Fermentation of Danggui Buxue Tang, an ancient Chinese herbal mixture, together with Lactobacillus plantarum enhances the anti-diabetic functions of herbal product

BACKGROUND: Danggui Buxue Tang (DBT), an ancient Chinese herbal decoction containing Astragali Radix and Angelicae Sinensis Radix at a ratio of 5: 1, is prescribed for menopausal women. Flavonoids and its flavonoid glycosides are considered as the major active ingredients within the herbal decoction; however, their amount is not controllable during the preparation. Besides, the aglycons within DBT are believed to have better gut absorption and pharmacological efficacy. METHODS: The herbal extract of DBT was fermented with Lactobacillus plantarum. The amounts of flavonoid glucosides and its aglycones in the fermented product were analyzed by using UPLC-MS/MS. In addition, in vitro assays were employed to evaluate the efficacy of the fermented DBT in regulating the activities of α-glucosidase, α-amylase and lipase, as well as their antioxidant capacity (DPPH and T-AOC assays) and anti-glycation property (BSA-methylglyoxal, BSA-fructose, and arginine-methylglyoxal models). RESULTS: The fermentation of DBT with L. plantarum drove a completed conversion of calycosin-7-O-β-D-glucoside and ononin to calycosin and formononetin, respectively. The chemical transformation could be probably mediated by β-glycosidase within the fermented product. Several in vitro assays corresponding to anti-diabetic functions were compared between parental DBT against its fermented product, which included the activities against α-glucosidase, α-amylase and lipase, as well as anti-oxidation and anti-glycation. The fermented DBT showed increased activities in inhibiting α-glycosidase, suppressing DPPH radical-scavenging and anti-glycation, as compared to the original herbal product. CONCLUSION: These results suggested that DBT being fermented with the probiotic L. plantarum could pave a new direction for fermentation of herbal extract, as to strengthen its pharmacological properties in providing health benefits.