Abstract

The aim of this study was to evaluate the free-radical scavenging capacity and antioxidant activity of methanolic extracts of Operculina turpethum leaves (MEOTL), stem (MEOTS), and roots (MEOTR) in vitro methods. The antioxidant activity was evaluated by reducing power, 2, 2- diphenyl-1-picrylhydrazyl radical (DPPH) photometric assay, nitric oxide free radical scavenging, iron chelation, hydrogen peroxide (H₂O₂) scavenging activities. The total phenolic content was determined by the Folin-Ciocalteu method. The percent reduction and IC₅₀values were calculated using standard methods. The MEOTS and MEOTR exhibited scavenging activity lower than gallic acid at similar concentrations in Folin-Ciocalteu method. The IC₅₀ values of the ascorbic acid, MEOTL, MEOTS, and MEOTR were found to be 46.67 ± 1.67, 50.01 ± 2.13, 72.63 ± 2.76 and 85.0 ± 3.55 µg, respectively in DPPH assay. The IC₅₀values of the ascorbic acid, MEOTL, MEOTS, and MEOTR were found to be 14.32 ± 1.45, 18.15 ± 2.23, 20.80 ± 1.88  and 23.71 ± 2.67 µg, respectively in reducing power method. Among all extracts, MEOTS has higher antioxidant activity. Further   investigations are needed to identify the lead molecule and to elucidate the structure and exact   mechanism of action for their antioxidant activity.

Key words: Antioxidant, diabetes, 2, 2- diphenyl-1-picrylhydrazyl, Operculina turpethum,reactive oxygen species.