Anti-tyrosinase properties of different species of turmeric and isolation of active compounds from Curcuma amada

Turmeric is traditionally used as a skin cosmetic in some religious and cultural occasions on the Indian subcontinent. In this study, we compared the tyrosinase inhibitory properties of four Curcuma spp., namely, C. xanthorrhiza , C. aromatica, C. amada , and C. zedoaria . Bioassay-guided isolation and purification of tyrosinase inhibitors using silica gel column and high-performance liquid chromatography. Structural identification of the compounds was conducted using 1 H NMR, 13 C NMR, and liquid chromatography-tandem mass spectrometry. C. amada showed the highest tyrosinase inhibitory activity, with an IC 50 of 53.4 μg/mL. Therefore, it was chosen for the isolation and purification of tyrosinase inhibitors. The purified compounds were zederone (1) , furanodienone (2) , 1,5-epoxy-3-hydroxy-1-(3,4-dihydroxy-5-methoxyphenyl)-7-(4-hydroxyphenyl) heptanes (3) , 3,5-dihydroxy-1-(3,4-dihydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl) heptanes (4) and 1,5-epoxy-3-hydroxy-1-(3,4-dihydroxy-5-methoxyphenyl)-7-(4-hydroxy-3-methoxyphenyl) heptanes (5) . The IC 50 values for the mushroom anti-tyrosinase activity of compounds 1 , 2 , 3 , 4 , and 5 were 108.2, 89.2, 92.3, 21.7, and 41.3 µM, respectively. These compounds also inhibited intracellular tyrosinase activity, thus reducing melanin synthesis in B16F10 melanoma cells. Compound 4 showed significantly stronger anti-tyrosinase activity than that of arbutin (a positive control drug). No significant difference was observed in the tyrosinase inhibitory effect between compound 5 and arbutin. Our findings strongly suggest that C. amada is a promising source of natural tyrosinase inhibitors to prevent melanogenesis and could be used as a whitening cosmetic.