Hematein
IUPAC name 3,4,6a,10-Tetrahydroxy-6,7-dihydroindeno[2,1-c]chromen-9-one
Identifiers
CAS number	475-25-2
PubChem	10138
UNII	88Q1SYD10B Y
MeSH	Hematein
Jmol-3D images	Image 1
SMILES C1C2=CC(=O)C(=CC2=C3C1(COC4=C3C=CC(=C4O)O)O)O
Properties
Molecular formula	C16H12O6
Molar mass	300.26 g/mol
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hematein (US spelling) or haematein is an oxidized derivative of haematoxylin, used in staining. Haematein must not be confused with haematin, which is a brown to black iron-containing pigment formed by decomposition of haemoglobin. In the Colour Index (but nowhere else), haematein is called haematine, a confusing word that wrongly implies that the compound is an amine.

Hematein exhibits indicator-like properties, being blue and less soluble in aqueous alkaline conditions, and red and more soluble in alcoholic acidic conditions. In acidic conditions, complexes of hematein with metals (usually aluminium or ferric iron) bind to arginine residues of nuclear histones. The color of the stained nuclei depends on the salt used. Aluminium-haematein complexes are usually blue, whereas ferric complexes are very dark blue or black.

Structures that stain with aluminium-hematein (haemalum) are often said to be 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 or other polyanions such as glycosaminoglycans of extracellular matrix or acidic glycoproteins 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 pH3.2 (higher than is usual for staining), contain a cationic dye-metal complex and will slowly stain nucleic acids (Bettinger & Zimmermann 1991). Haemalum solutions used for routine staining are more concentrated and more acidic (pH2-2.5) and are able to stain nuclei after chemical or enzymatic extraction of DNA and RNA from the tissue (Lillie et al., 1976).

References

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• 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: 297-306.
• Bettinger, C. & Zimmermann, H.W. (1991). New investigations on hematoxylin, hematein, and hematein-aluminium complexes. 2. Hematein-aluminium complexes and hemalum staining. Histochemistry 96: 215-228.