The present study was carried out to evaluate the antioxidant activities of Cissus multistriata(Vitaceae) fruit in various system. Nitric oxide radical, 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical, and in vivo antioxidant enzymes were assayed to evaluate the biological activities of the extract. The percentage antioxidant activity of the methanol extracts increased in a concentration dependent fashion. In DPPH radical scavenging assays the IC50 value of the unripe fruit extract was 0.684 µg/ml. The ripe fruit extract inhibited the nitric oxide radicals generated from sodium nitroprusside with an IC50 of 0.184 µg/ml, comparable to 0.0161 µg/ml for standard vitamin C. The polyphenol contents of the extracts were also determined and the plant extracts contain tannins, flavonoids and anthocyanins. In vivo antioxidant and rapid radical scavenging activities were also screened which were both positive for the two fruit extracts. This study suggests that possible mechanism of the biological activities may be due to free radical-scavenging and antioxidant characteristics which may be due to the presence of polyphenols in the fruit extracts.
Key words: Antioxidant, DPPH, polyphenols.