A new natural xanthone, 1,3-dihydroxy-6,7-dimethoxy-2,8-diprenylxanthone, together with four known compounds, fuscaxanthone C, 1,7-dihydroxyxanthone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone and 2-geranylemodin were isolated from the stem bark of Cratoxylum arborescens (Vahl) Blume. The structure elucidations were achieved through spectroscopic analyses. Compounds 1 and 5 showed moderate activity against the human small cell lung cancer NCI-H187 cell line with the IC50 values of 3.69 +/- 1.27 microg/mL and 3.08 +/- 0.73 microg/mL, respectively.