Anthocyanin profile and antioxidant activity from 24 grape varieties cultivated in two Portuguese wine regions

Aims: The purpose of this work was to evaluate the general phenolic composition and the anthocyanin profile of 24 grape varieties from two Portuguese wine regions as well as their antioxidant activity in the different grape berry fractions (skins, pulps and seeds). Methods and results: Individual anthocyanin composition of grape skin extracts was analyzed by HPLC, whereas total antioxidant activity was evaluated by two methods: DPPH and ABTS. In general, a high variability was found among the different autochthonous and non-autochthonous grape varieties in relation to the polyphenolic compounds analyzed, especially the individual anthocyanins. The individual anthocyanins in grape skin extracts were mainly malvidin (1.40-7.09 mg/g of skin), in particular malvidin-3-glucoside (0.62-6.09 mg/g of skin). The highest antioxidant activity was consistently detected in the seed extracts; however, it was not possible to establish a clear difference among the grape varieties analyzed. Conclusion: High variability in polyphenolic content, individual anthocyanin composition and antioxidant activity was found among the diverse autochthonous and non-autochthonous grape varieties studied. Seeds showed the highest antioxidant activity, followed by skin and pulp, irrespective of the grape variety. Significance and impact of the study: Most vineyards in Portugal grow Portuguese cultivars of Vitis Vinifera L. and other cultivars grown worldwide. The phenolic compounds and antioxidant activity of these grape cultivars have never been characterized under the environmental conditions of the Douro and Dão regions. The variability in phenolic content among the grape varieties studied confirms the hypothesis that genetic factors have an important role in the biosynthesis of these compounds and, consequently, in the antioxidant activity of grapes.