Three pairs of enantiomeric neolignans 1a/1b–3a/3b were isolated from the stems of Picrasma quassioides, and separated successfully by chiral-phase HPLC. Their structures were established by comprehensive spectroscopic analyses as well as ECD spectroscopy. The in vitro cytotoxicity of the isolates was evaluated against human hepatocellular carcinoma HepG2 and Hep3B cells. Among them, 1 and its enantiomers 1a/1b, 3 and 3a/3b displayed similar cytotoxicity in pair-wise comparison against HepG2 and Hep3B cells, and the similar effects of 2 and 2a/2b were found in Hep3B cells. Interestingly, 2a and 2b had different cytotoxic activities on HepG2 cells with IC₅₀ values of 35.6 μM and 104.4 μM, respectively. In addition, 2 exerted middle cytotoxicity against HepG2 cells with an IC₅₀ value of 78.6 μM. The different cytotoxicity between enantiomers 2a and 2b attracted our interest. To investigate the underlying mechanisms responsible for the distinct cytotoxicity, we further assessed the effects of 2a and 2b on cell cycle distribution, cell apoptosis and reactive oxygen species (ROS) generation. The results indicated that 2a had more significant effect than 2b on apoptosis induction and ROS generation, but both had no obvious effect on cell cycle of HepG2 cells. It is concluded that the different configurations of 2a/2b determined the enantioselective cytotoxicity on HepG2 cells through apoptosis induction and ROS generation.

从古生Picrasma quassioides的茎中分离出三对对映体新木脂素1a / 1b – 3a / 3b，并通过手性相HPLC成功分离。它们的结构是通过综合光谱分析和ECD光谱确定的。在体外分离株的细胞毒性抗人肝癌HepG2和Hep3B细胞进行评价。其中1及其对映异构体1a / 1b，3和3a / 3b在对HepG2和Hep3B细胞进行成对比较时显示出相似的细胞毒性，并且在Hep3B细胞中发现了2和2a / 2b的相似作用。有趣的是，2a和2b对HepG2细胞具有不同的细胞毒活性，IC ₅₀值分别为35.6μM和104.4μM。此外，2对HepG2细胞具有中等细胞毒性，IC ₅₀值为78.6μM。对映异构体2a和2b之间不同的细胞毒性引起了我们的兴趣。为了研究引起不同细胞毒性的潜在机制，我们进一步评估了2a和2a的作用。图2b关于细胞周期分布，细胞凋亡和活性氧（ROS）的产生。结果表明2a对细胞凋亡的诱导和ROS的产生比2b具有更显着的作用，但对HepG2细胞的细胞周期均无明显作用。结论是2a / 2b的不同构型决定了通过凋亡诱导和ROS产生对HepG2细胞的对映选择性细胞毒性。