Sudan I
Template:Chembox Sudan I (also known as CI Solvent Yellow 14 or Solvent Orange R)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is an organic compound typically classified as an azo dye.<ref name="Ullmann">Template:Ullmann</ref> It is an orange-red solid, used to color waxes, oils, petrol, solvents, and polishes. Historically, Sudan I used to serve as a food coloring agent, notably for curry powder and chili powder. However, along with its derivatives Sudan III and Sudan IV, the compound has been banned for use in food in many countries (including the United States and the European Union)<ref name="pmid18418879">Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> due to its classification as a category 3 carcinogen by the International Agency for Research on Cancer (not classifiable as to its carcinogenicity in humans).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Nevertheless, Sudan I remains valuable as a coloring reagent for non-food-related uses, such as in the formulation of orange-colored smoke.
ApplicationEdit
The Sudan dyes are a group of azo compounds which have been used to color hydrocarbon solvents, oils, fats, waxes, shoes, and floor polishes. As recently as 1974, about Template:Convert of Sudan I, Template:Convert of Sudan II, Template:Convert of Sudan III, and Template:Convert of Sudan IV was produced in the United States.Template:Citation needed
Sudan I and Sudan III (1-(4-(phenyldiazenyl)phenyl) azo naphthalen-2-ol) are primarily used for the same application.<ref>Chailapakul, O.; Wonsawat, W.; Siangproh, W.; et al., Analysis of Sudan I, Sudan II, Sudan III, and Sudan IV in food by HPLC with electrochemical detection: Comparison of glassy carbon electrode with carbon nanotube-ionic liquid gel modified electrode. Food Chemistry 2008, 109 (4), 876-882</ref>
Sudan III melts at a 68°C (154.4°F), a much lower temperature than Sudan I, which melts at 131°C (268°F).
SynthesisEdit
There are two steps in synthesizing this compound:
The first step is the preparation of a benzene diazonium chloride solution, a diazonium salt created from the reaction of aniline with nitrous acid generated by the reaction of sodium nitrite and hydrochloric acid.
The second step involves adding the solution of the diazonium salt to 2-naphthol, to produce the diazo dye.
Sudan I is prone to photodegradation when exposed to light. This process involves the breakdown of the dye due to the interaction with singlet oxygen and free radicals. As a result, the colorfastness of Sudan I on materials is poor.<ref>Griffiths, J.; Hawkins, C., Synthesis and photochemical stability of 1-phenylazo-2-naphthol dyes containing insulated singlet oxygen quenching groups. Journal of Applied Chemistry and Biotechnology 1977, 27 (4), 558-564</ref>
Degradation and metabolismEdit
The metabolism of Sudan I, as characterized in rabbits, involves both oxidative and reductive reactions.<ref>Childs, J. J.; Clayson, D. B., The metabolism of 1-phenylazo-2-naphthol in the rabbit. Biochemical Pharmacology 1966, 15 (9), 1247-1258</ref>
The biological breakdown of the nitrogen-nitrogen bond by hydrogenation of the Sudan I molecule (azo-reduction) produces aniline and 1-amino-2-naphthol. This reaction appears to contribute to the detoxification observed in animal studies. After oxidation of Sudan I, C-hydroxylated metabolites are formed as major oxidation products and are excreted in urine. These metabolites are also found after oxidation with rat hepatic microsomes in vitro.Template:Citation needed
The C-hydroxylated metabolites may be considered as the detoxification products, while the benzene diazonium ion (BDI), formed by the microsome-catalyzed enzymatic splitting of the azo group of Sudan I, reacts with DNA in vitro.<ref name=Stiborova1>Stiborova, M.; Asfaw, B.; Anzenbacher, P.; Hodek, P., A New Way To Carcinogenicity Of Azo Dyes - The Benzenediazonium Ion Formed From A Non-Aminoazo Dye, 1-Phenylazo-2-Hydroxynaphthalene (Sudan-I) By Microsomal-Enzymes Binds To Deoxyguanosine Residues Of DNA. Cancer Letters 1988, 40 (3), 327-333</ref><ref name=Stiborova2>Stiborova, M.; Asfaw, B.; Frei, E., Peroxidase-Activated Carcinogenic Azo-Dye Sudan-I (Solvent Yellow-14) Binds To Guanosine In Transfer-Ribonucleic-Acid. General Physiology and Biophysics 1995, 14 (1), 39-49</ref> The major DNA adduct formed from this reaction is the 8-(phenylazo)guanine adduct, which was also found in the liver DNA of rats who were exposed to Sudan I.
