This study examined the antioxidant capacities of apple peel, grape peel, and sweet potato peel. The antioxidant activities were evaluated using total phenolic contents, total flavonoids contents, DPPH radical scavenging activity, ABTS radical cation scavenging activity, FRAP reducing power, and ORAC assay. The total phenolic (7.76 μM quercetin equivalent/g peel) and total flavonoids (1.03 μM quercetin equivalent/g peel) contents in apple peel were significantly higher than in grape peel and sweet potato peel (P<0.05). The scavenging activities of DPPH and ABTS radicals of a 70% ethanol extract of apple peel was 3.2-4.6 and 2.8-5.4 times high than those of grape and sweet potato peel, respectively. In addition, the FRAP reducing power and ORAC assay of 70% ethanol extraction from apple peel were significantly higher than those of the other samples. Therefore, apple peel can be used efficiently as a natural antioxidant.
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