Two New Sesquiterpene Lactones from Ixeris chinensis

Phytochemical investigation of Ixeris chinensis NAKAI (Asteraceae) has resulted in the isolation of a new guaianolide-type sesquiterpene lactone, ixerochinolide (1) as well as the related glucoside, ixerochinoside (2). In addition, the known guaianolides, 8β-hydroxy-3-oxo-guaia-4 (15), 10 (14), 11 (13) -trien-1α, 5a, 6β, 7αH-12, 6-olide (8β-hydroxydehydrozaluzanin), 8β, 15-dihydroxy-2-oxo-guaia-1 (10), 3, 11 (13) -trien-5α, 6β, 7αH-12, 6-olide (lactucin), 3β, 8α, 10α-trihydroxy-guaia-4 (15), 11 (13) -dien-1α, 5α, 6β, 7αH-12, 6-olide (10α-hydroxy-10, 14-dihydro-desacylcynaropicrin) and 3β-D-glucopyranosyloxy-8β- (p-hydroxyphenyIacetyloxy) -guaia-4 (15), 10 (14), 11 (13) -trien-1α, 5α, 6β, 7αH-12, 6-olide (8-epicrepioside) were identified. The structures were determined on the basis of spectral analyses, especially 1- and 2D NMR. Compound 1 exhibited significant cytotoxicity against human PC-3 tumor cells.