Isoflavone itself is less available in the body without the aid of intestinal bacteria. In this study, we searched for isoflavone-transforming bacteria from human fecal specimens (n = 14) using differential selection media. Isoflavone-transforming activity as the production of dihydrogenistein and dihydrodaidzein was assessed by high-performance liquid chromatography and we found Lactobacillus rhamnosus, named L. rhamnosus vitaP1, through 16S rDNA sequence analysis. Extract from Pueraria lobata (EPL) and soy hypocotyl extract were fermented with L. rhamnosus vitaP1 for 24 and 48 h at 37°C. Fermented EPL (FEPL) showed enhanced anti-tyrosinase activity and antioxidant capacities, important suppressors of the pigmentation process, compared with that of EPL (p < 0.05). At up to 500 μg/ml of FEPL, there were no significant cell cytotoxicity and proliferation on B16-F10 melanoma cells. FEPL (100 μg/ml) could highly suppress the content of melanin and melanosome formation in B16-F10 cells. In summary, Lactobacillus rhamnosus vitaP1 was found to be able to biotransform isoflavones in EPL. FEPL showed augmented anti-melanogenic potential.
Keywords: Lactobacillus rhamnosus; Pueraria lobata; chemical analysis; dihydrodaidzein; dihydrogenistein; microbiology.