Anti-melanogenic effect of Ajuga decumbens callus extract cultured by irradiating LED blue light in α-MSH-induced B16F10 melanoma cells

This study investigated the effects of blue light irradiation during the callus culture of Ajuga decumbens on its whitening activity and underlying mechanisms.High-performance liquid chromatography analysis revealed that callus extracts cultured under blue light (ADB) exhibited a broader chromatographic profile and increased accumulation of phenolic and flavonoid compounds, including apigenin, compared with those cultured under conventional conditions (AD).Cytotoxicity was first evaluated using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to determine non-toxic concentrations, and subsequent experiments were conducted using AD and ADB at 25, 50, and 100 µg/mL.Both extracts exhibited inhibitory effects on melanin production and tyrosinase activity; however, ADB showed markedly stronger anti-melanogenic activity than AD.To further elucidate the mechanism underlying this enhanced whitening effect, the expression levels of melanogenesis-related proteins were analyzed by western blotting.AD suppressed the expression of tyrosinase-related protein (TRP)-1, tyrosinase, and MITF but unexpectedly increased TRP-2 expression.In contrast, ADB effectively downregulated all four melanogenic markers, including TRP-1, TRP-2, tyrosinase, and MITF.Notably, the expression levels of TRP-1 and tyrosinase in ADB-treated cells were comparable to those of the α-melanocyte stimulating hormone untreated group, while TRP-2 and MITF levels were significantly lower.These findings demonstrate that blue light irradiation during A. decumbens callus culture enhances the production of bioactive secondary metabolites with potent whitening activity.Collectively, this study suggests that blue light-cultured A. decumbens callus extract holds significant potential as a novel skinwhitening functional ingredient.