X-ray and high-resolution 1H and 13C NMR of smooth muscle relaxant sesquiterpene lactones

Abstract

The structure and stereochemistry of four sesquiterpene lactones, budlein A (1), zaluzanin A (2), and glaucolides D (3a) and E (3b), isolated from Mexican Asteraceae species, for which only partial NMR data could be found in the literature, were determined. A combination of 1D and 2D high-resolution NMR experiments, such as DEPT, COSY, NOESY, ROESY, HMQC, HSQC, and HMBC, were used to completely assign the 1H and 13C spectra. The crystal structures of zaluzanin A (2) and glaucolide E (3b) were also determined. Glaucolides D and E have been previously reported to relax KCl-induced contraction in rat uterine smooth muscle; therefore, the effects of zaluzanin A and budlein A were examined in the same model. It was found that both compounds can relax contraction induced by KCl, but only zaluzanin A induced relaxation when contraction was induced with oxytocin. The preliminary biological test results according to these profiles are reported in this paper.Key words: NMR data, X-ray data, sesquiterpene lactones, Mexican Asteraceae, smooth muscle relaxant.