In the present study, we carried out a systematic research on relative antioxidant activity of aqueous leaf extract of Stevia rebaudiana. The DPPH activity of aqueous leaf extract (20, 40, 50, 100 and 200 μg/ml) was increased in a dose dependent manner, which was found in the range of 40.00-72.37% as compared to ascorbic acid 64.26-82.58%. The IC(50) values of aqueous extract and ascorbic acid in DPPH radical scavenging assay were obtained to be 83.45 and 26.75 μg/ml, respectively. Measurement of total phenolic content of the aqueous leaf extract of S. rebaudiana was achieved using Folin-Ciocalteau reagent containing 56.73 mg/g of phenolic content, which was found significantly potent when compared to reference standard gallic acid. The aqueous extract also inhibited the hydroxyl radical, nitric oxide and superoxide anions with IC(50) values of 100.86, 98.73 and 100.86 μg/ml, respectively. The greater amount of phenolic compounds leads to more potent radical scavenging effects as shown by the aqueous leaf extract of S. rebaudiana.
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