Diverse Prenylated Bibenzyl Enantiomers from the Chinese Liverwort <i>Radula apiculata</i> and Their Cytotoxic Activities.
Zhang CY, Gao Y, Zhou JC, Xu ZJ, Qiao YN, Zhang JZ, Lou HX.
An EtOH extract of the Chinese liverwort <i>Radula apiculata</i> showed cytotoxic activity against the A549 lung cancer cell line. Bioassay-guided fractionation led to the isolation of 19 prenylated bibenzyls, including eight previously unknown dimeric prenylated bibenzyls [radulapins A-H (<b>1</b>-<b>8</b>)], four new prenylated bibenzyls (<b>9</b>-<b>12</b>), and seven known compounds (<b>13</b>-<b>19</b>). Compounds <b>1</b>-<b>11</b> were analyzed as racemates by chiral-phase separation. Their structures were determined by detailed analysis of their spectroscopic data and by single-crystal X-ray diffraction, chiral resolutions, and electronic circular dichroism measurements. Using an MTT assay, these dimers (<b>1</b>-<b>8</b>) showed significant cytotoxic activity against a panel of human cancer cell lines. Further investigation revealed that compound <b>4</b> induces PC-3 cell death via mitochondrial-derived apoptosis.