Antiproliferative Pterocarpans and Coumestans from <i>Lespedeza bicolor</i>

Abstract

Chromatographic purification of a methanol extract of the roots of <i>Lespedeza bicolor</i> led to the isolation of four new pterocarpans (<b>1</b>-<b>4</b>), two new coumestans (<b>6</b> and <b>7</b>), two new arylbenzofurans (<b>8</b> and <b>9</b>), and the known pterocarpan 1-methoxyerythrabyssin II (<b>5</b>). Their structures were identified using NMR spectroscopy, UV spectroscopy, and mass spectrometry. Cytotoxicity assays showed that compounds <b>1</b>-<b>9</b> exerted antiproliferative effects on blood cancer cells. Of these compounds, <b>1</b> and <b>6</b> induced mitochondrial depolarization and induced apoptosis in Jurkat cells. These compounds promoted cell death by inducing cell-cycle arrest at the G1 stage, reducing levels of BCL2, and increasing cleavage of PARP-1. These findings indicate that <b>1</b> and <b>6</b> are possible lead compounds for the treatment of human leukemia cells via intracellular signaling.