and Anopheles funestus under laboratory conditions. The assessment established the most potent extract(s) that could be adopted in  sustainable control of malaria vectors. The peels, pulp and seeds obtained from Citrus sinensis, Citrus aurantifolia, Citrus limonum, Citrus reticulata and Citrus vitis were air-dried for 21 days, avoiding contamination. They were ground into powder and stored in air-tight glass bottles. The volatile phytochemical oil extracts were obtained from the powdered materials by Soxchletextraction method using Diethyl ether as solvent at temperature range of 60^oC - 80^oC for 6 hours. The extracts were left overnight at Laboratory temperature of 28.5^oC to allow the remaining ether to  evaporate. Standard methods were used to carry out qualitative and quantitative characterization of the active compounds present. Five different concentration grades, 5%, 10%, 15%, 20% and 25%,were prepared volume for volume, from each extract stock. A mixture of 20 live active adult An. gambiae and An. funestus were released by means of an aspirator into each of the 5smallsquared-shaped cardboard boxes which had already been labeled according to the different concentrations. With the help of insecticide spray pumps, the boxes were sprayed,one after the other,with their corresponding concentrations of the extracts via their
fine-meshed netted holes and then blocked. The time each box was sprayed with the extract aerosol was noted. A control was set up with another set of five boxes, each containing the same 20 live and active adult An. gambiae and An. funestus, and sprayed respectively, with 5%, 10%, 15%, 20% and 25% concentrations of a commercial insecticide
(called “Kill All”). 10 minutes later, the boxes were opened to check for death of the mosquitoes, and the result was recorded. Apart from the 5% all other concentrations of the extracts from the peels, pulp and seeds of C. sinensis, the peels and seeds of C.reticulata and C. limonum, and the peels and pulpof C. aurantifolia and C. vitis, showed different degrees of mosquitocidal activity. These observed variations in the bio-efficacies of the different extracts could be attributed to the corresponding variations in their qualitative and quantitative bioactive compound contents. Therefore, phytochemical extracts, having proved efficacious on adult mosquitoes as demonstrated in this study, suggest that they can be successfully adopted in sustainable control of malaria.

Key words: Phytochemicalextracts,  Citrus  fruit  species, Anopheles gambiae, Anopheles
funestus,Bioefficacy