In vitro and in vivo evaluation of antioxidant activity of Annona muricata stem bark extracts in Rattus norvegicus

The objective of this study is to evaluate the in vivo antioxidant potential of ethanol extract of Annona muricata against CCl₄ induced toxicity in rats as well as its in vitro antioxidant effect and lipid peroxidation. The extract was prepared by cold maceration using absolute ethanol. The in vitro antioxidant properties of the extract was determined using DPPH (2,2-diphenyl-1-picrylhdrazyl) radical and in vivo antioxidant enzymes were assayed to evaluate the biological activities of the extract. The polyphenol content are alkaloids, tannin, flavonoids and phenol. In the in vivo studies, the animals were grouped into three groups of 15 rats each. Group 1 served as control and received 1 mL/kg b.w of olive oil orally for 28 days. Group 2 rats were orally administered 1 mL/kg CCl₄ mixed with olive oil (1:10) daily for 28 days while group 3 rats were administered 1 mL/kg CCl₄ and 200 mg/kg b.w of Annona muricata stem extract. Three of the rats from each group were sacrificed on days 1, 8, 15, 22 and 28. The plant extract showed remarkable hepatoprotective and antioxidant activity against carbon tetrachloride (CCl₄) induced oxidative stress as revealed from serum enzyme markers. CCl₄ induced a significant rise (p < 0.001) in aspartate amino transferase, alanine amino transferase, alkaline phosphatase and malondialdehyde level in the serum with a reduction in catalase activity. Treatment of rats with the plant extract (200 mg/kg b.w) significantly altered both serum enzymes activities and oxidant levels to near normal against CCl₄-treated rats. The in vivo and in vitro rapid radical scavenging studies were positive for the stem bark extract. This study suggests that the possible mechanism of the exhibited biological activities of the extract may be due to free radical scavenging owing to the presence of polyphenols in the extract. The plant extract possesses, antioxidant, anti-lipid peroxidation effect and it is hepatoprotective.