Two new crotonic acid esters and their anti-vitiligo activity from Artemisia mongolica

A phytochemical investigation of the whole plant of Artemisia mongolica led to the isolation of two new crotonic acid esters with an alkylated glucose moiety, 7E-Hexene-5-ly-[6′-O-(2E-butyryl alkenyl)]-O-β-D-Glucopyranoside (1) and 7-methyl-pentane-5-ly-[6′-O-(2E-butyryl alkenyl)]-O-β-D-Glucopyranoside (2), together with nine known compounds, 1H-indole-3-hydroxyacetyl (3), indazole (4), peruvianoxide (5), 10-hydroxygeraniol (6), dihydrololiolide (7), ficusic acid (8), roseotoxin B (9), chrysosplenetin B (10), and kaempferol (11). Their structures were elucidated on the basis of spectroscopic evidence (IR, 1 H NMR, 13C NMR and 2D NMR) and MS. Compound 1 could significantly improve the relative tyrosinase activity (122.4%, 50 µM) and relative melanin content (145.9%, 50 µM) compared with the positive control 8-methoxypsoralen (120.1%, 138.6%, 50 µM). These compounds were first reported from A. mongolica.