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Two new stilbenes, 2-(3',5'-dimethoxyphenyl)-6-hydroxy-5-methoxybenzofuran (1) and 3'-hydroxy-2,5'-dimethoxystilbene (2), together with seven known stilbenes (3, 5-10) and one flavanone (4), were isolated from the roots of Paphiopedilum godefroyae. Their chemical structures were determined on the basis of their spectroscopic data. These isolated compounds were evaluated for their cytotoxicity against human small cell lung cancer (NCI-H187) cell lines and an arylbenzofuran derivative, 5,6-dimethoxy-2-(3-hydroxy-5-methoxyphenyl)benzofuran (6), was shown to be strongly cytotoxic with an IC value of 5.10 μM.

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Three new stilbene dimers, paphiodianthins A-C (1-3), and nine known stilbenes, lignan and flavonoids (4-12) were isolated from the roots and leaves of Paphiopedilum dianthum (Orchidaceae). The structures of new compounds were elucidated from their NMR, HRESIMS and IR spectroscopic data. Cytotoxic activity of all isolated compounds was evaluated by in vitro MTT assay against two human cancer cell lines (MCF-7, Caco-2), doxorubicin-resistant and mitoxantrone-resistant MCF-7 sublines and a normal cell line (NIH/3T3). Stilbenes 1, 3, 10 and 11 were strongly cytotoxic to both cancer cell lines with IC 50 values ranging from 0.50 to 4.51 µM. Compounds 1, 10 and 11 were also active against drug-resistant MCF-7 sublines.