Inhibitory Effect of Monascus Fermented Products on Non-Enzymatic Glycation of Proteins

The advanced glycation end products (AGEs) are formed during the non-enzymatic glycation of proteins. Studies have shown that the accumulation of AGEs is closely related to the occurrence and development of diabetes as well as its complications. To investigate the effects of Monascus fermented products (MFP) on protein glycosylation products and their structures, an in vitro simulation system of bovine serum albumin-fructose was constructed. The results demonstrated that MFP exerted an inhibitory effect on the generation of early, intermediate, and end-stage products of protein glycosylation, particularly on the end-stage products, namely AGEs, with the highest inhibition rate (87.80%). As the mass concentration of MFP increased from 0.05 mg/mL to 0.55 mg/mL, the carbonyl content of glycosylated proteins decreased from 32.50 μmol/g to 28.10 μmol/g, while the content of free sulfhydryl increased from 2.60 μmol/g to 3.50 μmol/g. Meanwhile, the detected maximum inhibition rates of protein oxidation products, namely dityrosine and kynurenine, were 66.84% and 59.37%, respectively. These findings suggested that MFP could exert AGEs inhibition by protecting sulfhydryl groups and inhibiting protein oxidation. The contents of α-helical structures in glycosylated proteins were found to be reduced in comparison to those observed in native proteins. However, the addition of MFP resulted in an increase in the contents of α-helical structures. This indicated that MFP might inhibit the generation of AGEs through stabilizing the natural conformation of the protein. The content of amyloid β-crosslinked structures in glycosylated proteins was relatively high, and its content was significantly reduced by the addition of MFP, and with the increase of MFP addition amount, the inhibition rate of amyloid β-crosslinked structure formation gradually increased, demonstrating that MFP could effectively inhibit protein cross-linking and thus block the formation of AGEs. This study provided data support and theoretical basis for the development and utilization of AGEs inhibitors derived from Monascus.