Inhibition of Snake Venom Enzymes and Antivenom Adjuvant Effects of Azadirachta indica A. Juss. (Meliaceae) Leaf Extracts

Snake venom enzymes are the key substances involved in snake venom toxicity. Thus, inactivating these enzymes is generally considered to be the fundamental step in the management of snakebite. Conventionally, snakebite envenomation is treated parenterally with serum-based antivenins, and adjuvants to these antivenins are required for maximum protection of victims. Hence, this research was aimed at evaluating the inhibitory effect of Azadirachta indica leaf extracts on Naja nigricollis Reinhardt venom enzymes and screens for their antivenom adjuvant effects. A. indica leaf was collected, authenticated and extracted using 95% methanol followed by fractionation using hexane and ethyl acetate. The venom enzymes inhibition assays was evaluated using in vitro methods, while, adjuvant effect was screened using Albino rats. The results revealed that both the hexane and the ethyl acetate fractions showed capability of inhibiting the venom enzymes significantly (P<0.05) when compared with the venom controls in varying degrees of efficacies. For the adjuvant effect, no significant effect (P>0.05) of the venom at the administered dose was observed on bleeding time, clotting time, defibrinogenating and haemorrhagic effects compared to the normal control. However, the size of necrotic lesion and the percentage haemolysis were significantly (P<0.05) higher in the venom control rats. Both the hexane and the ethyl acetate fractions significantly mitigated these effects in the treated animals. The degree of protection was about 3 folds more than when the antivenin was used alone. Finally, these findings would be of importance in the area of drug development with a view to actualizing the substitution or enhancing the effect of conventional snakebite therapeutic options.