Antitumor Effects Of Sesquiterpene Lactones From Crepidiastrum Sonchifolium And Molecular Cloning Of Germacrene A Synthase CDNA

Crepidiastrum sonchifolium (Bunge) is an annual composite plant which is abundantly distributed throughout the northeastern China. Among the chemical constituents of Crepidiastrum sonchifolium, sesquiterpene lactone is a major class with conspicuous biological activity.In our study of Crepidiastrum sonchifolium , two sesquiterpene lactone glucosides (including lactone glucoside 1 and 2) were isolated with chromatograghy in porous resin, silica gel and preparative HPLC etc. The structures of them were elucidated by analyses of spectra and comparison with published data. Lactone glucoside 1 was identified as 1(10), 3, 11(13)-guaiatriene-12, 6-olide-2-one-3-O-glucopyranoside, and lactone glucoside 2 was identified as 1(10), 3-guaiadiene-12, 6-olide-2-one-3-O-glucopyranoside.In this study, the combination of lactone glucosides was converted to lactone aglycones by hydrolysis, then they were isolated with chromatograghy in aluminum oxide and preparative HPLC etc. The structures of them were elucidated by analyses of spectra. Aglycone 1 was identified as3-hydroxy-1(10),3,11(13)-guaiatriene-12,6-olide-2-one and aglycone 2 was identified as 3-hydroxy-1(10),3-guaiadiene-12,6-olide-2-one.The antitumor effects of these four compounds were measured in vitro The studies demonstrate that lactone aglycones significantly inhibited proliferation of various cultured cells (A375-S2, Hela and L929) in a dose-dependent manner. MTT assay, photomicroscopical observation, showed that lactone aglycones induced apoptotic cell death in various cultured cells. Then the possible mechanism of cytotoxicity was investigated. It was observed that lactone aglycone 1 and 2 could affect DNA replication with the use of simian virus (SV40) DNA in vitro replication system. Therefore, we checked the effect of lactone aglycones on the ssDNA binding activity of RPA,which is a single-strand DNA binding protein that plays a pivotal role in DNA replication, repair, and homologous recombination. The result showed that aglycone 1 could inhibit the ssDNA binding activity of RPA in a dose dependent...