Hemin (haemin; ferric chloride heme) is an

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

-containing

porphyrin Porphyrins ( ) are heterocyclic, macrocyclic, organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (). In vertebrates, an essential member of the porphyrin group is heme, w ...

with chlorine that can be formed from a

heme Heme (American English), or haem (Commonwealth English, both pronounced /Help:IPA/English, hi:m/ ), is a ring-shaped iron-containing molecule that commonly serves as a Ligand (biochemistry), ligand of various proteins, more notably as a Prostheti ...

group, such as heme B found in the

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

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 sol ...

containing a

ferric In chemistry, iron(III) or ''ferric'' refers to the chemical element, element iron in its +3 oxidation number, oxidation state. ''Ferric chloride'' is an alternative name for iron(III) chloride (). The adjective ''ferrous'' is used instead for i ...

iron (Fe³⁺) ion with a coordinating

chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

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 synt ...

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), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s. It can form inappropriately as a result of

hemolysis Hemolysis or haemolysis (), also known by #Nomenclature, 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 ...

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 aff ...

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 chem ...

Pharmacological use

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

porphyria Porphyria ( or ) is a group of disorders in which substances called porphyrins build up in the body, adversely affecting the skin or nervous system. The types that affect the nervous system are also known as Porphyria#Acute porphyrias, acute p ...

attacks, particularly in

acute intermittent porphyria Acute intermittent porphyria (AIP) is a rare Metabolism, 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 Th ...

. 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 (clotting inside blood vessels) and is then called thrombophlebitis or ...

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, Motility, non-motile, Coccobacillus, coccobacillary, facultative anaerobic organism, facultatively anaerobic, Capnophile, capnophili ...

''.

References

External links

* {{Authority control Porphyrins Orphan drugs