Brown sugar polyphenols as natural inhibitors of α‐amylase and α‐glucosidase enzymes

Summary This study investigated the compositional profile and inhibitory effect of brown sugar polyphenols (BSPs) on porcine pancreatic α‐amylase (PPA) and Baker's yeast α‐glucosidase (BYG) activities. The HPLC‐ESI‐MS (high‐performance liquid chromatography‐electrospray ionisation‐mass spectrometry) analysis showed that BSPs comprised of four hydroxybenzoic acids including protocatechuic, p‐hydroxybenzoic, vanillic and syringic acids (PA, PHBA, VA and SA, respectively) and three hydroxycinnamic acids including chlorogenic, p‐coumaric and ferulic acids (CHA, PCA and FA, respectively), where CHA (29.24%) and SA (31.31%) were the main BSPs. The enzyme inhibition analysis expressed as IC50 values (except PA and VA) showed that CHA, PCA and FA exhibited higher PPA and BYG inhibitory activities than PHBA and SA, following the order of CHA > PCA > FA > PHBA > SA. Moreover, the BSPs showed better inhibitory activities against BYG than PPA. The inhibition mechanism analysis through inhibitory kinetics, fluorescence quenching, differential scanning calorimetry and molecular docking demonstrated that the BSPs inhibited the enzymes by binding with them mainly via hydrogen bonds. The results suggested that BSPs could be natural inhibitors of PPA and BYG. Brown sugar polyphenols are comprised of four hydroxybenzoic acids, including protocatechuic acid (PA), p‐hydroxybenzoic acid (PHBA), vanillic acid (VA) and syringic acid (SA), as well as three hydroxycinnamic acids, including chlorogenic acid (CHA), p‐coumaric acid (PCA) and ferulic acid (FA). These compounds exhibit inhibitory activities on α‐amylase and α‐glucosidase enzymes.