The inhibitory effects of free and bound phenolics from Phyllanthus emblica Linn. on α‐amylase: a comparison study

Abstract BACKGROUND Phyllanthus emblica Linn. (PE) is rich in polyphenols, which can be categorized into free and bound phenolics (PEFP and PEBP). This study evaluated the inhibitory effect of PEFB and PEBP on α ‐amylase for the first time. The mechanism of the inhibition effect of PEFP and PEBP on α ‐amylase was investigated by enzyme inhibition kinetics, multispectral analysis, thermodynamics, and molecular docking. RESULTS Free and bound phenolics inhibited α ‐amylase activity effectively in a mixed type of inhibition. Fluorescence quenching and thermodynamic analyses showed that the binding of PEFP and PEBP to α ‐amylase occurred through a static quenching process ( K q = 6.94 × 10¹² and 5.74 × 10¹² L mol −1 s −1 ), which was accompanied by a redshift ( λ em from 343 to 347 nm), leading to a change in the microenvironment. This process was found to be a spontaneous exothermic reaction (ΔG < 0). Circular dichroism (CD) analysis confirms that the secondary structure of α ‐amylase was altered, in particular a decrease in α ‐helixes and an increase in random coils. Molecular docking studies showed that PEFP and PEBP interacted with α ‐amylase through hydrogen bonding and hydrophobic interactions. CONCLUSION The present study provides valuable insights into the mechanism of action of PEFP and PEBP on α ‐amylase, which will provide a theoretical basis for their possible use as novel natural α ‐amylase inhibitors. © 2024 Society of Chemical Industry.