A new benzoquinone and a new stilbenoid from (Ridl.) Rolfe.

One new alkyl benzoquinone, paphionone (), one new stilbenoid, ()-6,5'-dihydroxy-2,3'-dimethoxystilbene (), and eight known stilbenoids and flavonoids (-) were isolated from the leaves and roots of (Orchidaceae). Their chemical structures were determined based on IR, ECD, MS and NMR analyses. Cytotoxicity of all isolated compounds towards human hepatocellular carcinoma (HepG2) cell line was examined by MTT assay. The -hydroxybenzyl substituted stilbene was potently cytotoxic to the cancer cells, with an IC value of 4.80 ± 1.10 μM (selectivity index = 20.83). All compounds were non-toxic to normal human embryo fibroblast (OUMS-36) cell line.