Scalemic diacetylenic spiroacetal enol ethers from the flowers of Tanacetum tatsienense

Six scalemic mixtures of previously undescribed diacetylenic spiroacetal enol ethers (DSEEs) and six scalemic mixtures of known DSEEs were isolated from the flowers of Tanacetum tatsienense. Except for E-epiden-dranthemenol, Z-O-acetyl-epi dendranthemenol, and Z-O-isovaleryl-epidendranthemenol, the remaining scale-mic mixtures of DSEEs were resolved by chiral HPLC, and their structures were determined through an analysis of HR-ESI-MS and NMR data. The absolute configurations of seven pairs of enantiomers and one pair of epimers were determined by comparing the experimental and calculated electronic circular dichroism (ECD) spectra. In addition, the inhibitory effects of all of the DSEEs on nitric oxide (NO) production were evaluated in LPS-stimulated RAW264.7 cells. The results showed that (+)-tatsienenol B had a weak inhibitory effect on NO production. The IC50 value of the compound was 19.78 +/- 0.78 mu M. This study is the first to report that DSEEs are isolable from plants as scalemic mixtures. Moreover, this study is the first to determine the absolute configu-rations of DSEEs by chiral resolution and ECD calculations.