Marnewick J L, Gelderblom W C, Joubert E
Programme on Mycotoxins and Experimental Carcinogenesis, Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa.
Mutat Res. 2000 Nov 20;471(1-2):157-66. doi: 10.1016/s1383-5718(00)00128-5.
The antimutagenic properties of South African herbal teas were investigated using the Salmonella typhimurium mutagenicity assay. Aqueous extracts of fermented and unfermented rooibos tea (Aspalathus linearis) and honeybush tea (Cyclopia intermedia) both possess antimutagenic activity against 2-acetylaminofluorene (2-AAF) and aflatoxin B(1) (AFB(1))-induced mutagenesis using tester strains TA98 and TA100 in the presence of metabolic activation. A far less inhibitory effect was noticed against the direct acting mutagens, methyl methanesulfonate (MMS), cumolhydroperoxide (CHP), and hydrogen peroxide (H(2)O(2)) using TA102, a strain designed to detect oxidative mutagens and carcinogens. Depending on the mutagen used, the unfermented tea exhibited the highest protective effect. A similar response regarding the protection against mutagenesis was obtained when utilising different variations of the double layer Salmonella assay. The double layer technique proved to be more effective to detect the protective effect of the different tea preparations against the direct acting mutagens. With respect to indirect mutagens, the highest protection was noticed when the carcinogen was metabolically activated in the presence of the tea extract as compared with when the tea extract was incubated in a separate layer with the bacteria. The current data suggest that two mechanisms seem to be involved in the antimutagenicity of the tea extracts towards carcinogens that require metabolic activation: (i) the tea components may interfere with cytochrome P450-mediated metabolism of these mutagens and (ii) the direct interaction between the tea constituents, presumably the polyphenolic compounds, with the promutagens and/or the active mutagenic metabolites. However, the mild and/or lack of protection and in some cases even enhancement of mutagenesis induced by direct acting or oxidative mutagens, provide new perspectives regarding the role of the polyphenolic compounds known to exhibit antioxidant properties, in the protection against mutagenesis in the Salmonella assay. The present study provides the first evidence on the antimutagenic activity of honeybush tea and further evidence on the antimutagenicity of rooibos tea.
采用鼠伤寒沙门氏菌致突变性试验研究了南非草药茶的抗诱变特性。发酵和未发酵的路易波士茶（线叶金雀花）及蜜树茶（中间Cyclopia）的水提取物，在代谢活化存在的情况下，使用测试菌株TA98和TA100，对2-乙酰氨基芴（2-AAF）和黄曲霉毒素B(1)（AFB(1)）诱导的诱变均具有抗诱变活性。使用旨在检测氧化诱变剂和致癌物的TA102菌株时，对直接作用诱变剂甲磺酸甲酯（MMS）、氢过氧化枯烯（CHP）和过氧化氢（H(2)O(2)）的抑制作用要小得多。根据所使用的诱变剂不同，未发酵茶表现出最高的保护效果。当使用双层沙门氏菌试验的不同变体时，在防止诱变方面获得了类似的反应。双层技术被证明在检测不同茶制剂对直接作用诱变剂的保护作用方面更有效。对于间接诱变剂，与茶提取物与细菌在单独一层中孵育相比，当致癌物在茶提取物存在下进行代谢活化时，观察到最高的保护作用。目前的数据表明，茶提取物对需要代谢活化的致癌物的抗诱变作用似乎涉及两种机制：（i）茶成分可能干扰细胞色素P450介导的这些诱变剂的代谢，以及（ii）茶成分（大概是多酚化合物）与前诱变剂和/或活性诱变代谢物之间的直接相互作用。然而，对直接作用或氧化诱变剂诱导的诱变的轻微和/或缺乏保护，以及在某些情况下甚至诱变增强，为已知具有抗氧化特性的多酚化合物在沙门氏菌试验中防止诱变的作用提供了新的视角。本研究提供了关于蜜树茶抗诱变活性的首个证据以及关于路易波士茶抗诱变作用的进一步证据。
