Carcinogen butter yellow

CAUTION Derivatives of p-dimethylaminoazo benzene (DMAB, butter yellow) are known carcinogens [lb, c]. Other azo compounds, especially aromatic azo compounds, should be handled with great caution. 

The product once was used to color edible fats and therefore was known as Butter Yellow, but its use to color food is prohibited because it is reported to be a potent liver carcinogen for rats. 

Prostaglandin synthetase, peroxidase or lipid peroxidation have been shown to oxidise arylamine xenobiotics to reactive species that bind extensively to DNA. The binding could be an initial event in the toxic or carcinogenic process. Evidence is presented that cation radicals are involved in the formation of the various oxidation products and DNA adduct formation with the carcinogen aminofluorene. Furthermore methylaminoazobenzene (butter yellow) was found to form the same major GSH adduct as is formed in vivo. 

Early in the twentieth century a very hazardous chemical was used as a food colourant 4-dimethylaminoazobenzene, so-called butter yellow , was a yellow azo dye used in some countries to colour butter, before extensive testing was required. When it was studied in 1947, the dye was shown to be a potent carcinogen capable of causing liver tumours in experimental animals, and it was rapidly withdrawn. Fortunately, the treatment of food with additives, which has now become more extensive, is now safe. 

Cows eat fresh, green grass that contains carotene, but they do not metabolize the carotene entirely, and so it ends up in their milk. Butter made from this milk is therefore yellow. In the winter the silage cows eat does not contain carotene because it readily undergoes air oxidation, and the butter made at that time is white. For some time an azo dye called Butter Yellow was added to winter butter to give it the accustomed color, but the dye was found to be a carcinogen. Now winter butter is colored with synthetic carotene, as is all margarine. 

In the United States, Occupational Safety and Health Administration lists butter yellow as a suspected human carcinogen. Human mutation data are also reported. 

Azo Compounds Azo dyes are widely used in the food, pharmaceutical, cosmetic, textile, and leather industry. They are synthetic compounds characterized by one (monoazo) or several intramolecular N = N bonds. Azo dyes, if they are systemically absorbed, can be metabolized by the way of azoreductases of intestinal microflora by liver cells and skin surface bacteria. This metabolism leads to aromatic amines that can be hazardous. In the 1930s, some azo derivatives like 4-dimethyl aminoazoben-zene (Butter Yellow, Cl Solvent Yellow 2, Cl 11020) and o-aminoazotoluene were experimentally found to be directly carcinogenic to liver and bladder after feeding. Other complex azo dyes like Direct Black 38 or Direct Blue 6 (Figure 28) release the aromatic amine benzidine. Some examples of azo dyes metabolized in benzidine and benzidine-congeners are listed in Table 3. 

Butter yellow is a dye once used to color margarine. It has since been shown to be carcinogenic, and its use in food is no longer permitted. Outline a synthesis of butter yellow from benzene and W,W-dimethylaniline. 

Azo dyes find use as acid-base indicators. For example. Methyl Red prepared in this experiment. Methyl Orange, and Congo Red are well-known acid-base indicators. Azo dyes are commonly used in the textile, food, and cosmetic industries FD C Yellow No. 6, a yellow azo dye is used to color candy, ice cream, beverages, and so on. Several azo dyes (including Butter Yellow and FD C Red No. 2) have been banned by the FDA from use in foods, drugs, and cosmetics in the United States because of suspected carcinogenic properties. 

A yellow azo dye once used to color margarine has been outlawed because it is carcinogenic. Outline a synthesis of this dye, butter yellow, starting from benzene and N,N-dimethylaniline ... 

When margarine was first produced, it was colored with butter yellow to make it look more like butter. (White margarine would not be very appetizing.) This dye was abandoned after it was found to be carcinogenic. j8-Carotene (page 635) is now used to color margarine. Methyl orange is a commonly used acid-base indicator (see Problem 71). 

The carcinogenic action of butter yellow (4-dimethylaminoazobenzene) is thought to depend on N-hydroxylation of the corresponding monomethyl analogue (which arises by bio-demethylation) (Poirier et al.y 1967). 

---