中文摘要：

采用抗肿瘤活性追踪法对采自中国南海西沙群岛永兴岛柔荑软珊瑚Nephthea sp．中抗肿瘤活性成分进行研究，报道了两种具有细胞毒活性的甾醇化合物，经过MS，IR，^1H NMR，^13C NMR（DEPT），HSQC和HMBC等光谱技术鉴定为：24-甲基胆甾-5-烯-3β，8β-二醇（1）和24-亚甲基胆甾-4-烯-3β，6β-二醇（2），化合物1为新化合物，利用X—ray单晶衍射技术验证化合物2的立体结构．化合物1对肝癌细胞（BEL-7402），小鼠白血瘤细胞（P388）和人结肠癌细胞（LOVO）作用的IC50值分别为18．0，25．5和20．6μg／mL；化合物2对肿瘤细胞P388和人乳腺癌细胞（MCF）作用的IC50值分别为1．0和2．5μg／mL．

英文摘要：

Two cytotoxic sterols have been isolated from Nephthea sp. collected from Xisha islands of the South China Sea by bioassay-guided isolation. Their structures were established as 24-methylcholestan-5- ene-3β,8β-diol （1） and 24-methylenecholestan-4-ene-3β,6β-diol （2） by MS, IR, ^1H NMR, ^13C NMR （DEPT）, HSQC and HMBC analysis. Sterol 1 is a previously unknown compound and the stereochemistry of sterol 2 has been validated by X-ray diffraction analysis for the first time. Sterol 1 exhibited cytotoxicity against BEL-7402, P388 and LOVO cells （IC50 18.0, 25.5 and 20.6 μg/mL, respectively）. Sterol 2 also showed significant cytotoxicity against P388 and MCF cells （IC50 1.0 and 2.5 μg/mL, respectively）.