The formation of C-hydroxylated metabolites and DNA-adducts from Sultan I oxidation was also demonstrated with human cytochrome P450 (CYP) enzymes, with CYP1A1 being the major enzyme involved in the oxidation of Sudan I in human tissues rich in this enzyme, while CYP3A4 is also active in human liver.Template:Citation needed
CYP1A1 constitutes less than 0.7% of the total hepatic CYP expression in human livers but can be responsible for up to 30% of the oxidation of Sudan I in a set of human liver microsomes.<ref name="Matsumura">Matsumura, S.; Ikeda, N.; Hamada, S.; et al., Repeated-dose liver and gastrointestinal tract micronucleus assays with CI Solvent Yellow 14 (Sudan I) using young adult rats. Mutation research. Genetic toxicology and environmental mutagenesis 2015, 780-781, 76-80</ref> Moreover, Sudan I strongly induces CYP1A1 in rats and human cells in culture due to the activation of the cytosolic aryl hydrocarbon receptor.<ref>Lubet, R. A.; Connolly, G.; Kouri, R. E.; et al., Biological effects of the Sudan dyes: role of the Ah cytosolic receptor. Biochemical Pharmacology 1983, 32 (20), 3053-3058</ref>
In addition to oxidation by CYP enzymes, Sudan I and its C-hydroxylated metabolites are oxidized by peroxidases, such as a model plant peroxidase and the mammalian enzyme cyclooxygenase. In bladder tissue, CYP enzymes are not detectable, but relatively high levels of peroxidases are expressed. As a consequence, DNA, RNA, and protein adducts are formed.Template:Efn Therefore, peroxidase-catalyzed activation of Sudan I has been suggested as mechanism. This is similar to other carcinogens, such as the carcinogenic aromatic amines.Template:Efn
It has been suggested that a CYP- or peroxidase-mediated activation of Sudan I or a combination of both mechanisms may be responsible for the organ specificity of this carcinogen for the liver and urinary bladder in animals.<ref>Stiborová, M.; Martínek, V.; Rýdlová, H.; et al., Sudan I Is a Potential Carcinogen for Humans Evidence for Its Metabolic Activation and Detoxication by Human Recombinant Cytochrome P450 1A1 and Liver Microsomes. Cancer Research 2002, 62 (20), 5678-5684</ref> The Sudan I metabolites formed by peroxidase are much less likely to be formed at physiological conditions because in vivo there are many nucleophilic molecules present which scavenge the Sudan I reactive species.<ref>Semanska, M.; Dracinsky, M.; Martinek, V.; et al., A one-electron oxidation of carcinogenic nonaminoazo dye Sudan I by horseradish peroxidase. Neuro Endocrinology Letters 2008, 29 (5), 712-716</ref> Hence, the formation of adducts in the Sudan I reactive species with nucleophilic species (such as DNA, tRNA, proteins, polynucleotides, and polydeoxynucleotides) seems to be the preferred reaction under physiological conditions, with deoxyguanosine as the major target for Sudan-I DNA binding, followed by deoxyadenosine.<ref name="Stiborova2" />
Effect on humansEdit
Sudan I is determined to be a health hazard by EU chemical regulators as well as the IARC.<ref name=Fox>Fox, M. R., Dye-makers of Great Britain. 1856-1976: A History of Chemists, Companies, Products and Changes ICI: Manchester, 1987</ref> It may cause allergic skin reactions and skin irritation. Exposure to the skin can happen by textile workers being subjected to direct exposure, or by wearing tight-fitting textiles dyed with Sudan I. Allergic reactions are induced when the azo dye binds to the human serum albumin (HSA), forming a dye-HSA conjugate which immunoglobulin E binds to, leading to an eventual release of histamine.<ref name=Hunger>Hunger, K., Toxicology and toxicological testing of colorants. Review of Progress in Coloration and Related Topics 2005, 35 (1), 76-89</ref>
Sudan I is also suspected of causing genetic defects. The mutagenicity and genetic hazard have been evaluated with the Ames test and animal experiments. Furthermore, it is suspected of causing cancer. The carcinogenicity was estimated merely through animal testing. It has not been verified in human subjects yet.<ref name=Hunger/>
Safety and regulationEdit
The regulation of Sudan I in Europe started in 2003, after repeated notifications were published in the EU rapid alert system. The EU rapid alert system announced that Sudan I was found in chili powder and other foods that were prepared with it. Due to the suspicion of genotoxicity and mutagenicity of Sudan I, a daily intake was not tolerable. The European Commission therefore prohibited the import of chili and hot chili products.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The German Federal Institute for Risk Assessment was asked its opinion and came to the conclusion that Sudan dyes are harmful to health.Template:Citation needed Sudan I was classified as a category three carcinogen and category three mutagen in Annex I of Directive 67/548/EC. This classification was based on findings from animal experiments from this organisation.Template:Citation needed
