Tryptophan reaction with free radicals arisen from carbon tetrachloride in a model system. A mass spectrometric study

The interaction between free radicals derived from the thermal decomposition of carbon tetrachloride and N-acetyl-d, l-tryptophan ethyl ester (TRPAE) under anaerobic and aerobic conditions was studied. The structure of the reaction products formed was deciphered by the GC/MS analysis of their trimethylsilyl derivatives. Under anaerobic conditions no formation of reaction products was detected. Under aerobic conditions the following products were identified: 1. A chloro hydroxy unsaturated adduct of TRPAE (2 isomers). 2. A dichloro hydroxy unsaturated adduct of TRPAE. 3. 12 products which are different pyrrolo[2,3-b]indol derivatives. Some of the products appeared to have an hydroxyl group as a substituent, all of them contained chlorine and only one contained carbon from CCl4. Interestingly, the formation of those adducts not containing CCl3 would be missed during the regular procedures toxicologists use to determine the so-called 'covalent binding' employing (14)CCl4. Concerning the potential relevance of these findings, we hypothesize that if interactions similar to those here reported occurred at least in part during CCl4 poisoning, the resulting critical proteins containing tryptophan, e.g. membrane or other and enzymes containing the amino acid in their active center, might be impaired.