<p>One new flavonol glycoside named visconoside C (<b>1</b>), together with seven known flavonol glycosides, quercetin 3-O-β-d-glucopyranoside 7-O-α-l-rhamnopyranoside (<b>2</b>), quercetin 7-O-α-l-rhamnopyranoside (<b>3</b>), astragalin (<b>4</b>), kaempferol 3-<i>O</i>-(4-<i>O</i>-acetyl)-<i>α</i>-l-rhamnopyranoside (<b>5</b>), kaempferol 7-<i>O</i>-<i>α</i>-l-rhamnopyranoside (<b>6</b>), kaempferitrin (<b>7</b>) and kaempferol 3-<i>O</i>-<i>β</i>-d-glucopyranoside 7-<i>O</i>-<i>α</i>-l-rhamnopyranoside (<b>8</b>) were isolated by various chromatography methods from the leaves of <i>Cleome viscosa</i> L. Their structures were elucidated by IR, UV, HR-ESI-MS and NMR (1D & 2D) experiments. The cytotoxicity and hepatoprotective activities using HepG2 human hepatoma cell line of <b>1</b> were measured by MTT assay. At the concentration of 25 μM and 50 μM, <b>1</b> showed cytotoxic activity against HepG2 cells (cell viability was decreased to 22.2 and 23.0%, respectively, compared with doxorubicin control), while at the concentration of 100 μM, <b>1</b> showed hepatoprotective activity against CCl<sub>4</sub>-induced hepatotoxicity on HepG2 cells (34.3%, compared with quercetin control).</p
