Sudan stains and Sudan dyes are synthetic

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s that are used as

dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...

s for various

plastics Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...

(

plastic colorant Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptabil ...

s) and are also used to stain sudanophilic biological samples, usually

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

Sudan II Sudan II (Solvent Orange 7, C.I. 12140, C18H16N2O) is a lysochrome (fat-soluble dye) azo dye used for staining of triglycerides in frozen sections, and some protein bound lipids and lipoproteins on paraffin sections. It has the appearance of red p ...

Sudan III Sudan III is a lysochrome (fat-soluble dye) diazo dye. It is structurally related to azobenzene. Uses It is used to color nonpolar substances such as oils, fats, waxes, greases, various hydrocarbon products, and acrylic emulsions. Its main use ...

Sudan IV Sudan IV (C24H20N4O) is a lysochrome (fat-soluble dye) diazo dye used for the staining of lipids, triglycerides and lipoproteins on frozen paraffin sections. It has the appearance of reddish brown crystals with melting point 199 °C and maximu ...

Oil Red O Oil Red O (Solvent Red 27, Sudan Red 5B, C.I. 26125, C26H24N4O) is a lysochrome (fat-soluble dye) diazo dye used for staining of neutral triglycerides and lipids on frozen sections and some lipoproteins on paraffin sections. It has the appearance ...

, and

Sudan Black B Solvent Black 3 is an azo dye. It is a non-fluorescent, relatively thermostable lysochrome (fat-soluble dye) diazo dye used for Staining (biology), staining of neutral triglycerides and lipids on frozen sections and some lipoproteins on paraffin se ...

are important members of this class of compounds (see images below).

Staining

Sudan dyes have high affinity to fats, therefore they are used to demonstrate

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s, and

lipoprotein A lipoprotein is a biochemical assembly whose primary function is to transport hydrophobic lipid (also known as fat) molecules in water, as in blood plasma or other extracellular fluids. They consist of a triglyceride and cholesterol center, sur ...

s. Alcoholic solutions of Sudan dyes are usually used, however

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

solutions can be used in some situations as well. Sudan stain test is often used to determine the level of

fecal fat In medicine, the fecal fat test is a diagnostic test for fat malabsorption conditions, which lead to excess fat in the feces (steatorrhea). Background In the duodenum, dietary fat (primarily triglycerides) is digested by enzymes such as pancreatic ...

to diagnose

steatorrhea Steatorrhea (or steatorrhoea) is the presence of excess fat in Human feces, feces. Stools may be bulky and difficult to flush, have a pale and oily appearance, and can be especially foul-smelling. An oily anal leakage or some level of fecal incon ...

. A small sample is dissolved in water or saline,

glacial acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

is added to hydrolyze the insoluble salts of

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

s, a few drops of alcoholic solution of Sudan III are added, the sample is spread on a microscopic slide, and heated twice to boil. Normally a stool sample should show only a few drops of red-orange stained fat under the microscope. The method is only semiquantitative but, due to its simplicity, it is used for screening.

Dyeing

Since they are characteristically oil- and fat-soluble, Sudan dyes are also useful for dyeing plastics and fabrics. Sudan dyes I–IV and Sudan Red G consist of arylazo-substituted

2-naphthol 2-Naphthol, or β-naphthol, is a fluorescent colorless (or occasionally yellow) crystalline solid with the formula C10H7OH. It is an isomer of 1-naphthol, differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are ...

s. Such compounds are known to exist as a pair of

tautomer In chemistry, tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the reloca ...

s: :

Examples

File:Sudan I.svg,

Sudan I Sudan I (also known as CI Solvent Yellow 14 or Solvent Orange R) is an organic compound typically classified as an azo dye. It is an orange-red solid, used to color waxes, oils, petrol, solvents, and polishes. Historically, Sudan I used to serve ...

File:Sudan II.svg,

File:Sudan III.svg,

File:Sudan IV.svg,

File:Sudan_Black_B.svg,

File: Sudan Red G.png, Sudan Red G

Safety

Some spices exported from Asia have been adulterated with Sudan dyes, especially

and

, to enhance their colors. This finding has led to controversy because some Sudan dyes are carcinogenic in rats.Larsen, John Chr. "Legal and illegal colors" Trends in Food Science & Technology (2008), 19(Suppl. 1), S60-S65.

References

{{DEFAULTSORT:Sudan Stain Staining Stool tests 2-Naphthols Azo dyes Food colorings IARC Group 3 carcinogens