# Hematein

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**Hematein** (US spelling) or **haematein** is an oxidized derivative of [haematoxylin](/source/Haematoxylin), used in staining. Haematein should not be confused with [haematin](/source/Haematin), which is a brown to black iron-containing pigment formed by decomposition of [haemoglobin](/source/Haemoglobin). In the Colour Index (but nowhere else), haematein is called haematine.

## Properties

Hematein exhibits indicator-like properties, being blue and less soluble in aqueous [alkaline](/source/Alkalinity) conditions, and red and more soluble in alcoholic [acidic](/source/Acid) conditions. Dissolved haematein slowly reacts with atmospheric [oxygen](/source/Oxygen), yielding products that have not found applications.

## Applications

In acidic solutions, complexes of hematein with metals (usually [aluminium](/source/Aluminium) or [iron](/source/Iron), but also [chromium](/source/Chromium), [zirconium](/source/Zirconium) and several others) are used as biological stains. Aluminium-haematein (haemalum) is the "routine" stain for cell nuclei in sections of human and other animal tissues. Metal-haematein stains are available also for objects other than nuclei, including [myelin sheaths](/source/Myelin_sheath) of nerve fibres and various cytoplasmic [organelles](/source/Organelle). The color of the stained objects depends on the salt used. Aluminium-haematein complexes are usually blue, whereas ferric complexes are very dark blue or black.

Aluminium-haematein complexes (haemalum) bind to the chromatin of the [nuclei](/source/Cell_nucleus) of cells. Although haemalum staining methods have been in use since the 1860s, the chemical identity of the substance or substances that bind the dye-metal complex is still not known with certainty. Some histochemical investigations clearly indicate that a cationic aluminium-haematein complex is attracted to the [phosphate](/source/Phosphate) anions of [DNA](/source/Deoxyribonucleic_acid). Others implicate the [arginine](/source/Arginine) residues of nuclear [histones](/source/Histone) as the substrate of nuclear staining by haemalum.[1]

Structures that stain with aluminium-hematein (haemalum) are often said to be [basophilic](/source/Basophilic), but the staining mechanism is not as simple as for basic (cationic) dyes with smaller molecules. Truly basophilic structures are ones containing [nucleic acids](/source/Nucleic_acid) or other [polyanions](/source/Polyanions) such as glycosaminoglycans of extracellular matrix or acidic [glycoproteins](/source/Glycoprotein) in many types of mucus. As usually used, aluminium-hematein stains only nuclear chromatin and a few other materials such as keratohyalin granules and calcified deposits. Very dilute solutions of aluminium-haematein, used at pH 3.2 (higher than is usual for staining), contain a cationic dye-metal complex and will slowly stain nucleic acids.[2] Haemalum solutions used for routine staining are more concentrated and more acidic (pH 2-2.5) and are able to stain nuclei after chemical or enzymatic extraction of DNA and RNA from the tissue.[3]

## References

1. Puchtler, H., Meloan, S.N., Waldrop, F.S. (1986). "Application of current chemical concepts to metal-haematein and -brazilein stains". *Histochemistry*. **85** (5): 353–364. [doi:10.1007/BF00982665](https://doi.org/10.1007/BF00982665). [PMID 2430916](https://pubmed.ncbi.nlm.nih.gov/2430916). [S2CID 7384777](https://api.semanticscholar.org/CorpusID:7384777)

1. Bettinger, C. & Zimmermann, H.W. (1991). "New investigations on hematoxylin, hematein, and hematein-aluminium complexes. 2. Hematein-aluminium complexes and hemalum staining". *Histochemistry*. **96** (3): 215–228. [doi:10.1007/BF00271540](https://doi.org/10.1007/BF00271540). [PMID 1717413](https://pubmed.ncbi.nlm.nih.gov/1717413). [S2CID 23504301](https://api.semanticscholar.org/CorpusID:23504301)

1. Lillie, R.D., Donaldson, P.T. & Pizzolato, P. (1976). "The effect of graded 60C nitric acid extraction and of deoxyribonuclease digestion on nuclear staining by metachrome mordant dye metal salt mixtures". *Histochemistry*. **46** (4): 297–306. [doi:10.1007/BF02464419](https://doi.org/10.1007/BF02464419). [PMID 57109](https://pubmed.ncbi.nlm.nih.gov/57109). [S2CID 13154258](https://api.semanticscholar.org/CorpusID:13154258)

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Adapted from the Wikipedia article [Hematein](https://en.wikipedia.org/wiki/Hematein) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hematein?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.