Two new antidiabetic xanthones from the twigs of Garcinia oblongifolia

Two new xanthones, oblongixanthones I (1) and J (2), and seven known compounds (3–9), were isolated from an EtOAc extract of the twigs of Garcinia oblongifolia. Their structures were elucidated using spectroscopic methods, mainly 1 D and 2 D NMR. The antidiabetic effects of the two new compounds were evaluated using α-glucosidase and PTP1B inhibition assays. Both compounds displayed strong inhibition towards α-glucosidase with IC50 values of 258.7±49.3 and 187.1±27.5 μM, respectively (compared with acarbose, IC50 = 900.0±3.0 μM) and moderate effects against PTP1B with IC50 values of 93.9±12.3 and 64.1±5.8 μM, respectively (compared with RK682, IC50 = 4.4±0.3 l μM).