Cytotoxic phenolics from Bulbophyllum odoratissimum

A phytochemical study of the whole plant of Bulbophyllum odoratissimum (J.E. Smith) Lindl (Orchidaceae) and cytotoxicity measurement of its isolated compounds have been carried out. The ethyl acetate extract yielded nine phenolics, identified as moscatin (1), 7-hydroxy-2,3,4-trimethoxy-9,10-dihydrophenanthrene (2), coelonin (3), densiflorol B (4), gigantol (5), batatasin III (6), tristin (7), vanillic acid (8) and syringaldehyde (9). Compounds 4 and 8 were discovered in the Bulbophyllum genus for the first time and all compounds, except for 9, have not been reported in this plant before. The isolated compounds were evaluated in vitro for their inhibitory ability against the growth of human leukaemia cell lines K562 and HL-60, human lung adenocarcinoma A549, human hepatoma BEL-7402 and human stomach cancer SGC-7901. Densiflorol B (4) the most active compound, exhibited IC50 values of 0.08–3.52 μg/ml against the five tested cell lines.