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.

中文翻译：

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来自 Picrasma quassioides 的对映体 β-咔啉二聚体及其抗肝癌潜力

从 Picrasma quassioides 的茎中获得了四对对映异构 β-咔啉生物碱，(+/-)-kumudine AD，以及它们的生物合成相关化合物 kumudine E。它们的结构，包括绝对构型，是通过广泛的光谱数据结合电子圆二色性 (ECD) 光谱分析和量子力学 ECD 计算确定的。(+/-)-Kumudine A 拥有 β-咔啉-苯丙烷加合物的支架，这是自然界中此类 β-咔啉生物碱的第一个例子。通过SRB试验评估对肝细胞癌Hep3B和HepG2细胞的细胞毒性试验，表明(-)-Kumudine B比其对映异构体(+)-Kumudine B在Hep3B细胞中具有更强的作用。而且，