A new cytotoxic stilbene from <i>Paphiopedilum hirsutissimum</i> (Lindl. ex Hook.) Stein

A new <i>trans-</i>stilbene, (<i>E</i>)-2,4-<i>bis</i>(4-hydroxybenzyl)-3,5-dihydroxystilbene (<b>1</b>), and ten known compounds including stilbenoids (<b>2</b>, <b>7</b>, <b>8</b>, <b>10</b>), coumaric acid ester (<b>3</b>), flavonoids (<b>4</b>-<b>6</b>), aromatic aldehyde (<b>9</b>) and triterpenoid glycoside (<b>11</b>) were isolated from the leaves and roots of the lady slipper’s orchid <i>Paphiopedilum hirsutissimum</i> (Lindl. ex Hook.) Stein. The structures of these chemical constituents were determined based on their spectroscopic data and comparison with literature. <i>In vitro</i> cytotoxicity of all isolated compounds towards human hepatic cancer (HepG2) cell line was examined by MTT assay. Izalpinin (<b>6</b>) was potently cytotoxic to the cancer cells, with an IC₅₀ value of 4.62 ± 1.50 μM. Stilbenoids <b>2</b>, <b>7</b> and <b>8</b> also exhibited notable activity in the range of 6.31-6.68 μM. All compounds, except the new stilbene <b>1</b>, were non-toxic to normal fibroblast (OUMS-36) cell line.