Phenolic contents and antioxidant activities in ethanol extracts of Citrus reticulata Blanco cv. Ougan fruit

The phenolic contents in ethanol extracts of Citrus reticulata Blanco cv. Ougan fruit grown in seven regions of Zhejiang Province, PR. China, were measured. The antioxidant activities of extracts were also evaluated. The total phenolic acid (TPA) content in the pulp of fruit ranged from 10.535 to 15.535 mg gallic acid equivalents (GAE)/g and the total flavonoids (TF) content varied from 1.683 to 2.525 mg rutin equivalents (RE)/g. In the peel of fruit, the TPA content ranged from 15.595 to 18.950 mg GAE/g and the TF content from 4.671 to 5.796 mg RE/g. Among all of the ethanol extracts analyzed, the Sanyang sample exhibited a significantly higher TPA content in pulp of fruit than other samples (P<0.05), while in the peel of fruit, the Jiukeng sample showed a higher TPA content than other samples (P<0.05). The antioxidant activities were evaluated by in vitro experiments using reducing power, scavenging assays of DPPH radicals, ABTS(+) radicals and ferric reducing antioxidant power (FRAP), respectively. Compared with the antioxidant activity in the ethanol extracts of the pulp of cv. Ougan from seven regions, the Sanyang sample had the strongest antioxidant activities in scavenging DPPH radicals and ABTS(+) radicals, while in the pulp of the Jiukeng sample showed the best performance in reducing power, scavenging assays of DPPH radicals, ABTS(+) radicals and ferric reducing antioxidant power. The extremely significant correlation (P<0.01) existed between the TF content and ABTS(+) radical scavenging activity, and a significant correlation was found between the former and DPPH radical scavenging activity, but no significant correlation was found between the former and the total reducing activity. Meanwhile, the correlations between the TPA content and DPPH radical, ABTS(+) radical scavenging activity and ferric reducing antioxidant power were significant (P<0.05), but no significant correlation was observed between the former and total antioxidant activity in the peel of cv. Ougan. Ethanol extracts of fruits from some selected regions exhibited stronger antioxidant activities compared to those of the commercial compound (Trolox). It might be considered as a potential plant source of antioxidants.