IN VITRO ANTIOXIDANT AND ANTIVENOM ACTIVITIES OF AQUEOUS AND CHITOSAN ENCAPSULATED ANNONA SENEGALENSIS BARK EXTRACTS AGAINST NAJA NIGRICOLLIS VENOM

Abstract

Snake envenomation is a neglected tropical disease responsible for thousands of deaths and morbidities annually. One of the most important venomous snakes in Nigeria is najanigricollis. Its enzyme constituent of the venom has been linked to fatal complications after being envenomated. Therefore, this study aimed to compare the in vitro antioxidant and antivenom activities of aqueous crude extract and chitosan-encapsulated extract of Annona senegalensis bark. In vitro antioxidant tests, DPPH radical and ferric reducing power tests, and in vitro antivenom tests, including phospholipase A2 and proteinase inhibition tests, were carried out using standard procedures. The extracts exhibited high DPPH radical-scavenging and ferric-reducing power; however, the encapsulated extract demonstrated greater activity, with IC50 values of 20.45 μg/mL and 7.45 μg/mL against DPPH radical and FRAP, respectively, compared to the crude extract (50.36 μg/mL). and 20.69 μg/mL. Furthermore, the extracts had significant inhibitory effects on the venom enzymes, with the encapsulated extract showing greater inhibition. The encapsulated extract showed stronger proteinase inhibition (IC₅₀ = 47.30 μg/mL) compared to the crude extract (IC₅₀ = 45.04 μg/mL). In comparison, the crude extract exhibited stronger phospholipase A₂ inhibition (IC₅₀ = 15.10 μg/mL) than the encapsulated extract (IC₅₀ = 30.14 μg/mL). This is the first study to assess the antivenom potential of A. senegalensis bark extract against N. nigricolli encapsulated in chitosan. These findings suggest that chitosan encapsulation enhances the extract's antioxidant activity and improves selected antivenom properties, highlighting its potential as a lead candidate for further development of plant-based therapies for snakebite envenomation.