Cytotoxic germacranolide sesquiterpene lactones from Carpesium triste var. manshuricum.

Four known germacranolide sesquiterpene lactones, 2alpha,5-epoxy-5,10-dihydroxy-6alpha-angeloyloxy-9beta-isobutyloxy-germacran-8alpha,12-olide (1), 2alpha,5-epoxy-5,10-dihydroxy-6alpha,9beta-diangeloyloxy-germacran-8alpha,12-olide (2, divaricin B), 2alpha,5-epoxy-5,10-dihydroxy-6alpha-angeloyloxy-9beta-(2-methylbutyloxy)-germacran-8alpha,12-olide (3) and 2alpha,5-epoxy-5,10-dihydroxy-6alpha-angeloyloxy-9beta-(3-methylbutyloxy)-germacran-8alpha,12-olide (4), were isolated from the chloroform-soluble fraction of the whole plants of Carpesium triste var. manshuricum. Their chemical structures were determined using spectroscopic methods, including 2D-NMR. All the isolates showed significant cytotoxicities (ED50 value: 4.3-16.8 microM) against five human tumor cell lines; A549, SK-OV-3, SK-MEL-2, XF498 and HCT15.