Extract of Ganoderma formosanum Mycelium as a Highly Potent Tyrosinase Inhibitor

In this study, the inhibitory effect of Ganoderma formosanum mycelium extracts on tyrosinase, the central regulatory enzyme being responsible for cutaneous pigmentation, was investigated in both cell-free and cellular enzymatic systems, as well as in phenotype-based zebrafish model. Bioassay-guided purification indicated that the ethyl acetate fraction of G. fromosanum mycelium ethanolic extract (GFE-EA) demonstrated the highest inhibition toward cell-free tyrosinase (IC50 = 118.26 ± 13.34 ppm). The secreted and intracellular melanin of B16-F10 cells were reduced by GFE-EA through suppression of tyrosinase activity (IC50 = 102.27 ± 9.49 ppm) and its protein expression. Moreover, GFE-EA decreased surface pigmentation level of zebrafish via down-regulation of tyrosinase activity. Most of all, there is no significant difference in morphology and mortality between control and GFE-EA treated groups. Not only does GFE-EA exhibit similar depigmenting efficacy to kojic acid with lower dosage (approximately one-seventh of dose), but show less toxicity to zebrafish. It is worth noting that GFE-EA is extracted from mycelium, which subverts the general concept that mycelium lacks certain bioactivities possessed by fruit bodies. Altogether, it would appear that GFE-EA has great potential for application in the cosmetics industry.