Effects of plant extract aurantio-obtusin on pepsin structure: Spectroscopic characterization and docking simulation

Semen cassiae tea is a functional beverage, which is commonly drunk as a kind of roasted tea in Korea and China. This study was performed to characterize the binding mechanism of aurantio-obtusin, a major bio-activity compound of semen cassiae tea, with pepsin by experimental and theoretical methods. Steady-state and time-resolved fluorescence experiments showed that binding of aurantio-obtusin with pepsin occurred through static quenching mechanism. The binding mode was displayed using molecular simulation, which suggested that the binding process was spontaneous and might involved hydrophobic and hydrogen bonding forces. Three-dimensional fluorescence, FTIR, and Circular dichroism data further confirmed the secondary structure changes in pepsin upon aurantio-obtusin. This study may provide theoretical basis for its application in pharmaceutics and clinic. (C) 2017 Elsevier B.V. All rights reserved.