Editor's Choice for January 2021

January’s Editor’s Choice article is “A promising Ames battery for mutagenicity characterization of new dyes,” (https://onlinelibrary.wiley.com/doi/abs/10.1002/em.22417?af=R) by Gisela A. Umbuzeiro, Daniel A. Morales, Francine I. Vacchi, Anjaina F. Albuquerque, Malgorzata Szymczyk, Xinyi Sui, Nelson Vinueza, and Harold S. Freeman.

Testing of the mutagenicity of dyes poses a challenge because of the limited availability of the pure compound available for testing. Dyes have varied uses in food, textiles, plastics, paper, and cosmetics products. It is very important to have them tested thoroughly for their varied human consumption uses.

The Max Weaver Dye Library (MWDL), is a collection of 98,000 dye samples which was donated to North Carolina State University (NCSU) in 2014. NCSU took up this project to explore the possibility of usage of the dyes in various sectors. Initially they digitize 2700 dyes based on their structures (azo, anthraquinone, methine, nitro, and other substructures). Structural and spectroscopic data offered potential new uses for the dyes. For human consumption uses toxicological tests are needs for which mutagenicity data is essential. Mutagenicity data is mandatory for registration of compounds in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) by the European Union.

Ames is the standard mutagenicity test used to test compounds since 1970 to present day. The standard Ames test requires ~1 gm of the test article and uses standard OECD recommended Salmonella Typhimuriam strains TA1535, TA1537/TA97/ TA 97a , TA98, TA100 and TA102. However only 100 mg of dye substance is available from MWDL for dye testing.  Authors here proposed using miniature Ames that uses less amount of test article. The authors previously showed that YG1041strain is very sensitive to some types of dyes, especially the ones containing nitro and amino groups in their structure.

For this study the authors selected 15 dyes that represented different chemical classes across MWDL. Microplate agar protocol (MPA) was used where 12.5 mg or limit of solubility of the compound in 50 ul DMSO was tested. The test was conducted with or without S9 using eight S. typimurium TA97a, TA98, TA100, TA102, TA 1538 YG1041 and YG7108 strains.

The results showed that 6 of 15 dyes tested were mutagenic. The most sensitive was YG1041, followed by TA97a > TA98 > TA100 = TA1538 > TA102.  The two TA1537 and YG7108 strains did not show any mutagenicity. Here the authors concluded that dyes should be tested in a tired approach using YG1041 followed by TA97a, TA98, and TA100 strains using MPA version of Ames test. If positive result is obtained in the first strain tested, the compound should be determined as mutagenic, and other strain testing is not necessary.  A compound is determined non-mutagenic when negative results are obtained in five strains.  This work provides effective strategy to determine the mutagenicity of the dye compounds when limited amount of materials are available.

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