Inhibition of α-amylase activity by condensed tannins

The ability of grape seed procyanidins to inhibit α-amylase activity was studied using a colorimetric method. This ability was found to be related with the average degree of polymerisation of the tested procyanidins. These interactions were further evaluated by fluorescence quenching, dynamic light scattering (DLS) and nephelometry, in order to understand the mechanisms by which they occur. A relationship between aggregate formation and enzymatic inhibition was observed. The interaction between procyanidins and enzyme involves a specific interaction as inferred from the calculated apparent bimolecular quenching constant in the fluorescence assays. Further experiments involved the determination of the effect of carbohydrates on the enzymatic inhibition observed. It was shown that pectin and arabic gum inhibited the formation of insoluble aggregates but were unable to restore fluorescence and activity to the enzyme. This suggests that these carbohydrates resulted in a decrease in turbidity due to the formation of a ternary complex with protein/polyphenol.