Repellency Effects, Cytotoxicity Assessment and Chemical Compositions of Citrus limon Seeds Extracts and Fractions Against Anopheles gambiae sl Mosquitoes.

BACKGROUND

Citrus limon seeds have limited exploration, compared to other parts. The increasing prevalence of mosquito menace prompted the investigation into the repellent effects of the seed n-hexane extract and fractions of Citrus limon (Rutaceae) against adult Anopheles gambiae sl mosquitoes. The cytotoxicity and chemical constituents of the 100% n-Hexane Fraction (HF) were also evaluated.

METHODS

Successive extraction was done with cold-maceration using, n-hexane, Ethyl Acetate (EA) and methanol. The three solvent extracts were screened against Anopheles gambiae sl mosquitos, using human bait method, at doses, 1.5, 2.5 and 5.0 mg/ml and with Deet and acetone used as positive and negative controls respectively. The n-hexane extract was further fractionated with column chromatography. Ten fractions (100% nhexane, 10, 20, 30, 40, 60, 80% EA in n-hexane, 100% EA, 50% methanol in EA, and 100% methanol) were collected, and all tested at a single optimized dose of 5 mg/ml for 2 hr. The cytotoxicity and the chemical constituents of HF were determined using brine shrimp lethality test and gas chromatography-mass spectrometry respectively.

RESULTS

N-hexane extract and HF, both at 5 mg/ml, showed the most protective effect of 97.52 and 89.40% respectively, compared with standard (Odomos Deet) 100% activity, with no significant difference (p>0.05) between the three. HF was toxic with LC50 values of 29.2354 ppm. Thirty compounds representing 79.25% of HF were identified. Major compounds present in the fraction were heptadecanamine (8.31%), N-(3-methylbutyl) acetamide (7.89%), 2-ethyl- 1-hexanamine (6.65%).

CONCLUSION

This promising repellent activity further justified the traditional usage of Citrus limon as mosquito repellent.