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Phenolic acids are widely found in fruits and vegetables. The inhibitory effect of phenolic acids on α-amylase, a key enzyme for starch digestion, has attracted the attention of researchers. To further investigate the effects of different substituents on the benzene ring of phenolic acid on the inhibition of α-amylase activity, in vitro experiments and molecular docking were used. The structure-activity relationships of 17 phenolic acids with benzoic acid as the parent nucleus were analyzed by determining their half inhibitory concentration (IC50) toward α-amylase. The results showed that 2,3,4-trihydroxybenzoic acid had the strongest inhibitory effect on α-amylase with an IC50 value of 17.30 ± 0.73 mM. According to the structure-activity analysis, the hydroxyl group at the 2-position on the benzene ring had a strong positive effect on the inhibitory activity of α-amylase, while methoxylation at the 2-position and hydroxylation at the 5-position had a negative effect. Molecular docking revealed that hydrogen bonding and hydrophobic interactions were involved in the inhibition, with hydrogen bonding being the primary force. These findings provide a more comprehensive understanding of phenolic acids as inhibitors of α-amylase and provide new ideas for the design of dietary formulations for diabetic patients. [ABSTRACT FROM AUTHOR]

In this study, the structure-activity relationship and interaction mechanism of nine flavonoids and porcine pancreatic α-amylase were studied through enzyme kinetics, multispectral analysis and molecular simulation. The analysis of the structure-activity relationship illustrated that hydroxylation at C4′ and C5′ position of flavonoids increased the inhibitory activity against α-amylase while the methylation at the corresponding position decreased it. According to the fluorescence quenching assay, all flavonoids could efficiently quench the intrinsic fluorescence of amylase by static mechanism and the thermodynamic parameters of representative Luteolin and Quercetin indicated the key role of hydrogen bonds and van der Waals interactions. The multispectral study suggested that the binding of flavonoids alters the secondary structure of α-amylase, leading to significant inhibition. Moreover, these findings were further confirmed by molecular docking which demonstrating the importance of hydrogen bonding and hydrophobic forces in flavonoid and porcine pancreatic α-amylase interactions.

The inhibitory mechanism of chlorogenic acid (CHA) against porcine pancreatic α-amylase (PPA) was examined by enzyme kinetic analysis, circular dichroism, fluorescence quenching and molecular docking. As a result, CHA showed a mixed-type inhibitory action on PPA, with the IC50 value of 0.498 ± 0.013 mg/mL. Analysis of fluorescence and circular dichroism spectra confirmed that CHA altered the secondary structure of PPA, by interacting with the amino acid residues around or distant from the catalytic site of PPA, mainly through hydrogen bonds, and this interaction was closely associated with the enzyme’s activity. Molecular docking indicated that the best pose between CHA and PPA was achieved with the binding energy of −7.8 and −7.2 kcal/mol at the active site and inactive site of PPA, respectively. The performed study reveals that CHA has the potential to inhibit the activity of α-amylase, thereby representing a novel idea to delay the digestion of starch.

The starch from waxy/amylose extender (wx/ae) double-mutant rice is almost indigestible by porcine pancreatic α-amylase (PPA) and behaves like resistant starch, even though PPA digests waxy mutant (wx) and wild-type (WT) rice starches easily. To clarify the relationship between binding ability and susceptibility to PPA hydrolysis, we studied the PPA adsorption capacity of wx/ae starch. Results showed that the wx/ae starch adsorbed 80% more PPA than wx and WT starches, consistent with the ratio of their specific surface areas. This suggests that PPA adsorption capacity is determined by the specific surface area of starch granules. Thus, the resistance to digestion of the wx/ ae starch is not due to adsorption capacity, but to the higher-order nanostructure of the starch granules. The morphological features of digested wx/ae starch granules observed by scanning electron microscopy (SEM) suggest that the higher-order nanostructure of wx/ae starch is similar to that of resistant starches, such as high-amylose rice and potato starches. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydroxylation and methoxylation of flavonoids greatly influence the inhibition on PPA. • The structure of Luteolin exhibits potent inhibitory effect. • Hydrophobic interaction and hydrogen bonds are essential for the interaction. • Flavonoids could alter the secondary structure of PPA. In this study, the structure-activity relationship and interaction mechanism of nine flavonoids and porcine pancreatic α-amylase were studied through enzyme kinetics, multispectral analysis and molecular simulation. The analysis of the structure-activity relationship illustrated that hydroxylation at C4′ and C5′ position of flavonoids increased the inhibitory activity against α-amylase while the methylation at the corresponding position decreased it. According to the fluorescence quenching assay, all flavonoids could efficiently quench the intrinsic fluorescence of amylase by static mechanism and the thermodynamic parameters of representative Luteolin and Quercetin indicated the key role of hydrogen bonds and van der Waals interactions. The multispectral study suggested that the binding of flavonoids alters the secondary structure of α-amylase, leading to significant inhibition. Moreover, these findings were further confirmed by molecular docking which demonstrating the importance of hydrogen bonding and hydrophobic forces in flavonoid and porcine pancreatic α-amylase interactions. [ABSTRACT FROM AUTHOR]

• Chlorogenic acid showed a mixed-type inhibitory action on α-amylase. • Chlorogenic acid altered the secondary structure of α-amylase through hydrogen bonds. • Chlorogenic acid interacted with α-amylase active site or far from its catalytic site. • Chlorogenic acid is a potential inhibitor of α-amylase. The inhibitory mechanism of chlorogenic acid (CHA) against porcine pancreatic α-amylase (PPA) was examined by enzyme kinetic analysis, circular dichroism, fluorescence quenching and molecular docking. As a result, CHA showed a mixed-type inhibitory action on PPA, with the IC 50 value of 0.498 ± 0.013 mg/mL. Analysis of fluorescence and circular dichroism spectra confirmed that CHA altered the secondary structure of PPA, by interacting with the amino acid residues around or distant from the catalytic site of PPA, mainly through hydrogen bonds, and this interaction was closely associated with the enzyme's activity. Molecular docking indicated that the best pose between CHA and PPA was achieved with the binding energy of −7.8 and −7.2 kcal/mol at the active site and inactive site of PPA, respectively. The performed study reveals that CHA has the potential to inhibit the activity of α-amylase, thereby representing a novel idea to delay the digestion of starch. [ABSTRACT FROM AUTHOR]