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 maximum absorption at 520(357) nm.

Sudan IV
Sudan IV.svg
Preferred IUPAC name
Other names
Sudan R, C.I. Solvent Red 24, C.I. 26105, Lipid Crimson, Oil Red, Oil Red BB, Fat Red B, Oil Red IV, Scarlet Red, Scarlet Red N.F, Scarlet Red Scharlach, Scarlet R
  • 85-83-6 ☒N
3D model (JSmol)
  • Interactive image
  • CHEBI:88014 checkY
  • ChEMBL1707454
  • 11252033 checkY
ECHA InfoCard 100.001.487 Edit this at Wikidata
EC Number
  • 201-635-8
  • C19520 checkY
  • 62330
  • I35E9QU96C
  • DTXSID8041743 Edit this at Wikidata
  • InChI=1S/C24H20N4O/c1-16-7-3-6-10-21(16)26-25-19-12-13-22(17(2)15-19)27-28-24-20-9-5-4-8-18(20)11-14-23(24)29/h3-15,29H,1-2H3/b26-25+,28-27+ checkY
  • InChI=1S/C24H20N4O/c1-16-7-3-6-10-21(16)26-25-19-12-13-22(17(2)15-19)27-28-24-20-9-5-4-8-18(20)11-14-23(24)29/h3-15,29H,1-2H3/b26-25+,28-27+
  • Cc4ccccc4/N=N/c3ccc(/N=N/c1c2ccccc2ccc1O)c(C)c3
GHS labelling:
GHS07: Exclamation mark
H315, H319
P264, P280, P302+P352, P305+P351+P338, P321, P332+P313, P337+P313, P362
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sudan IV is one of the dyes used for Sudan staining. Similar dyes include Oil Red O, Sudan III, and Sudan Black B. Staining is an important biochemical technique, offering the ability to visually qualify the presence of the fatty compound of interest without isolating it. For staining purposes, Sudan IV can be made up in propylene glycol.[1] Alternatively, authors have reported using the dye saturated in isopropyl alcohol, 95% ethanol, or 0.05% by weight in acetone:ethanol:water (50:35:15)[citation needed]. The idea is to use a moderately apolar solvent to solubilize the dye allowing it to partition into the highly apolar fat without the solvent solubilizing the fat to be stained.

Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogen by the International Agency for Research on Cancer.[2]

In its purified form it is called Biebrich scarlet R, which should not be confused with the water-soluble Biebrich scarlet.

In industry, it is used to color nonpolar substances like oils, fats, waxes, greases, various hydrocarbon products, and acrylic emulsions. Sudan IV is also used in United Kingdom as a fuel dye to dye lower-taxed heating oil; because of that it is also known as Oil Tax Red. As a food dye, Sudan IV is considered an illegal dye, mainly because of its harmful effect over a long period of time, as it is a carcinogen. It was ruled unsafe in the 1995 food safety regulations report.


  1. ^ "Oil Red O Staining Protocol". IHC World. Retrieved 2021-03-17.
  2. ^ Refat NA, Ibrahim ZS, Moustafa GG, Sakamoto KQ, Ishizuka M, Fujita S (2008). "The induction of cytochrome P450 1A1 by sudan dyes". J. Biochem. Mol. Toxicol. 22 (2): 77–84. doi:10.1002/jbt.20220. PMID 18418879. S2CID 206010951.

External linksEdit

  • Stains File entry