ACE inhibitory activity and bioconversion of isoflavones by Lactobacillus in soymilk supplemented with B-vitamins

Purpose - The aim of this study is to examine the bioactive properties of lactobacilli-fermented B-vitamin soymilk, namely the in-vitro antihypertensive property and bioconversion of isoflavone glucosides to aglycones. Design/methodology/approach - Lactobacillus acidophilus BT 1088, L. fermentum BT 8219, L acidophilus FTDC 8633 and L. gasseri FTDC 8131 were investigated for their bioactive potential and enhanced bioconversion of isoflavones in soymilk supplemented with individual B-vitamins at a concentration of 1 mg/L. Findings - The supplementation of thiamine, riboflavin, niacinamide, calcium pantothenate, biotin and folic acid enhanced the ACE-inhibitory activity of lactobacilli in soymilk accompanied by a lower IC50 value compared to the control (P < 0.05). The beta-glucosidase specific activity of lactobacilli was also enhanced on supplementation of B-vitamins, leading to increased bioconversion of isoflavones in soymilk. The concentration of genistein was decreased, accompanied by an increased concentration of genistein on fermentation in the presence of thiamine, niacinamide, biotin, calcium pantothenate and folic acid. Additionally, the supplementation of niacinamide, calcium pantothenate, biotin and folic acid also led to lower concentrations of malonyl daidzin, indicating increased hydrolysis of malonyl daidzin to daidzin. Results from the present study indicated that the supplementation of B-vitamins could enhance the bioactive potential and bioconversion of isoflavones in lactobacilli-fermented soymilk. Originality/value - This work has shown that the supplementation of B-vitamins in lactobacilli fermented soymilk has exerted in vitro ACE-inhibitory activity and increased the accumulation of bioactive isoflavone aglycones. To the authors' knowledge, this is the first evaluation reporting on such aspects.