Diversity of physicochemical profiles of grape (Vitis vinifera L.) and their antioxidant properties

Grapes (Vitis vinifera L.) are known for their deliciousness and health benefits. In the present study, the variations of physicochemical profiles and antioxidant activities of 25 grape varieties were evaluated. Among the varieties tested, glucose and fructose were the main sugars, and tartaric and malic acids were the main organic acids in all grapes. Shine Muscat was characterized as suitable for fresh eating due to its high sugar contents and low acid contents. While JintianMeigui had high sugar and anthocyanins contents, making it suitable for cultivation. Results showed that all grape fractions are sources of phenolic compounds and varied among cultivars. In general, regardless of cultivars, seed extracts showed the highest content of total phenolics and total proanthocyanidins contents, consistent with the observed higher antioxidant activities. Combining high-performance liquid chromatography (HPLC) and high-resolution tandem mass spectrometry (HRMS) technologies, a total of 28 phenolic components were preliminarily identified. The most abundant anthocyanins in skins were petunidin-3-glucoside and malvidin-3-glucoside, as well as catechin and epicatechin were the principal proanthocyanidins in seeds. Pearson correlation coefficient analysis showed the significant linear correlations between proanthocyanidins (catechin, epicatechin, proanthocyanidin A1, proanthocyanidin B1, proanthocyanidin B2, proanthocyanidin C1 and epicatechin-3-O-gallate) and antioxidant activities. However, further studies are needed to demonstrate and elucidate the health benefits of grapes for human nutrition as antioxidants. Overall, our results provided theoretical guidance for the further development and utilization of grapes.