Xanthones from the twigs of Garcinia oblongifolia and their antidiabetic activity.

Three new xanthones, oblongixanthone F-H (1-3), along with eight known xanthones (4-11), were isolated from an EtOAc extract of the twigs of Garcinia oblongifolia. Their structures were elucidated by spectroscopic analysis including 1D- and 2D-NMR spectroscopy and mass spectrometry. The antidiabetic effects of all isolated compounds were evaluated by in vitro α-glucosidase and PTP1B inhibition assays. Compound 11 was the most active compound, and inhibited α-glucosidase and PTP1B with IC50 values of 1.7±0.5 and 14.1±3.5µM, respectively.