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1062140 
Journal Article 
Permeability and toxicity characteristics of L-cysteine and 2-methyl-thiazolidine-4-carboxylic acid in Caco-2 cells 
Kartal-Hodzic, A; Marvola, T; Schmitt, M; Harju, K; Peltoniemi, M; Sivén, M 
2013 
1 
Pharmaceutical Development and Technology
ISSN: 1083-7450
EISSN: 1097-9867 
18 
6 
1288-1293 
English 
22356486 
WOS:000323730700003 
Acetaldehyde is a known mutagenic substance and has been classified as a group-one carcinogen by the WHO. It is possible to bind acetaldehyde locally in the gastrointestinal (GI) tract with the semi-essential amino acid l-cysteine, which reacts covalently with acetaldehyde and forms compound 2-methyl-thiozolidine-4-carboxylic acid (MTCA). The Caco-2 cell line was used to determine the permeation of l-cysteine and MTCA, as well as the possible cell toxicity of both substances. Neither of the substances permeated through the Caco-2 cells at the concentrations used in this study, and only the highest concentration of MTCA affected the viability of the cells in the MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) test. These results showed that when l-cysteine is administered in formulations releasing it locally in the lower parts of GI tract, it is not absorbed but can react with acetaldehyde, and that neither l-cysteine nor MTCA is harmful to the cells when present locally in the upper parts of GI tract. This study also shows that MTCA is sensitive at a lower pH of 5.5. Since stable MTCA is desired in different parts of the GI tract, this observation raises concern over the influence of lower pH on l-cysteine-containing product ability to bind and eliminate carcinogenic acetaldehyde.