Assessing the anthocyanic composition of Port wines and musts and their free radical scavenging capacity

The anthocyanic composition of must and different types of Port wine (Ruby, LBV and Tawny from nine producers) was evaluated by HPLC. In addition, the radical scavenging activity of these Port wines was evaluated by using DPPH radical microassay. Musts, Ruby and LBV Port wines presented similar qualitative profiles of anthocyanins and quantitative differences, ranging from 382-601, 92-156 and 32-78 mg of malvidin-3-O-glucoside equivalent/l, respectively. Anthocyanins in Tawny Port wines ranged between not detected and 51 mg of malvidin-3-O-glucoside equivalent/l. Principal component analysis was applied to the percentage (in weight) of each compound in relation with the total content of anthocyanins. PCA yielded two components explaining 90.9% of the total variance. The first PC correlates positively with the glucoside derivatives of delphinidin, cyanidin, petunidin and malvidin. The second PC correlates positively with pyruvic acid adducts of anthocyanins that resulted from vinification process. Ruby and LBV presented low amounts of glucoside derivatives and variable amounts of pyruvic acid adducts of anthocyanins. Acid hydrolysis allowed the identification of five anthocyanidins. Malvidin was the most abundant one. LBV Port wine showed the strongest antiradical activity, while Tawny Port wines revealed the lowest ones, with these wines presenting lower amounts of anthocyanic compounds owing to their “oxidative” aging in wooden barrels. These results suggest that aging process is an important factor influencing the antioxidant activity of Port wines.