In order to investigate the inhibitory effect of a novel bioactive peptide, Tyr-Pro-Ile-Trp (YPIW), on α-glucosidase, a variety of analytical methods including enzyme inhibition kinetics, ultraviolet (UV) absorption spectroscopy and Fourier transform infrared spectroscopy (FTIR) were employed to investigate the underlying inhibitory mechanism. Besides, the stability and cytotoxicity of YPIW were evaluated. The results indicated that YPIW exerted a significant inhibitory effect on α-glucosidase (half maximal inhibitory concentration (IC₅₀) = 1.03 mmol/L), which was comparable to that of acarbose (IC₅₀ = 1.08 mmol/L). In the mixed competition mode, YPIW could reversibly inhibit the activity of α-glucosidase, and was more likely to bind with free α-glucosidase. The UV and FTIR showed that YPIW interacted with α-glucosidase, potentially altering the conformation of the enzyme, thereby reducing its catalytic activity. YPIW remained stable at low temperatures or in acidic environments, and had good tolerance to simulated gastrointestinal digestion. In addition, it had no obvious toxic effect on HepG2 cells in the concentration range of 0–1 mmol/L. This study provides a theoretical basis for the development of YPIW as a novel hypoglycemic peptide.

In order to investigate the interaction between aloe emodin and α-glucosidase, enzyme kinetics, ultraviolet (UV) spectroscopy, infrared (IR) spectroscopy and fluorescence spectroscopy were employed to investigate the inhibitory mechanism of aloe emodin on α-glucosidase and the synergistic effect of aloe emodin in combination with acarbose was also investigated in this study. The results showed that aloe emodin had better inhibitory effect on α-glucosidase as both a noncompetitive and anti-competitive inhibitor when compared with acarbose. The results of UV spectroscopy indicated that a new complex was formed through the interaction between aloe emodin and α-glucosidase. The characteristic vibrations of amide groups in the IR spectra indicated that the structural conformation of α-glucosidase changed with the addition of aloe emodin. The results of fluorescence quenching experiments showed that the endogenous fluorescence of α-glucosidase was statically quenched by aloe emodin. In addition, it was also found that aloe emodin combined with acarbose had a synergistic inhibitory effect on α-glucosidase activity. This study provides an experimental basis for the future application of aloe emodin in health foods for regulating blood glucose.