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 IC ₅₀ values of 258.7 ± 49.3 and 187.1 ± 27.5 μM, respectively (compared with acarbose, IC ₅₀ = 900.0 ± 3.0 μM) and moderate effects against PTP1B with IC ₅₀ values of 93.9 ± 12.3 and 64.1 ± 5.8 μM, respectively (compared with RK682, IC ₅₀ = 4.4 ± 0.3 l μM).