The regulation of azo colorants by ‘The EU azo Colorants Directive 2002/61/EC’ has been replaced by the REACH regulation in 2009, when azo dyes were put on the REACH Restriction list Annex XVII.<ref name="cirs">{{#invoke:citation/CS1|citation
|CitationClass=web
}}</ref> This includes that said dyes are forbidden to be used in textiles and leather, that may come in direct and prolonged contact with the skin or oral cavity. No textiles made of leather material are allowed to be coloured with azo dyes, a specific list of which items can be found in the Official Journal of the European Union.<ref name=REACH>Evaluation, Authorisation and Restriction of Chemicals (REACH) as regards Annex XVII. Commission, E., Ed. 2009</ref> Furthermore, it is prohibited, in the European Union, to place any textile or leather articles coloured with azo dyes on the market.<ref name=REACH/>
A certificate for azo dyes exists to ensure that dyes that cleave to one of the forbidden amines are not being used for dyeing. All dyers should ensure that the supply company is fully informed about the legislation of the prohibited azo dyes. To ensure this, they should be members of the ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers) from which they can receive their certificate. Non-ETAD member suppliers will be correlated with doubt about the origin and safety of their dyes. Dyes without certification are not advised to be used.<ref name=cirs/>
Toxicology, genotoxicity, and mutagenesisEdit
HumansEdit
No specific information exists on Sudan I related to the toxic, genotoxic, and mutagenic effect on humans.
Animal experimentsEdit
Sudan I was associated with a significant increase in neoplastic nodules and carcinomas in both male and female rats.<ref>Maronpot, R.; Boorman, G., Interpretation of rodent hepatocellular proliferative alterations and hepatocellular tumors in chemical safety assessment. Toxicologic Pathology 1982, 10 (2), 71-78</ref> Other studies, however, showed no significantly increased incidence of micro-nucleated hepatocytes after the administration of Sudan I. These results suggest that the liver carcinogenicity may not be due to the genotoxic effects of Sudan I. No carcinogenic effects were visible in livers of mice after the application of Sudan I.<ref name="Matsumura"/> But when Sudan I is applied subcutaneously to mice, liver tumors were found.
Furthermore, DNA damage was depicted in the stomach and liver cells of mice.<ref>Tsuda, S.; Matsusaka, N.; Madarame, H.; et al., The comet assay in eight mouse organs: results with 24 azo compounds. Mutation Research/Genetic Toxicology and Environmental Mutagenesis 2000, 465 (1), 11-26</ref> In rats, no significant increase was found in the amount of micro-nucleated epithelial cells of the gastrointestinal tract. This indicates the absence of genotoxic compounds in the gastrointestinal epithelial cells in rats.<ref name="Matsumura"/>
Contradictory to the findings in the gastrointestinal tract and liver, there was an increase in micro-nucleated cells found in the bone marrow. The frequency of micro-nucleated bone marrow cells increased in a dose-dependent manner. Significantly higher frequencies of micro-nucleated immature erythrocytes (MNIME) were found at a dose of 150mg/day or more. This supports the explanation that Sudan I is oxidized or activated by peroxidase in the blood cells, thereby forming micro-nucleated cells.<ref name="Matsumura"/>
Guanosine DNA adducts derived from peroxidase metabolites of Sudan I were also found in vivo, in the bladder of rats. The bladder also contains high levels of tissue peroxidase.<ref name=Stiborova3/>
ToxicologyEdit
Sudan I is genotoxic. It is also carcinogenic in rats.<ref>Template:Cite journal</ref> Comparisons between experimental animals and human Cytochrome P450 (CYP) suggest animal carcinogenicity data may be extrapolated to humans, although the IARC has not done this.<ref name="pmid12384524">Template:Cite journal</ref>
Sudan I is also present as an impurity in Sunset Yellow FCF, which is its desulfonated water-soluble version.
Food scareEdit
In February 2005, Sudan I gained attention, particularly in the United Kingdom. It was identified as a contaminant in Worcestershire sauce produced by Premier Foods. The Food Standards Agency traced the source of the contamination to adulterated chili powder.<ref name="outrage">Template:Cite news</ref>