Isolation and Anti-Melanogenic Activity of Polycarpol from Ganoderma lucidum Mycelia: Expanding the Functional Potential of Cultured Mycelial Biomass

Ganoderma lucidum is a medicinal mushroom widely recognized as a source of bioactive metabolites, particularly triterpenoids. Although most studies have focused on fruiting bodies and spores, the potential of cultured mycelial biomass as a source of functional secondary metabolites remains less explored. In this study, we isolated and characterized polycarpol from the mycelia of G. lucidum and evaluated its anti-melanogenic activity in B16F10 murine melanoma cells. Dried mycelia obtained after liquid culture were extracted with 70% ethanol, partitioned with ethyl acetate, and purified by repeated chromatographic separation. The isolated compound was identified as polycarpol by LC–ESI–MS, HR-MS/MS, and NMR spectroscopy, together with comparison with previously reported spectroscopic data. The anti-melanogenic activity of polycarpol was evaluated in α-MSH-stimulated B16F10 murine melanoma cells, a commonly used cellular model of melanogenesis. Polycarpol reduced α-melanocyte-stimulating hormone-induced cellular tyrosinase activity and melanin production at concentrations that did not markedly affect cell viability. Notably, 2 μg/mL (4.54 μM) polycarpol showed a melanin-inhibitory effect comparable to that of arbutin. Western blot analysis showed that polycarpol decreased the expression of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related protein-1. In addition, polycarpol suppressed CREB phosphorylation and modulated the MAPK signaling pathways. These findings suggest that polycarpol inhibits melanogenesis through regulation of MITF-associated melanogenic signaling. Overall, this study demonstrates that cultured G. lucidum mycelia can produce anti-melanogenic triterpenoids and highlights cultured mycelial biomass as a controllable fungal material for exploring anti-melanogenic triterpenoids, although further optimization is required to improve production efficiency.