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A new xanthone from the bark of Calophyllum thorelii

A new xanthone, calothorexanthone, together with five known compounds, garbogiol, 1,4,8-trihydroxyxanthone, δ-tocotrienol, 1,7-dihydroxyxanthone and globuxanthone, was isolated from a petroleum ether extract of the bark of Calophyllum thorelii. Their structures were established on the basis of spectroscopic methods, mainly one- and two-dimensional NMR. Antioxidant activity of the isolated compounds was tested using DPPH free radical scavenging assay and some exhibited remarkable effects with IC50 of 13.63–17.46 µg mL−1.