Hexane Extract of Kaempferia galanga L. Suppresses Melanogenesis via p38, JNK and Akt

Abstract

Kaempferia galanga L . is one of the plants in Zingiberaceae family. It is used by people in many regions of Asia and Africa for relieving toothache, abdominal pain, muscular swelling and rheumatism. Tyrosinase is a key enzyme for melanogenesis, and hyperpigmentation is associated with abnomal accumulation of melanin pigment. This study aimed to investigate the inhibition of melanogenesis by hexane extract of Kaempferia galanga L. (HKG) in B16F10 melanoma cells. Cell-free tyrosinase, melanin contents, intracellular tyrosinase activity and western blot analysis were performed to elucidate the effects on anti-melanogenesis. Cytotoxicity of the extracts was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and determined the concentration of 12.5, 25 ㎍/ml. HKG significantly inhibited to activities of intracellular tyrosinase and melanin synthesis in the absence or presence of α-melanocyte stimulating hormone (α-MSH) with dose-dependent manner. And HKG inhibited the expression of tyrosinase, tyrosinase-related protein 1 (TRP-1) and tyrosinase-related protein 2 (TRP-2), regardless of the presence or absence of α-MSH. HKG also down–regulated phosphorylation of p38 and JNK, and up–regulated phosphorylation of Akt. These effects were not related to its cytotoxicity action. These results indicate that HKG has the potential to be a useful therapeutic agent for treating hyperpigmentation disorders and as a beneficial additive in whitening agents in cosmetics industry.