Variation of Polyphenols, Anthocyanins and Antioxidant Power in the Strawberry Grape (Vitis labrusca) after Simulated Gastro-Intestinal Transit and Evaluation of in Vitro Antimicrobial Activity

The influence of a simulated digestive process on some biochemical and biological aspects of strawberry grape (Vitis labrusca) was investigated. The amount of total polyphenols and anthocyanins as well as the antioxidant power were evaluated. Results evidenced that the simulated gastrointestinal transit caused a decrease of the polyphenols content and total anthocyanins; these last, however, were more resistant than polyphenols, decreasing only of 50% respect to the initial value (31.50 μg/ml of extract). The extract exhibited an excellent antioxidant power (EC50 3.8 mg/ml), which decreased of about four times after the simulated gastrointestinal transit. The antimicrobial activity of the extract, evaluated against three Escherichia coli, Pseudomonas aeruginosa and Bacillus cereus pathogen strains was enhanced by the simulated digestion, with an increase of the inhibition halo.