New bisabolane sesquiterpenes from the rhizomes of Curcuma xanthorrhiza Roxb. and their inhibitory effects on UVB-induced MMP-1 expression in human keratinocytes

Two new bisabolane sesquiterpenoids, 1 and 2, along with five known ones, 13-hydroxyxanthorrhizol (3), 12,13-epoxyxanthorrhizol (4), xanthorrhizol (5), β-curcumene (6), and β-bisabolol (7), were isolated from the rhizomes of Curcuma xanthorrhiza Roxb. The chemical structures of the new compounds were determined to be (7R,10R)-10,11-dihydro-10,11-dihydroxyxanthorrhizol 3-O-β-D-glucopyranoside (1) and (-)-curcuhydroquinone 2,5-di-O-β-D- glucopyranoside (2) on the basis of 1D- and 2D-NMR spectroscopic analyses and optical-rotation characteristics. Compounds 2 and 3 decreased MMP-1 expression in UVB-treated human keratinocytes by ca. 8.9- and 7.6-fold at the mRNA level, and by ca. 9.2- and 6.6-fold at the protein level, respectively. The results indicate that the isolated compounds may have anti-aging effects through inhibition of MMP-1 expression in skin cells.