Heilmann J, Wasescha M R, Schmidt T J
Departement für Angewandte Biowissenschaften, Institut für Pharmazeutische Wissenschaften, Eidgenössische Technische Hochschule (ETH) Zürich, Switzerland.
Bioorg Med Chem. 2001 Aug;9(8):2189-94. doi: 10.1016/s0968-0896(01)00131-6.
The biological activities of sesquiterpene lactones have been attributed to their reactivity with the cysteine residues of functional proteins forming covalent bonds via Michael type addition. In the present study we investigated the influence of different L-cysteine (cys) and glutathione (GSH) concentrations on the cytotoxicity of the sesquiterpene lactones (STLs) helenalin, 11alpha,13-dihydrohelenalin acetate and chamissonolide against KB cells. Due to the significantly higher reactivity of the alpha-methylene-gamma-lactone (ML) towards cys as compared with the cyclopentenone (CP) site at physiological pH, addition of 20, 50 and 100 molar equivalents of cys decreased the cytotoxicity of helenalin and chamissonolide, whereas the cytotoxicity of 11alpha,13-dihydrohelenalin acetate remained unaffected. In contrast, the influence of GSH addition on the cytotoxicity of 11alpha,13-dihydrohelenalin acetate depends on the concentration of GSH added. Concentration-effect curves obtained for chamissonolide and GSH resembled the decline in cytotoxicity after cys addition. Helenalin showed a biphasic shape of the concentration-effect curve for the 100:1 GSH/helenalin ratio resembling at higher doses the chamissonolide and in lower doses the 11alpha,13-dihydrohelenalin acetate curve at 50-fold excess. These results can be explained by the different reactivity and equilibrium conditions for thiol addition of the two reactive centers of bifunctional STLs in cellular test systems and verified a clear correlation between the different reactivity of their electrophilic centers and the observed biological effects in in-vitro cell systems.
倍半萜内酯的生物活性归因于它们与功能蛋白的半胱氨酸残基发生反应，通过迈克尔型加成形成共价键。在本研究中，我们研究了不同浓度的L-半胱氨酸（cys）和谷胱甘肽（GSH）对倍半萜内酯（STLs）——艾里内酯、11α,13-二氢艾里内酯乙酸酯和异土木香内酯——对KB细胞细胞毒性的影响。由于在生理pH下，α-亚甲基-γ-内酯（ML）对半胱氨酸的反应性明显高于环戊烯酮（CP）位点，添加20、50和100摩尔当量的半胱氨酸可降低艾里内酯和异土木香内酯的细胞毒性，而11α,13-二氢艾里内酯乙酸酯的细胞毒性不受影响。相反，添加GSH对11α,13-二氢艾里内酯乙酸酯细胞毒性的影响取决于所添加GSH的浓度。异土木香内酯和GSH的浓度效应曲线类似于添加半胱氨酸后细胞毒性的下降。艾里内酯在100:1的GSH/艾里内酯比例下呈现双相浓度效应曲线，高剂量时类似于异土木香内酯，低剂量时类似于50倍过量的11α,13-二氢艾里内酯乙酸酯曲线。这些结果可以通过双功能STLs的两个反应中心在细胞测试系统中硫醇加成的不同反应性和平衡条件来解释，并证实了它们亲电中心的不同反应性与体外细胞系统中观察到的生物学效应之间存在明确的相关性。
