Abstract: Phytohemical investigation of the EtOAc extract of leaves and stems of Bulbophyllum kwangtungense Schlecht., belonging to the orchid family was carried out. Two new stilbenods were isolated by repeat column chromatography and characterized: one is bibenzyl compound, 5-(2,3-dimethoxyphenethyl)-6-methylbenzo[d][1,3]dioxole(1), and the other dibenz[b,f]oxepine, 10,11-dihydro-2,7-dimethoxy-3,4-methylene-dioxy dibenzo[b,f]oxepine(2). Their structures were established on the basis of analyses of spectroscopic evidence, particularly by two-dimensional NMR spectroscopic analysis. Bibenzyl compound with a methyl group in the benzene ring is rarely found from natural sources. Natural oxepines are very rare, and most of them were reported to have good anti-tumor activities. In addition, anti-tumor activities of the new compounds were also evaluated. Among the compounds isolated, compound 2 showed anti-tumor activities with IC₅₀ value of 47.2 μg/mL in vitro against cultures of Hela cells.

Key words: Bulbophyllum kwangtungense, Oxepine, Bibenzyl compound