Enantiomeric β-carboline dimers from Picrasma quassioides and their anti-hepatoma potential

Abstract Four pairs of enantiomeric β -carboline alkaloids, (+/−)-kumudine A-D, along with their biosynthesis-related compound kumudine E, were obtained from the stems of Picrasma quassioides . Their structures, including the absolute configurations, were determined via extensive spectroscopic data combined with electronic circular dichroism (ECD) spectroscopic analyses and quantum mechanical ECD calculations. (+/−)-Kumudine A possessed a scaffold of β -carboline-phenylpropanoid adduct, which were the first examples of this type of β -carboline alkaloid from nature. The cytotoxicity assay against hepatocellular carcinoma Hep3B and HepG2 cells was evaluated by SRB assay, which showed that (−)-Kumudine B had stronger effect than its enantiomer (+)-Kumudine B in Hep3B cells. Moreover, further flow cytometry analysis also supported the enantioselectivity between (+)-Kumudine B and (−)-Kumudine B, suggesting that the compounds caused death of hepatoma cells through apoptosis induction.