Mechanistic Approach by Which Polysaccharides Inhibit α-Amylase/Procyanidin Aggregation

The present work studies the inhibition of aggregation of alpha-amylase and procyanidin fractions by different polysaccharides (arabic gum, beta-cyclodextrin, and pectins). Several analytical approaches, namely, fluorescence quenching, nephelometry, and dynamic light scattering (DLS), were used. In general, nephelometry showed that the presence of the polysaccharides in solution reduced the formation of insoluble aggregates. The fluorescence quenching measurements showed two effects: arabic gum and beta-cyclodextrin reduce the quenching effect of procyanidin fractions on a-amylase fluorescence, whereas pectins do not affect the quenching of alpha-amylase fluorescence by procyanidin fractions. DLS measurements have revealed that the polysaccharides studied induce a decrease in aggregates size, which probably is due to the formation of smaller aggregates resulting from the disruption and reorganization of the procyanidin fractions/alpha-amylase aggregates. Overall, the results obtained for arabic gum and beta-cyclodextrin strongly suggest that the main mechanism by which these two compounds inhibit protein/polyphenol aggregation is by molecular association between these polysaccharides and polyphenols, competing with protein aggregation. In the case of pectins, the results obtained provide evidence that the main mechanism by which they reduce protein/polyphenol aggregation is by forming a protein/polyphenol/polysaccharide complex, enhancing its solubility in aqueous medium.