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Background: Nostoc commune is an edible terrestrial cyanobacterium containing lipophilic pigments and other bioactive constituents. However, the effects of its lipophilic extracts on cellular melanogenesis remain unclear. Purpose: To determine whether a hexane extract of N. commune (NCHE) suppresses α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis and to clarify the underlying cellular mechanism. Methods: B16F1 murine melanoma cells were treated with α-MSH and NCHE. Cellular melanin content, intracellular tyrosinase activity, and the expression of melanogenesis-related genes and proteins were assessed. The effects of NCHE on cell viability, mushroom tyrosinase monophenolase activity, and antioxidant activity were also evaluated. Results: NCHE did not significantly reduce the viability of B16F1 cells or HaCaT keratinocytes at concentrations up to 5.0 µg/mL after 48 h. NCHE reduced α-MSH-induced melanin accumulation and intracellular tyrosinase activity in B16F1 cells. It significantly reduced Tyr mRNA expression at 2.5 and 5.0 µg/mL and Mitf mRNA expression at 5.0 µg/mL. Lower MITF protein levels were observed after 6 h and lower tyrosinase protein levels after 72 h, whereas MC1R, TYRP1, and DCT proteins showed no consistent reductions. NCHE did not significantly inhibit mushroom tyrosinase at concentrations up to 20 µg/mL. Its radical-scavenging and ferric-reducing activities were modest at the concentrations that suppressed melanogenesis. Conclusion: NCHE suppresses α-MSH-induced melanogenesis in B16F1 cells. This effect is associated with lower MITF and tyrosinase expression rather than direct inhibition of tyrosinase or strong antioxidant activity. Further chemical characterization is needed to identify the active lipophilic constituents of N. commune.
Research papers (academic journals)
