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Journal Article 
In vitro antioxidant activity of Piper nigrum Linn 
Singh, R; Rao, HS 
Pharmacognosy Magazine
ISSN: 0973-1296 
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 500 mu g/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 (100 mu g/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 1000 mu g/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 56.98 mu g pyrocatechol phenol equivalents were detected in one mg of R3. 
Lipid peroxidation; phenolic compounds; Piper nigrum