Lethality of Naja nigricollis Reinhardt venom and antivenom activity of Azadirachta indica A. Juss. leaf extracts on albino rats

Snakebite remains an important cause of morbidity and mortality in Nigeria. Conventionally, the means of treatment is parenteral administration of serum-based antivenins. But due to the limitations of these antivenins, snakebite victims in many Nigerian communities are mostly treated with herbal antidotes. Hence, this research was designed to evaluate the lethality of Naja nigricollis Reinhardt venom and screen the antivenom activity of Azadirachta indica A. Juss. leaf extracts with a view to replacing the serum-based antivenin. The methanol extract of A. indica leaf was screened against venom-induced lethal effect in albino rats using standard methods. The crude methanol extract was subjected to solvent-fractionation, and the fractions were also screened against the venom-induced lethal effect in albino rats. The lethal doses, 50% (LD₅₀) and 100% (LD₁₀₀) of the venom were 0.389 and 3.891 mg/kg b. wt. respectively. The crude extract and its fractions exhibited antivenom activities with varying degrees of efficacy. The crude methanol extract and its hexane and ethyl acetate fractions presented animal mean survival time of 22.51 ± 2.38 h, 23.68 ± 0.89 h and 21.98 ± 1.36 h respectively against LD₁₀₀ of the venom. These are significantly different when compared with the mean survival time of the venom control groups. Hence, these findings suggest that A. indica leaf has potent antivenom activity and this can serve as leads for the development of safe, readily available and affordable antivenoms.