| Summary: | For our interest in the potential biologically active and structurally unique steroidal glycosides, continued phytochemical investigation of <i>Cynanchum taihangense</i> was carried out; twelve new seco-pregnane glycosides, cynataihosides I–L (<b>1</b>–<b>4</b>), M-T (<b>7</b>–<b>14</b>), and two known glycosides, glaucoside A (<b>5</b>) and atratcynoside F (<b>6</b>), were isolated from the 95% ethanol extract of <i>Cynanchum taihangense</i>. Two new aglycones were found among compounds <b>10</b>, <b>11</b>, <b>13</b>, and <b>14</b>. The structures of the glycosides were elucidated based on 1D and 2D NMR spectroscopic data, HR-ESI-MS analysis, and chemical evidence. The cytotoxicity of compounds against three human tumor cell lines (HL<i>-</i>60, THP-1, and PC-3) were evaluated by MTT assay. Compound <b>11</b> displayed significant cytotoxicity against THP-1 and PC-3 cell line with IC<sub>50</sub> values of 5.08 and 22.75 μm, respectively. Compounds <b>3</b> and <b>14</b> exhibited moderate and selective cytotoxicity on HL<i>-</i>60 and THP-1 with IC<sub>50</sub> values of 17.78 and 16.02 μm, respectively.
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