A new cadinane sesquiterpenoid from Eupatorium adenophorum and -glycosidase and AChE inhibitory activities of a gossypetin acylglucoside

To investigate the chemical constituents of Eupatorium adenophorum Spreng. (syn. Ageratina adenophora (Spreng.) R.M. King & H. Rob.) growing in Vietnam, the water-soluble fraction from the leaf methanol extract was fractionated by column chromatography. A new sesquiterpenoid, named adenophorone (1), was isolated along with 11 known compounds (2-12). The interpretation of HR-MS and 1D and 2D NMR spectroscopic data together with experimental and theoretical ECD calculations established the absolute stereostructure of compound 1. Two isolated flavonol glucosides 9 and 10 were subjected to enzyme inhibition assays. Gossypetin 5-O-(6 ''-(E)-caffeoyl)-beta-D-glucopyranoside (9) inhibited alpha-glycosidase activity with an IC50 value of 24.0 +/- 1.61 mu g/mL (80% inhibition at 256 mu g/mL) and acetylcholinesterase activity with an IC50 value of 217.60 +/- 15.47 mu g/mL (54% inhibition at 256 mu g/mL). Quercetagetin 7-O-beta-D-glucopyranoside (10) slightly inhibited the two enzymes (27% and 34% inhibition, respectively) at the maximal tested concentration of 256 mu g/mL. The present study is the first report on the chemical constituents of the water-soluble fraction of E. adenophorum. The study also provides some evidence for the alpha-glycosidase and acetylcholinesterase activities of the rare polyhydroxyflavonol acylglycoside gossypetin 5-O-(6 ''-(E)-caffeoyl)-beta-D-glucopyranoside. [GRAPHICS] .