Sjögren M, Sjöberg U, Rannug U
Department of Genetic and Cellular Toxicology, Wallenberg Laboratory, Stockholm University, Sweden.
Mutat Res. 1994 Jun;321(4):229-39. doi: 10.1016/0165-1218(94)90074-4.
During the photolysis of tryptophan a large number of products is formed. In this study, aqueous solutions of tryptophan were irradiated by ultraviolet light during 5, 20 or 40 h. Each of the irradiated batches was divided into two aliquots, which were freeze-dried or extracted with chloroform. For each batch the latter extract was subsequently divided into a purified chloroform extract and a methanol extract. Aliquots of the purified chloroform extracts were fractionated and pooled, peakwise, into seven fractions. A recombined sample was also constructed. All extracts and samples were tested for mutagenicity using the standard Ames Salmonella assay. The results indicate an exposure time dependent increase in mutagenicity of the extracts, as seen with tester strain TA100 both with and without metabolic activation. The mutagenicity of the freeze-dried extracts well approximated the mutagenicity of the chloroform extracts, indicating that most mutagenicity can be extracted with chloroform. With the fractions the highest mutagenic responses were seen in the late, i.e., less lipophilic fractions. This response pattern seen in TA98 and TA100, mainly with S9 activation, was in contrast to the response of TA102 without S9, which was highest to the more lipophilic fractions. On a fraction level, no general exposure dependent increase of mutagenicity was observed. The results also show that photooxidation of tryptophan gives rise to a different spectrum of products compared to pyrolysis. Both processes result in compounds with strong biological effects. Photooxidation results in compounds with low genotoxicity and high Ah receptor affinity while pyrolysis generates compounds with high genotoxicity and low or no Ah receptor affinity.
在色氨酸的光解过程中会形成大量产物。在本研究中，色氨酸水溶液用紫外光照射5、20或40小时。每个照射批次均分为两份，一份冻干，另一份用氯仿萃取。对于每个批次，后一种萃取物随后又分为纯化的氯仿萃取物和甲醇萃取物。纯化氯仿萃取物的等分试样经分馏并按峰合并为七个馏分。还构建了一个重组样品。使用标准的鼠伤寒沙门氏菌Ames试验对所有萃取物和样品进行致突变性测试。结果表明，无论有无代谢活化，提取物的致突变性均随暴露时间增加，这在测试菌株TA100中可见。冻干提取物的致突变性与氯仿提取物的致突变性非常接近，表明大部分致突变性可用氯仿萃取。对于馏分，在后期馏分（即亲脂性较低的馏分）中观察到最高的致突变反应。在TA98和TA100中观察到的这种反应模式，主要是在有S9活化的情况下，与没有S9的TA102的反应相反，后者对亲脂性较高的馏分反应最高。在馏分水平上，未观察到致突变性随暴露的普遍增加。结果还表明，与热解相比，色氨酸的光氧化产生不同的产物谱。这两个过程都会产生具有强烈生物学效应的化合物。光氧化产生具有低遗传毒性和高Ah受体亲和力的化合物，而热解产生具有高遗传毒性和低或无Ah受体亲和力的化合物。
