Cytotoxic constituents of the leaves of Ixeris sonchifolia

The ethyl acetate extract of the leaves of Ixeris sonchifolia afforded two new and two known sesquiterpene lactone glucosides of the guaiane-type, together with a known alkenol glucoside. The known compounds were identified as ixerin Z (1), ixerin Z-6'-p-hydroxyphenylacetate (2), and (Z)-3-hexen-1-ol-beta-D-glucopyranoside (3), respectively. The structures of the new compounds were elucidated as 11,13a-dihydroixerin Z [4, 3-hydroxy-2-oxo-guaia-1(10), 3-dien-5alpha,6beta,7alpha,11betaH-12,6-olide-3-O-beta-D-glucopyranoside], and 3,10beta-dihydroxy-2-oxo-guaia-3,11(13)-dien-1alpha,5alpha,6alpha,7aH-12,6-olide-10-O-beta-D-glucopyranoside (5), respectively. The cytotoxicity of these compounds against human hepatocellular carcinoma cell (HepG2) and human melanoma cell (SK-MEL-2) was evaluated.