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چکیده
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This study has aimed to determine the amount of flavonoids, anthocyanins, total phenolic compounds, ascorbic acid and antioxidant activity of the grape in the polar and nonpolar sub-fractions of methanolic extracts with two extraction methods, maceration and ultrasonic. The phenolic compounds content and antioxidant activity of selected grape (Vitis vinifera L. "Red Seedless") from Maragheh region, East Azerbaijan (Iran) were investigated with a view to their exploitation as a potential source of natural antioxidants. Antioxidant activities of the samples were determined by three testing systems namely DPPH, βcarotene/linoleic acid and reducing power assays. In the DPPH system, the highest radical scavenging activity was observed by the polar sub-fraction of the methanolic extract in frozen fruits (IC50 = 26.34 ± 6.5 µg/ml). In order to evaluate the efficiency of different methods for the extraction of the main polyphenols in grape, two methods were tested and compared. The results showed that the maceration method is better method as compared to the ultrasonic method. These advantages are visible on extracting of the flavonoids, anthocyanin, total phenolic, ascorbic acid contents and antioxidant capacity. Our findings demonstrate that the methanolic extracts of frozen and dried fruits of Vitis vinifera may be suggested as a strong potential source of natural antioxidant.
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