Anti-diabetic xanthones from the bark of Garcinia xanthochymus

An ethyl acetate extract the bark of Garcinia xanthochymus exhibited strong inhibition towards α-glucosidase and PTP1B with IC50 values of 0.3 ± 0.1 μg/mL and 2.3 ± 0.4 μg/mL, respectively. Chemical constituents of the extract were therefore examined, and two new compounds, xanthochymusxanthones A (1) and B (2), along with ten known xanthones (3–12), were isolated. Their structures were determined using spectroscopic methods, mainly 1D and 2D NMR. Inhibitory activity of the isolated compounds was then tested, and subelliptenone F (12) showed significant effect towards α-glucosidase with IC50 value of 4.1 ± 0.3 μM (compared with acarbose, IC50 = 900.0 ± 3.0 μM) whilst xanthochymusxanthone B (2) exhibited remarkable activity towards PTP1B with IC50 value of 8.0 ± 0.6 μM (compared with RK682, IC50 = 4.4 ± 0.3 μM). © 2017 Elsevier Ltd