Understanding phenolic acids inhibition of α-amylase and α-glucosidase and influence of reaction conditions

Phenolic acids are involved in modulating the activity of starch digestive enzymes but remains unclear if their interaction with enzymes or starch is governing the inhibition. The potential inhibition of nine phenolic acids against α-amylase and α-glucosidase was studied applying different methodologies to understand interactions between phenolic acids and either enzymes or substrates. Vanillic and syringic acids were prone to interact with α-amylase requiring low half-maximum inhibitory concentration (IC50) to inhibit starch hydrolysis. Nevertheless, the initial interaction of phenolic acids with starch somewhat obstructed their interaction with starch, requiring 10 times higher IC50, with the exception of chlorogenic and gallic acid. The study demonstrates that 10% of the phenolic acids were retained during starch gelatinization. Those effects were not really evident with α-glucosidase, likely due to the small molecular size of maltose substrate. Phenolic acids with > 1 hydroxyl group like caffeic and protocatechuic acids showed the lowest IC50 against α-glucosidase.