Inhibitory kinetics and mechanism of flavonoids from lotus (Nelumbo nucifera Gaertn.) leaf against pancreatic alpha-amylase

In this study, lotus leaf flavonoids (LLF) were found to show a notable inhibition activity on alpha-amylase in a mixed-type manner with IC50 value of (5.58 +/- 0.10) mg/mL. The intrinsic fluorescence of alpha-amylase was quenched by the interaction with LLF through a static quenching mechanism, and LLF-alpha-amylase complex was spontaneously formed mainly driven by the hydrophobic interaction and hydrogen bonding. Multispectroscopic analyses (synchronous fluorescence, three-dimensional fluorescence, circular dichroism (CD) and fourier transform infrared spectra (FT-IR)) comprehensively demonstrated that the binding of LLF to alpha-amylase would change the conformation and microenvironment of alpha-amylase, resulting in inhibiting the enzyme activity. The present study indicated that LLF had potential to be as an ingredient in functional food for the prevention of type-2 diabetes. (C) 2018 Elsevier B.V. All rights reserved.