In vitro antioxidant activity of Piper nigrum Linn.

The fractions R1, R2 and R3 obtained from pet ether extract of Piper nigrum Linn. (PEPN) were investigated for in vitro antioxidant activity.1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, superoxide anion radical, nitric oxide radical, and hydroxyl radical scavenging assays were performed. The free radical scavenging activity of the different fractions PEPN increased in a concentration dependent manner. R3 and R2 fraction of PEPN in 500µg/ml inhibited the peroxidation of a linoleic acid emulsion by 60.48±3.33% and 58.89±2.51%, respectively. In DPPH free radical scavenging assay, the activity of R3 and R2 was found almost similar. R3 (100µg/ml) fraction of PEPN inhibited 55.68±4.48% nitric oxide radicals generated from sodium nitroprusside whereas curcumin in the same amount inhibited 84.27±4.12%. Moreover, PEPN scavenged the superoxide radical generated by the Xanthine/Xanthine oxidase system. The fraction R2 and R3 in the dose of 1000µg/ml also inhibited 61.04±5.11% and 63.56±4.17% respectively, the hydroxyl radical generated by Fenton's reaction. The amounts of total phenolic compounds were also determined and 56.98µg pyrocatechol phenol equivalents were detected in one mg of R3.