Preparation Of Active Guaianolides And Studies On Their Biosynthesis

Guaianolide is a major class of Sesquiterpene lactones with patent biological activity, they are mainly found in compositae plants, esp. Ixeris genus which are abundantly distributed throughout the northeastern China.Two active sesquiterpene lactones (lactone A and B) were isolated from I.sonchifolia with chromatograghy in porous resin, silica gel, etc. The content of lactone A and B in the native plant was measured with HPLC. The result showed that these compounds are richer in root than in the other parts in the plant.Aglycone A and B were purified by using acetylacetate extraction, chromatograghy in aluminum oxide, etc, with the support of analytic and preparative HPLC. The structures of aglycone A and B were elucidated on the basis of spectral methods.Their cytotoxic activities of lactones and aglycones were tested against A375-S2, Hela and L929 cell lines by using MTT assay. The result showed that lactones and aglycones inhibited proliferation of three tumor cell lines in a dose-dependent manner.It was obtained for the first time Ixeris genus from that a core region (ca 418bp) of Germacrene A synthase cDNA from I.sonchifolia with RT-PCR using the primers designed from the conserved amino acid motifs of the known sesquiterpene synthases. Its deduced product showed the 89.64% identity with the corresponding parts of the known Germacrene A synthases at the amino acid level.