The complex formed by naringenin and α-amylase resulted in the decreased antioxidant activity of naringenin and catalytic activity of enzyme, as well as efficient quenching of the intrinsic fluorescence of α-amylase. The inhibitory effect of naringenin on α-amylase was studied by enzymatic kinetics and fluorescence spectroscopy. α-Amylase (0.33 U/mL, 0.2 mL) was treated by naringenin (1 mg/mL, 0.05 mL) under pH 6.8, 37 ℃ for 20 min, the inhibition rate reached 36.6 %. The mechanism of inhibition effect was noncompetitive inhibition. The regular quenching of intrinsic fluorescence of α-amylase was induced by naringenin as a quencher in physiological condition, and the majority was static quenching. Naringenin binded with α-amylase to form a new complex was using hydrophobic interaction. An α-amylase molecule provided one binding site for a naringenin molecule, with the apparent binding constant Kb around 105 L?mol-1. The total antioxidant activity in linoleic acid emulsion and reducing power of naringenin were also inhibited by α-amylase, which might lead to the change of biological activity of naringenin.
