Xu R, Zhao W, Xu J, Shao B, Qin G
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China.
Adv Exp Med Biol. 1996;404:371-82. doi: 10.1007/978-1-4899-1367-8_30.
In our recent studies on bioactive saponins, two Chinese medicinal plants: Mussaenda pubescens Ait.f (Rubiaceae) and Clematis chinensis Osbeck (Ranunculaceae), were investigated. Of the two medicinal plants, M. pubescens is a Chinese folk medicine which has been used as a diuretic, antiphlogistic, diaphoretic and antipyretic agent, and has also been used to detoxify mushroom poisons and to terminate early pregnancy. Clematis chinensis is a Chinese traditional medicine which has been used as an analgesic, diuretic, antitumor, antiinflammatory and insecticidal agent for ages. As a result of our studies, eighteen saponins were identified from M. pubescens, among which seventeen were new compounds, while eleven saponins were isolated from C. chinensis, three of which were new compounds. In the course of our structural studies, mass fragment analysis in FAB-mass spectra and 1H- and 13C-NMR spectra were used to determine the structures of the sapogenin and oligosaccharide moieties. In those more complicated and minor saponins, various 2D-NMR experiments were carried out on 400-, 500- or 600-MHz NMR instruments, which permitted the identification of new sapogenins in glycoside form. In addition, it was also possible to assign all the proton and carbon signals of the sugar units on the basis of 1H-1H DQF COSY, TOCSY and HMQC spectra, which further permitted the establishment of linkage sites and sequences among the sugar units and aglycones by means of NOESY, ROESY and HMBC spectra. When the proton signals of sugar units are overlapped seriously in 1H-NMR spectra, peracetylation is a very helpful technique which can spread proton signals in wider range, thus simplifying their assignment by means of 2D-NMR spectra. When some of the sugar proton signals of a peracetylate are also overlapped coincidentally, alternation of deuterated solvents for measuring NMR spectra can circumvent the difficulties. Pharmacological tests indicated that mussaendoside O, the most abundant saponin from M. pubescens, can inhibit significantly the secretions of the lachrymal and salivary glands induced by galanthamine, and can also inhibit the contraction of the isolated longitudinal muscle strip from guinea pig ileum evoked by an M-Ach receptor agonist (carbachol, 10(-6) M) at concentrations of 10(-4) and 10(-5) M. From these results, the saponin should be an antagonist of the M-Ach receptor, and was presumed to be responsible for its antitoxicity activity toward some mushroom poisons of medicinal plant origin. In addition, mussaendoside O also showed immunopromotive and hemolytic activities.
在我们最近关于生物活性皂苷的研究中，对两种中国药用植物进行了研究：玉叶金花（茜草科）和威灵仙（毛茛科）。在这两种药用植物中，玉叶金花是一种中国民间药物，一直被用作利尿剂、消炎药、发汗剂和退烧药，还被用于解毒蘑菇中毒和终止早期妊娠。威灵仙是一种中国传统药物，长期以来一直被用作止痛剂、利尿剂、抗肿瘤剂、抗炎剂和杀虫剂。我们的研究结果表明，从玉叶金花中鉴定出18种皂苷，其中17种是新化合物，而从威灵仙中分离出11种皂苷，其中3种是新化合物。在我们的结构研究过程中，利用快原子轰击质谱（FAB - mass）中的质量碎片分析以及1H - 和13C - NMR光谱来确定皂苷元及低聚糖部分的结构。对于那些更复杂和含量较少的皂苷，在400 - 、500 - 或600 - MHz NMR仪器上进行了各种二维核磁共振（2D - NMR）实验，这使得能够鉴定出糖苷形式的新皂苷元。此外，还可以根据1H - 1H双量子滤波相关谱（DQF COSY）、全相关谱（TOCSY）和异核多量子相干谱（HMQC）对糖单元的所有质子和碳信号进行归属，进而通过核Overhauser效应谱（NOESY）、旋转Overhauser效应谱（ROESY）和异核多键相关谱（HMBC）确定糖单元与苷元之间的连接位点和序列。当糖单元的质子信号在1H - NMR光谱中严重重叠时，全乙酰化是一种非常有用的技术，它可以使质子信号在更宽的范围内展开，从而通过二维核磁共振光谱简化其归属。当全乙酰化物的一些糖质子信号也偶然重叠时，更换用于测量核磁共振光谱的氘代溶剂可以解决这些困难。药理试验表明，玉叶金花苷O是玉叶金花中含量最高的皂苷，它能显著抑制加兰他敏诱导的泪腺和唾液腺分泌，并且在浓度为10(-4)和10(-5) M时，还能抑制由M - 乙酰胆碱受体激动剂（卡巴胆碱，10(-6) M）引起的豚鼠回肠离体纵肌条收缩。根据这些结果，该皂苷应该是M - 乙酰胆碱受体的拮抗剂，并推测它对某些药用植物来源的蘑菇中毒具有解毒活性。此外，玉叶金花苷O还表现出免疫促进和溶血活性。
