Amaranth is a chemical compound, an azo synthetic red dye also known by the name Food Red 9 or CI 16185 or Food Red 9

Chemical name:

 trisodium;3-hydroxy-4-[(4-sulfonatonaphthalen-1-yl)diazenyl]naphthalene-2,7-disulfonate

Amaranth is a synthetic monoazo dye known for its bright red color. It is widely used in various industries, including food, cosmetics, and pharmaceuticals, due to its vibrant color and excellent stability.

Chemical Composition and Structure

Amaranth is a monoazo dye, meaning it contains a single azo group (-N=N-) in its molecular structure. The chemical formula for Amaranth is C20H11N2Na3O10S3. Its structure includes an azo group linked to aromatic rings, contributing to its distinctive red hue. It is also known as E123 in the food industry.

Physical Properties

Amaranth typically appears as a reddish-brown powder. It is water-soluble, producing a bright red solution when dissolved. The dye exhibits excellent stability under various conditions, including resistance to light and heat, making it suitable for a wide range of applications.

Chemical Industrial Synthesis Process

• Preparation of reagents. The main raw materials include naphthalene-1,4,5,8-tetrasulfonic acid sodium salt, sulfuric acid (H₂SO₄), sodium nitrite (NaNO₂), a base such as sodium hydroxide (NaOH), and 2-naphthol-3,6-disulfonic acid (J acid).
• Diazotization. The naphthalene-1,4,5,8-tetrasulfonic acid sodium salt is treated with sulfuric acid and sodium nitrite to form a diazonium intermediate. This reaction produces a diazonium salt.
• Coupling. The diazonium salt is then coupled with 2-naphthol-3,6-disulfonic acid (J acid) in the presence of a base, such as sodium hydroxide, to form the azo compound intermediate.
• Formation of Amaranth Dye. The azo compound intermediate is further processed to stabilize the Amaranth dye.
• Filtration. The resulting suspension is filtered to separate the solid precipitate from the aqueous solution.
• Washing. The precipitate is washed with deionized water to remove any soluble impurities.
• Drying. The washed precipitate is dried at controlled temperatures to remove residual moisture and obtain a dry powder.
• Grinding. The dried product is ground to obtain a fine and uniform powder.
• Classification. The dried powder is classified to ensure a uniform particle size. This step may involve sieving or the use of air classifiers.
• Stabilization. The Amaranth powder is stabilized to ensure its stability during transportation and storage, preventing aggregation and degradation.
• Quality control. The Amaranth undergoes rigorous quality testing to ensure it meets standards for purity, color intensity, and safety. These tests include chemical analysis, spectroscopy, and physical tests to determine particle size and rheological properties.

Safety

The problem associated with azo dyes (monoazo or diazo) is photocatalytic degradation leading to eventual oxidation and subsequent formation of impurities such as aromatic amines some of which have carcinogenic activity (1).

Use in hair colouring products is prohibited.

What it is used for and where

Amaranth is a synthetic dye commonly used in a variety of cosmetic and food products. Also known as Acid Red 27 or Erythrosine B, this substance is valued for its intense red hue and is employed to impart color to products such as beverages, sweets, cosmetics, and personal care products.

Cosmetics

It is a restricted ingredient as IV/33 (CI 16185) II/1350 (Acid Red 27; CI 16185: when used as a substance in hair dye products)  a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported: Trisodium 3-hydroxy-4-(4'-sulphonatonaphthylazo)naphthalene-2,7-disulphonate.

Purity criteria as set out in Commission Directive 95/45/EC (E 123)

Colorant. It is an ingredient that makes the final product more attractive from an aesthetic point of view, but can pose a potential health risk with undesirable side effects especially when used continuously as it can be absorbed through the skin or mucous membranes.

Molecular Formula   C₂₀H₁₁N₂Na₃O₁₀S₃     C₂₀H₁₁N₂O₁₀S₃.3Na

CAS  915-67-3

Molecular Weight    604.5 g/mol

 EC number    213-022-2

UNII 37RBV3X49K

DTXSID2021232

Synonyms:

• Food Red 9 
• Acid Red 27
• Amaranth Dye
• AR27 Compound
• FD and C Red No. 2
• Azorubin S
• Red Dye No. 2

References________________________________________________________________________

(1) Chung KT, Stevens SE Jr, Cerniglia CE. The reduction of azo dyes by the intestinal microflora. Crit Rev Microbiol. 1992;18(3):175-90. doi: 10.3109/10408419209114557.

Abstract. Azo dyes are widely used in the textile, printing, paper manufacturing, pharmaceutical, and food industries and also in research laboratories. When these compounds either inadvertently or by design enter the body through ingestion, they are metabolized to aromatic amines by intestinal microorganisms. Reductive enzymes in the liver can also catalyze the reductive cleavage of the azo linkage to produce aromatic amines. However, evidence indicates that the intestinal microbial azoreductase may be more important than the liver enzymes in azo reduction. In this article, we examine the significance of the capacity of intestinal bacteria to reduce azo dyes and the conditions of azo reduction. Many azo dyes, such as Acid Yellow, Amaranth, Azodisalicylate, Chicago Sky Blue, Congo Red, Direct Black 38, Direct Blue 6, Direct Blue 15, Direct Brown 95, Fast Yellow, Lithol Red, Methyl Orange, Methyl Red, Methyl Yellow, Naphthalene Fast Orange 2G, Neoprontosil, New Coccine, Orange II, Phenylazo-2-naphthol, Ponceau 3R, Ponceau SX, Red 2G, Red 10B, Salicylazosulphapyridine, Sunset Yellow, Tartrazine, and Trypan Blue, are included in this article. A wide variety of anaerobic bacteria isolated from caecal or fecal contents from experimental animals and humans have the ability to cleave the azo linkage(s) to produce aromatic amines. Azoreductase(s) catalyze these reactions and have been found to be oxygen sensitive and to require flavins for optimal activity. The azoreductase activity in a variety of intestinal preparations was affected by various dietary factors such as cellulose, proteins, fibers, antibiotics, or supplementation with live cultures of lactobacilli.