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

References_____________________________________________________________________

(1) Chequer FM, Venancio VP, Almeida MR, Aissa AF, Bianchi MLP, Antunes LM. Erythrosine B and quinoline yellow dyes regulate DNA repair gene expression in human HepG2 cells. Toxicol Ind Health. 2017 Oct;33(10):765-774. doi: 10.1177/0748233717715186.

Abstract. Erythrosine B (ErB) is a cherry pink food colorant and is widely used in foods, drugs, and cosmetics. Quinoline yellow (QY) is a chinophthalon derivative used in cosmetic compositions for application to the skin, lips, and/or body surface. Previously, ErB and QY synthetic dyes were found to induce DNA damage in HepG2 cells. The aim of this study was to investigate the molecular basis underlying the genotoxicity attributed to ErB and QY using the RT2 Profiler polymerase chain reaction array and by analyzing the expression profile of 84 genes involved in cell cycle arrest, apoptosis, and DNA repair in HepG2 cells. ErB (70 mg/L) significantly decreased the expression of two genes ( FEN1 and REV1) related to DNA base repair. One gene ( LIG1) was downregulated and 20 genes related to ATR/ATM signaling ( ATR, RBBP8, RAD1, CHEK1, CHEK2, TOPB1), nucleotide excision repair ( ERCC1, XPA), base excision repair ( FEN1, MBD4), mismatch repair ( MLH1, MSH3, TP73), double strand break repair ( BLM), other DNA repair genes ( BRIP1, FANCA, GADD45A, REV1), and apoptosis ( BAX, PPP1R15A) were significantly increased after treatment with QY (20 mg/L). In conclusion, our data suggest that the genotoxic mechanism of ErB and QY dyes involves the modulation of genes related to the DNA repair system and cell cycle.

(2) Poulsen E. Case study: erythrosine. Food Addit Contam. 1993 May-Jun;10(3):315-23. doi: 10.1080/02652039309374154.