In vitro antioxidant activity of three Piper species.

Reactive oxygen species are known to play a role in numerous pathological conditions, and antioxidants from plant sources have been of great help in modulating this effect. This study assesses the methanolic extracts of the leaves of three Piper species (Piper guineense Schum and Thonn., Piper nigrum L. and Piper umbellatum L.) (Piperaceae) for their polyphenolic concentration and free radical scavenging activity. The Folin-Ciocalteu method was used to assess the polyphenolic concentration while the reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide radical, hydroxyl radical, nitric oxide scavenging and metal chelating activities were employed in studying the radical scavenging activity of the extracts. All three spices exhibited a marked polyphenolic concentration and dose dependent free radical scavenging activity. The free polyphenolic concentration of the three spices was in the order P. umbellatum (15.9 +/- 1.9 mg/g) > P. guineense (12.6 +/- 0.3 mg/g) > P. nigrum (9.8 +/- 0.8). The three Piper extracts exhibited a 79.8-89.9% scavenging effect on DPPH, an 85.1-97.9% scavenging effect on nitric oxide at a dose level of 10 mg/ml and a 47.1-51.6% scavenging effect on superoxide radical at a dose level of 8 mg/ml extraction. Piper extracts also exhibited a 57-76.1% scavenging effect on hydroxyl radical at 5 mg/ml, a 0.4-0.6 reducing power and an 88.3-93.9% metal chelating activity at a dose level of 8 mg/ml of extract. Thus, these Piper species can play a role in the modulation of free radical induced disorders.