Hemin (haemin; ferric chloride heme) is an

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...

-containing

porphyrin Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). The parent of porphyrin is porphine, a rare chemical compo ...

with chlorine that can be formed from a

heme Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consist ...

group, such as heme B found in the

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

of human blood.

Chemistry

Hemin is

protoporphyrin IX Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not solu ...

containing a

ferric In chemistry, iron(III) refers to the element iron in its +3 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe3+. The adjective ferric or the prefix ferri- is often used to sp ...

iron (Fe³⁺) ion with a coordinating

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

ligand. Chemically, hemin differs from the related heme-compound

hematin Haematin (also known as hematin, ferriheme, hematosin, hydroxyhemin, oxyheme, phenodin, or oxyhemochromogen) is a dark bluish or brownish pigment containing iron in the ferric state, obtained by the oxidation of haem. Haematin inhibits the synth ...

chiefly in that the coordinating ion is a chloride ion in hemin, whereas the coordinating ion is a

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...

ion in hematin. The iron ion in haem is ferrous (Fe²⁺), whereas it is ferric (Fe³⁺) in both hemin and hematin. Hemin is endogenously produced in the human body, for example during the turnover of old

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

s. It can form inappropriately as a result of

hemolysis Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo ...

or vascular injury. Several proteins in human blood bind to hemin, such as

hemopexin Hemopexin (or haemopexin; Hpx; Hx), also known as beta-1B-glycoprotein, is a glycoprotein that in humans is encoded by the ''HPX'' gene and belongs to the hemopexin family of proteins. Hemopexin is the plasma protein with the highest binding affi ...

and

serum albumin Serum albumin, often referred to simply as blood albumin, is an albumin (a type of globular protein) found in vertebrate blood. Human serum albumin is encoded by the ''ALB'' gene. Other mammalian forms, such as bovine serum albumin, are chemic ...

Pharmacological use

A lyophilised form of hemin is used as a pharmacological agent in certain cases for the treatment of porphyria attacks, particularly in

acute intermittent porphyria Acute intermittent porphyria (AIP) is a rare metabolic disorder affecting the production of heme resulting from a deficiency of the enzyme porphobilinogen deaminase. It is the most common of the acute porphyrias. Signs and symptoms The clinica ...

. Administration of hemin can reduce heme deficits in such patients, thereby suppressing the activity of delta-amino-levulinic acid synthase (a key enzyme in the synthesis of the porphyrins) by biochemical feedback, which in turn reduces the production of porphyrins and of the toxic precursors of heme. In such pharmacological contexts, hemin is typically formulated with human albumin prior to administration by a medical professional, to reduce the risk of

phlebitis Phlebitis (or Venitis) is inflammation of a vein, usually in the legs. It most commonly occurs in superficial veins. Phlebitis often occurs in conjunction with thrombosis and is then called thrombophlebitis or superficial thrombophlebitis. Unlike ...

and to stabilize the compound, which is potentially reactive if allowed to circulate in free-form. Such pharmacological forms of hemin are sold under a range of trade names including the trademarks Panhematin and Normosang.

History of isolation

Hemin was first crystallized out of blood in 1853, by Ludwik Karol Teichmann. Teichmann discovered that blood pigments can form microscopic crystals. Thus, crystals of hemin are occasionally referred to as 'Teichmann crystals'.

Hans Fischer Hans Fischer (; 27 July 1881 – 31 March 1945) was a German organic chemist and the recipient of the 1930 Nobel Prize for Chemistry "for his researches into the constitution of haemin and chlorophyll and especially for his synthesis of hae ...

synthesized hemin, for which he was awarded the Nobel Prize in Chemistry in 1930. Fischer's procedure involves treating defibrinated blood with a solution of sodium chloride in acetic acid.

Forensics

Hemin can be produced from hemoglobin by the so-called Teichmann test, when hemoglobin is heated with glacial acetic acid (saturated with saline). This can be used to detect blood traces.

Other

Hemin is considered the "X factor" required for the growth of ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...

''.

References

External links

Information
from the American Porphyria Foundation, including emergency delivery information

* {{MeSH name, Hemin Porphyrins Orphan drugs