Review

Acid Red 51 (CI 45430 or Erythrosine  is a synthetic chemical dye coloured red with iodine. It is labelled with the number E127 in the list of European food additives.

See Erythrosine  

The synthesis process takes place in several stages:

• Preparation of precursors. The main precursors for the synthesis of erythrosine are typically iodine and 2,4,5,7-Tetrabromofluorescein.
• Reaction of precursors. Precursors react together in a solvent suitable for high temperatures. The reaction involves replacing the bromine atoms in the molecule of Tetrabromofluorescein with iodine atoms, forming erythrosine.
• Purification. The reaction mixture is purified to isolate erythrosine with treatments such as crystallization, filtration and drying.

It appears in the form of a red powder.

What it is used for and where

Cosmetics

It is a restricted ingredient IV/80 (CI 45430) a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009 and II/1337 (Acid Red 51; CI 45430) and its aluminium salt (Pigment Red 172 Aluminium lake) when used as a substance in hair dye products.

Cosmetics - INCI Functions

Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Safety

Used in toothpastes and in food, it is considered safe for health if the maximum concentration does not exceed 0.0025% (25 ppm), however, different studies have found that this dye can create problems for human health (1).

It has an effect on the thyroid gland and is considered by the scientific literature to be a secondary tumorigenic agent (2).

Molecular Formula    C₂₀H₆I₄Na₂O₅   C₂₀H₆I₄Na₂O₅H₂O

Molecular Weight 879.86 g/mol

CAS  16423-68-0

Synonyms:

• Erythrosin
• E127
• CI 45430
• Erythrosine
• Erythrosin B
• 2-(2,4,5,7-Tetraiodo-6-hydroxy-3-oxo-3H-xanthene-9-yl)benzoic acid
• Sodium 2',4',5',7'-tetraiodo-3-oxo-3H-spiro[isobenzofuran-1,9'-xanthene]-3',6'-bis(olate)
• 2',4',5',7'-Tetraiodofluorescein, disodium salt
• Disodium 2-(2,4,5,7-tetraiodo-6-oxido-3-oxoxanthen-9-yl)benzoate
• 9-(o-Carboxyphenyl)-6-hydroxy-2,4,5,7-tetraiodo-3H-xanthene-3-one disodium salt monohydrate
• Disodium 9-(O-carboxyphenyl)-6-hydroxy-2,4,5,7-tetraiodo-3H-xanthen-3-one monohydrate
• Disodium 3',6'-dihydroxy-2',4',5',7'-tetraiodospiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one
• C.I.Solvent Red 140
• Erythrosinic acid