Comparison of phenolic profiles and antioxidant activities in skins and pulps of eleven grape cultivars (Vitis vinifera L.)

Eleven grape cultivars were analysed to explore the variety differences of fresh grape phenolic profiles. The results showed that free phenolics were predominant in grape skins and pulps, and showed the higher antioxidant activities than bound. In 11 cultivars, Muscat Kyoho extracts had the highest total phenolic content in skins (10.525 mg GAE g−1 FW) and pulps (1.134 mg GAE g−1 FW), and exhibited the highest DPPH radical scavening capacity (EC50=11.7 μg mL−1) and oxygen radical absorbance capacity (ORAC) value (190.57 μmol TE g−1 FW) of free phenolic in skin. In addition, the most abundant phenolics in grape skins were found to be flavonoids such as kaempferol in Kyoho skin (541.2 μg g−1 FW), rutin, catechin and epicatechin in Muscat Kyoho skin (262.3, 86.3 and 70.0 μg g−1 FW, respectively). Furthermore, the principal component analysis showed a strong difference of phenolic profiles with the cultivars, existing forms and distributions. Pearson correlation coefficient analysis showed a significant linear correlation between total phenolic content and antioxidant activity (P<0.05). Therefore, both skins and pulps were rich sources of bioactive phenolic compounds, and Muscat Kyoho was the ideal source among all samples.