In vitro evaluation of the anti-diabetic potential of soymilk yogurt and identification of inhibitory compounds on the formation of advanced glycation end-products

In this study, we aimed to identify starter strains of lactic acid bacteria (LAB) to produce soymilk yogurt that can decrease the risk of diabetes mellitus (DM) and its complications. The inhibition assays of the dipeptidyl peptidase IV (DPP- IV) and advanced glycation end products (AGEs) formation were conducted using 70% ethanol (EtOH) extraction of freeze-dried soymilk yogurt. Soymilk yogurt produced using Weissella confusa TOKAI 2 showed the highest inhibition rate in the α-amylase inhibition assay, while soymilk yogurt produced using Lactiplantibacillus plantarum TOKAI 17 showed the highest inhibition rates in the α-glucosidase and DPP-Ⅳ inhibition assays, respectively. Soymilk yogurt produced using Streptococcus macedonicus TOKAI 4 showed the highest inhibitory activities in Nω-(carboxymethyl) arginine (CMA) and Nε-(carboxymethyl) lysine (CML) formation, respectively. Furthermore, soymilk yogurt prepared using Lb. plantarum TOKAI 17 and Lactiplantibacillus pentosus TOKAI 35 exhibited higher proportions of aglycone isoflavones than soymilk and showed a higher fluorescent AGEs inhibitory activity than that of soymilk (p < 0.05). Interestingly, the inhibition assay assessing fluorescent AGEs formation using isoflavones indicated that aglycone-type isoflavones, such as genistein and daidzein, had higher inhibitory activities than that of glycosides (p < 0.05). These results indicate that soymilk yogurt produced using Lb. plantarum TOKAI 17 and Lb. pentosus TOKAI 35 had inhibitory effects on α-glucosidase, DPP-Ⅳ, and AGEs formation in vitro, and that aglycone isoflavones might inhibit the formation of fluorescent AGEs.