Antitumour plants. Part 6. Novel modified germacranolides and other constituents of Eremanthus elaeagnus Schultz-bip (compositae)

Abstract

Extracts of the stem parts of the woody Composite Eremanthus elaeganus yielded lupeol acetate (1), friedelin (2), epifriedelinol (3), a mixture of sitosterols, the flavonoids tamarixetin (3,5,7,3′-tetrahydroxy-4′-methoxyflavone), genkwanin (5,4′-dihydroxy-7-methoxyflavone), and luteolin 7-methyl ether (5,3′,4′-trihydroxy-7-methoxyflavone), and the three novel modified germacranolides eremantholide A (5), B (6), and C (minor component)(7). The structures of eremantholides A and B were determined by X-ray crystallography, and a crystallographic comparison between the two structure is given. Eremantholide A reacts with propane-1-thiol by a novel 1,6-Michael-type addition which may simulate the mode of its cytotoxic action.