A new cadinane sesquiterpenoid from Eupatorium adenophorum and α -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)- β -D-glucopyranoside ( 9 ) inhibited α -glycosidase activity with an IC 50 value of 24.0 ± 1.61 μg/mL (80% inhibition at 256 μg/mL) and acetylcholinesterase activity with an IC 50 value of 217.60 ± 15.47 μg/mL (54% inhibition at 256 μg/mL). Quercetagetin 7- O - β -D-glucopyranoside ( 10 ) slightly inhibited the two enzymes (27% and 34% inhibition, respectively) at the maximal tested concentration of 256 μg/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 α -glycosidase and acetylcholinesterase activities of the rare polyhydroxyflavonol acylglycoside gossypetin 5- O -(6′′-( E )-caffeoyl)- β -D-glucopyranoside.