Melanogenesis inhibitory compounds from Saussureae Radix.

Ten compounds were isolated from the EtOAc soluble part of the MeOH extract of Saussureae Radix, with their effects on melanin production also evaluated in B-16 mouse melanoma cell lines stimulated with 3-isobutyl-1-methylxanthine (IBMX), an elevator of cellular cAMP. The compounds were identified as aplotaxene (1), 1 beta-hydroxy arbusculin A (2), costunolide (3), dehydrocostuslactone (4), 11 beta,13-dihydrocostunolide (5), reynosin (6), heptadec-(9Z)-enoic acid (7), beta-sitosterol (8), linoleic acid methyl ester (9) and betulinic acid methyl ester (10). Compounds 2, 9 and 10 were identified from Saussureae Radix for the first time. Furthermore, compounds 2, 3 and 6 showed potent inhibitory effects on the IBMX-induced melanogenesis, in dose-dependent manners, with IC50 values of 11, 3 and 2.5 microg/mL, respectively. As a positive control, arbutin exhibited an IC50 value of 29 microg/mL.