Fungal exopolysaccharides are important natural products having diverse biological functions. In this study, exopolysaccharides from Fomitopsis castanea mycelia (FEPS) were prepared, and the highest mushroom tyrosinase inhibitory activity was found. FEPS were prepared from cultivation broth by ethanol precipitation method. The extraction yield and protein concentration of FEPS were 213.1 mg/l and 0.03%, respectively. FEPS inhibited mushroom tyrosinase with the half maximal inhibitory concentration (IC50) of 16.5 mg/ml and dose-dependently inhibited cellular tyrosinase activity (63.9% at 50 μg/ml, and 83.3% at 100 μg/ml) in the cell-free extract of SK-MEL-5 human melanoma cell and α-melanocytestimulating hormone (α-MSH)-stimulated melanin formation in intact SK-MEL-5 human melanoma cell. The IC50 of FEPS against NO production from RAW264.7 macrophage cells was 42.8 ± 0.64 μg/ml. By in vivo study using a zebrafish model, exposure of FEPS at 400 μg/ml to dechorionated zebrafish embryos for 18 h decreased the pigment density, compared to that without FEPS-treated control.
Keywords: Fomitopsis castanea; SK-MEL-5 human melanoma cells; exopolysaccharides; tyrosinase; zebrafish.