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-hydroxyphenylace-tate (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), $3-dien-5{\alpha},6{\beta},7{\alpha},11{\beta}H-12,6-olide-3-O-{\beta}-D-glucopyranoside],{\;}and{\;}3,10{\$beta}-dihydroxy-2-oxo-guaia-3,11(13)-dien-1{\alpha},5{\alpha},6{\alpha},7aH-12,6-olide-10-O-{\beta}-D-glucopyranoside$ (5), respectively. The cytotoxicity of these compounds against human hepatocellular carcinoma cell (HepG2) and human melanoma cell (SK-MEL-2) was evaluated.