Free radical scavenging activity of the extracts was measured using a stable 2,2-diphenyl-2-picrylhydrazyl radical (DPPH) as described by Hartwig, Brumovsky, Fretes, and Boado (2012). In brief, to induce the reaction, a 3 ml working solution [a mixture of the DPPH stock solution (4 mg DPPH and 100 ml EtOH) and EtOH, with an initial absorbance of 1.2 0.02.] was added to a 100 ml sample extract (adequately diluted with EtOH). This mixture was vigorously shaken, and was stored at room temperature in the dark for 1.5 h. The decrease in absorbance at 517 nm was recorded using ethanol as the blank by a spectrophotometer (Model Spectronic Genesys 10 UV Scanning Thermo Electron Corporation, U.S.A.). A reduction in absorbance indicates an increased power of free radical scavenging ability. Each essay was carried out in triplicate. Ascorbic acid was used as a reference material. A standard curve of ascorbic acid
(R2 ¼ 0.9915) was prepared and results were reported as mg of
ascorbic acid equivalent (AAE) per 1 g of sample weight (on dry basis).