Tyrosinase inhibitory and antioxidant activities of three Bifidobacterium bifidum-fermented herb extracts

• Chinese herb extracts are potentially used for developing new cosmetic ingredients.
• Fermentation enhances physiological and biochemical activities of herb extracts.
• Fermented asparagus root extract has a great potential for cosmetic application.

Chinese herb extracts can potentially be used for developing new cosmetic or health food ingredients. This study evaluates the tyrosinase inhibitory and antioxidant activities of Bifidobacterium bifidum-fermented extracts of 3 Chinese herbs: walnut, Moutan Cortex Radicis (MCR), and asparagus root. First, the herbs were extracted using distilled water, 95% ethanol, 50% ethanol, 100% ethyl acetate, and 50% ethyl acetate. These extracts were further fermented using B. bifidum for different fermentation periods, and were evaluated for their tyrosinase inhibition activities, phenolic composition and content, and antioxidant activities. To understand user safety and the preliminary tyrosinase inhibitory mechanism of these extracts, we evaluated their cytotoxicity by analyzing the viability of normal skin fibroblast cells, CCD-966SK, and murine melanoma cells, B16F10. The 50% ethanol extracts of all 3 herbs exhibited the highest tyrosinase inhibition activities, phenolic content, and antioxidant activities. Furthermore, the physiological activities of fermented extracts were considerably higher than those of nonfermented extracts. The optimal IC50 values for tyrosinase inhibition for fermented walnut, MCR, and asparagus root extracts were 420, 380, and 260 μg/mL, respectively. Even at 300–900 μg/mL, all 3 fermented extracts examined were noncytotoxic to both CCD-966SK and B16F10 cells. Among all of the fermented herb extracts, asparagus root extract obtained using 50% ethanol before fermentation with B. bifidum for 24 h was found to be the best skin-whitening agent with the highest antioxidant potential.