Structure-effect relationship of phenolic compounds on α-amylase inhibition studied by isothermal titration calorimetry

Recent studies have emphasized the therapeutic potential of polyphenols in regulating blood glucose levels. To assess the inhibitory effects of different phenolic structures and various plant extracts on pancreatic <i>α</i>-amylase in real-time under physiologically relevant conditions, starch hydrolysis was monitored by isothermal titration calorimetry. Significant impact of the phenolic structure was observed for the inhibition strength and mechanism. While some polyphenols demonstrated reversible inhibition, others seem to form aggregates. Traditional apple varieties exhibited greater <i>α</i>-amylase inhibition than commercial varieties. Apple peel, characterized by higher phenolic contents and flavonols, exceeded the inhibition by extracts from flesh. Aronia rich in procyanidins and tea with EGCG revealed excellent and concentration-dependent inhibition. In contrast to cyanidin-3-<i>O</i>-glucoside, black carrot anthocyanins exhibited insignificant inhibition, indicating a limiting impact of the sugar acylation. These findings underscore the role of specific polyphenol structures in modulating carbohydrate digestion, suggesting their potential for managing glycaemic control.