Garcicowanones C-E, three new hydrated-geranylated xanthones from the roots of Garcinia cowa Roxb. ex Choisy, and their α-glucosidase inhibition activities

Three new xanthones, garcicowanones C-E (1 − 3), and six known xanthones (4 − 9) were isolated from the roots of Garcinia cowa Roxb. ex Choisy. Their chemical structures were determined using spectroscopic technics, including HR-ESI-MS and 2 D NMR. All isolated compounds were evaluated for in vitro α-glucosidase inhibition. Cowanol (6) and norcowanin (8) had the most potent α-glucosidase inhibitory activity, with respective IC50 values of 33.5 ± 0.8 and 17.2 ± 0.3 µM, compared with the positive control, acarbose (IC50 257.3 ± 4.8 µM).