Indigo carmine

This article is about the blue dye derived from indigo. For the unrelated red dye, see Carmine. For other uses, see Carmine (disambiguation).

Indigo carmine
Names
Preferred IUPAC name
Disodium [2(2′)E]-3,3′-dioxo-1,1′,3,3′-tetrahydro[2,2′-biindolylidene]-5,5′-disulfonate
Other names
  • indigotine
  • 5,5′-indigodisulfonic acid sodium salt
  • Brilliant Indigo
  • 4 G
  • C.I. Acid Blue 74
  • C.I. 73015
  • CI Food Blue 1
  • FD&C Blue 2
  • Sicovit Indigotin 85
  • E132
  • indigotindisulfonate sodium
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.011.572 Edit this at Wikidata
EC Number
  • 212-728-8
E number E132 (colours)
KEGG
UNII
  • InChI=1S/C16H10N2O8S2.2Na/c19-15-9-5-7(27(21,22)23)1-3-11(9)17-13(15)14-16(20)10-6-8(28(24,25)26)2-4-12(10)18-14;;/h1-6,17-18H,(H,21,22,23)(H,24,25,26);;/q;2*+1/p-2/b14-13+;; checkY
    Key: KHLVKKOJDHCJMG-QDBORUFSSA-L checkY
  • InChI=1/C16H10N2O8S2.2Na/c19-15-9-5-7(27(21,22)23)1-3-11(9)17-13(15)14-16(20)10-6-8(28(24,25)26)2-4-12(10)18-14;;/h1-6,17-18H,(H,21,22,23)(H,24,25,26);;/q;2*+1/p-2/b14-13+;;
    Key: KHLVKKOJDHCJMG-AKPRSONXBD
  • [Na+].[Na+].[O-]S(=O)(=O)c3cc4C(=O)\C(=C2\C(=O)c1cc(ccc1N2)S([O-])(=O)=O)Nc4cc3
Properties
C16H8N2Na2O8S2
Molar mass 466.36 g/mol
Appearance purple solid
Melting point >300 °C (572 °F)
10 g/L (25 °C (77 °F))
Hazards
GHS labelling:
GHS07: Exclamation mark[1]
Warning
H302[1]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Pharmacology
V04CH02 (WHO)
Legal status
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Indigotindisulfonate sodium
Clinical data
Trade namesBludigo
License data
Identifiers
E numberE132 (colours) Edit this at Wikidata
CompTox Dashboard (EPA)
ECHA InfoCard100.011.572 Edit this at Wikidata

Indigo carmine, or 5,5′-indigodisulfonic acid sodium salt, is an organic salt derived from indigo by aromatic sulfonation, which renders the compound soluble in water. Like indigo, it produces a blue color, and is used in food and other consumables, cosmetics, and as a medical contrast agent and staining agent; it also acts as a pH indicator. It is approved for human consumption in the United States and European Union.[3][4] It has the E number E132, and is named Blue No. 2 by the US Federal Food, Drug, and Cosmetic Act.

Uses

Indigo Carmine (pH indicator)
below pH 11.4 above pH 13.0
11.4 ⇌ 13.0
Experiment using indigo carmine as an indicator

Indigo carmine in a 0.2% aqueous solution is blue at pH 11.4 and yellow at 13.0. Indigo carmine is also a redox indicator, turning yellow upon reduction. Another use is as a dissolved ozone indicator[5] through the conversion to isatin-5-sulfonic acid.[5] This reaction has been shown not to be specific to ozone: it also detects superoxide, an important distinction in cell physiology.[6] It is also used as a dye in the manufacturing of capsules.

Medical uses

Container of indigotindisulfonate sodium for medical use.

Indigotindisulfonate sodium, sold under the brand name Bludigo, is used as a contrast agent during surgical procedures.[2] It is indicated for use in cystoscopy in adults following urological and gynecological procedures.[2][7] It was approved for medical use in the United States in July 2022.[specify][2][7]

In obstetric surgery, it may be used to detect amniotic fluid leaks. In urologic surgery, intravenous indigo carmine can be used to highlight portions of the urinary tract. The dye is filtered rapidly by the kidneys from the blood, and colors the urine blue. However, the dye can cause a potentially dangerous acute increase in blood pressure in some cases.[8]

Indigo carmine stain is not absorbed into cells, so it is applied to tissues to enhance the visibility of mucosa. This leads to its use for examination and diagnosis of benign and malignant lesions and growths on mucosal surfaces of the body.[9]

Food, pharmaceutical, cosmetic, and scientific uses

Indigo carmine is one of the few blue food colorants. Others include the anthocyanidins and rare entites such as variagatic acid and popolohuanone.[10]

Safety and regulation

Indigo carmin shows "genotoxicity, developmental toxicity or modifications of haematological parameters in chronic toxicity studies". Only at 17 mg/kg of body weight per day were effects on testes observed.[11]

References

  1. ^ a b "Indigo carmine". Sigma Aldrich. Retrieved 15 Feb 2022.
  2. ^ a b c d "Bludigo- indigotindisulfonate sodium injection". DailyMed. 7 November 2022. Retrieved 21 January 2023.
  3. ^ Summary of Color Additives for Use in United States in Foods, Drugs, Cosmetics, and Medical Devices, Food and Drug Administration
  4. ^ Current EU approved additives and their E Numbers, Food Standards Agency, 26 November 2010
  5. ^ a b Takeuchi K, Ibusuki T (March 1989). "Quantitative determination of aqueous-phase ozone by chemiluminescence using indigo-5,5'-disulfonate". Analytical Chemistry. 61 (6): 619–623. doi:10.1021/ac00181a025. PMID 2729594.
  6. ^ Kettle AJ, Clark BM, Winterbourn CC (April 2004). "Superoxide converts indigo carmine to isatin sulfonic acid: implications for the hypothesis that neutrophils produce ozone". The Journal of Biological Chemistry. 279 (18): 18521–18525. doi:10.1074/jbc.M400334200. PMID 14978029.
  7. ^ a b "NDA APPROVAL: Bludigo (indigotindisulfonate sodium) injection" (PDF). U.S. Food and Drug Administration. Public Domain This article incorporates text from this source, which is in the public domain.
  8. ^ Craik JD, Khan D, Afifi R (January–February 2009). "The Safety of Intravenous Indigo Carmine to Assess Ureteric Patency During Transvaginal Uterosacral Suspension of the Vaginal Vault". Journal of Pelvic Medicine & Surgery. 15 (1): 11–15. doi:10.1097/SPV.0b013e3181986ace.
  9. ^ Jang JY (November 2015). "The Past, Present, and Future of Image-Enhanced Endoscopy". Clinical Endoscopy. 48 (6): 466–475. doi:10.5946/ce.2015.48.6.466. PMC 4676674. PMID 26668791.
  10. ^ Newsome AG, Culver CA, van Breemen RB (July 2014). "Nature's palette: the search for natural blue colorants". Journal of Agricultural and Food Chemistry. 62 (28): 6498–6511. doi:10.1021/jf501419q. PMID 24930897.
  11. ^ Amchova P, Kotolova H, Ruda-Kucerova J (December 2015). "Health safety issues of synthetic food colorants". Regulatory Toxicology and Pharmacology. 73 (3): 914–922. doi:10.1016/j.yrtph.2015.09.026. PMID 26404013.

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