Comparative Study of Some Physicochemical and in vitro Biological Properties of Juices of Four Pomegranate Cultivars

The pomegranate (Punica granatum L.) juice, peels, and kernels are rich in secondary metabolites responsible for some biological properties that are important in healthy eating. Among them, anthocyanins present in the arils and, therefore, in juices are pigments with antioxidant and anti-inflammatory activities. In the Algarve region (southern Portugal), a century old variety Assaria is largely cultivated, but there is lack of information about its chemical and biological characteristics. In the present work, a comparative study of the pomegranate juice was made, over three years (2017-2019), between this cultivar and three other well-known cultivars (Wonderful, Mollar de Elche, and Acco). The variables studied were pH, titratable acidity, formol number, total phenol content, total monomeric anthocyanins, and polymeric color. The in vitro biological activities of pomegranate juices studied were antioxidant through the capacity for scavenging ABTS and NO free radicals; and inhibitory activities on lipoxygenase and alpha-glucosidase activities. Simultaneously, the biological activities of the main anthocyanins of pomegranate juice were also determined and compared with the juice samples. The results showed that Assaria had characteristics similar to Mollar de Elche, with lower amounts of total phenols (2.609 and 2.849 mg mL(-1), respectively) and monomeric anthocyanins (104.785 and 82.047 mg L-1, respectively) and lower antioxidant and anti-inflammatory activities than the other two cultivars. Wonderful had the highest amounts of those metabolites (7.072 and 594.944 mg L-1, respectively) and the best activities. 'The in vitro biological activities of individual anthocyanins were significantly higher than the juices. The juice activities of Wonderful cultivar were the closest to anthocyanin ones. The best activities of isolated anthocyanins lead to the hypothesis that those antagonistic effects can occur among the juices' constituents and decrease their activities.