AskDefine | Define inositol

Dictionary Definition

inositol n : an optically inactive alcohol that is a component of the vitamin B complex

User Contributed Dictionary

English

Noun

  1. any of several isomeric cyclic polyhydric alcohols, C6H12O6, found in both plant and animal tissue.

Usage notes

Extensive Definition

Inositol, (of which the most prominent naturally occurring form is myo-inositol, cis-1,2,3,5-trans-4,6-cyclohexanehexol), is a carbocyclic polyol that plays an important role as the structural basis for a number of secondary messengers in eukaryotic cells, including inositol phosphates, phosphatidylinositol (PI) and phosphatidylinositol phosphate (PIP) lipids. It is found in many foods, in particular, in cereals with high bran content, nuts, beans, and fruit, especially cantaloupe melons and oranges. Inositol is not considered a vitamin itself because it can be synthesised by the body.
Other naturally occurring isomers (though in minimal quantities) are scyllo-, chiro-, muco-, and neo-inositol. Other possible isomers are allo-, epi-, and cis-inositol.
Myo-Inositol was classified as a member of the vitamin B complex (often referred to as vitamin B8), but was found to be synthesized by the human body (thus, declassifying it as a vitamin).

Structure

The chemical formula of myo-inositol is 6126. In its most stable geometry, the inositol ring is in the chair conformation. There are nine stereoisomers, all of which may be referred to as inositol; however, the natural isomer has a structure in which the 1st, 3rd, 4th, 5th, and 6th hydroxyls are equatorial, whereas the 2nd hydroxyl group is axial.

Synthesis

Myo-Inositol is synthesized from glucose-6-phosphate (G-6-P) in two steps. First, G-6-P is isomerised by ISYNA1 to myo-inositol 1-phosphate, which is then dephosphorylated by IMPase 1 to give free myo-inositol.
1: Eisenberg F Jr, Parthasarathy R. Measurement of biosynthesis of myo-inositol from glucose 6-phosphate. Methods Enzymol. 1987;141:127-43. No abstract available. PMID: 3600356 [PubMed - indexed for MEDLINE]
2: Parthasarathy R, Eisenberg F Jr. The inositol phospholipids: a stereochemical view of biological activity. Biochem J. 1986 Apr 15;235(2):313-22. Review. No abstract available. PMID: 3017301 [PubMed - indexed for MEDLINE]
3.Subcell Biochem. 2006;39:293-314. Mammalian inositol 3-phosphate synthase: its role in the biosynthesis of brain inositol and its clinical use as a psychoactive agent.
Parthasarathy LK, Seelan RS, Tobias C, Casanova MF, Parthasarathy RN. Molecular Neuroscience Laboratory, Autism Research Unit, Mental Health, Behavioral Science and Research Services, VA Medical Center (151), Louisville, Kentucky 40206, USA.
Seelan RS, Parthasarathy LK, Parthasarathy RN. E2F1 regulation of the human myo-inositol 1-phosphate synthase (ISYNA1) gene promoter. Arch Biochem Biophys. 2004 Nov 1;431(1):95-106. PMID: 15464731 [PubMed - indexed for MEDLINE]
5: Parthasarathy LK, Seelan RS, Wilson MA, Vadnal RE, Parthasarathy RN. Regional changes in rat brain inositol monophosphatase 1 (IMPase 1) activity with chronic lithium treatment. Prog Neuropsychopharmacol Biol Psychiatry. 2003 Feb;27(1):55-60. PMID: 12551726 [PubMed - indexed for MEDLINE]
6: Vadnal R, Heng HH, Parthasarathy L, Parthasarathy R. Human chromosomal localization of a gene for inositol monophosphatase by fluorescence in situ hybridization. Neuroreport. 1998 Mar 9;9(4):683-5. PMID: 9559938 [PubMed - indexed for MEDLINE]
7: Parthasarathy R, Parthasarathy L, Vadnal R. Brain inositol monophosphatase identified as a galactose 1-phosphatase. Brain Res. 1997 Dec 5;778(1):99-106. PMID: 9462881 [PubMed - indexed for MEDLINE]
8: Parthasarathy L, Parthasarathy R, Vadnal R. Molecular characterization of coding and untranslated regions of rat cortex lithium-sensitive myo-inositol monophosphatase cDNA. Gene. 1997 May 20;191(1):81-7. PMID: 9210592 [PubMed - indexed for MEDLINE]
9: Vadnal R, Parthasarathy R. Myo-inositol monophosphatase: diverse effects of lithium, carbamazepine, and valproate. Neuropsychopharmacology. 1995 Jul;12(4):277-85. PMID: 7576004 [PubMed - indexed for MEDLINE]
10: Parthasarathy L, Vadnal RE, Parthasarathy R, Devi CS. Biochemical and molecular properties of lithium-sensitive myo-inositol monophosphatase. Life Sci. 1994;54(16):1127-42. Review. PMID: 8152337 [PubMed - indexed for MEDLINE]
11: Parthasarathy L, Vadnal RE, Ramesh TG, Shyamaladevi CS, Parthasarathy R. myo-inositol monophosphatase from rat testes: purification and properties. Arch Biochem Biophys. 1993 Jul;304(1):94-101. PMID: 8391785 [PubMed - indexed for MEDLINE]
12: Parthasarathy R, Parthasarathy L, Ramesh TG, Devi CS, Vadnal RE. The effects of lithium isotopes on the myo-inositol 1-phosphatase reaction in rat brain, liver, and testes. Life Sci. 1992;50(19):1445-50. PMID: 1315412 [PubMed - indexed for MEDLINE]

Function

Inositol as the basis for a number of signalling and secondary messenger molecules, is involved in a number of biological processes, including:

Clinical implications

Psychiatric conditions

Patients suffering from clinical depression generally have decreased levels of inositol in their cerebrospinal fluid.
Some preliminary results of studies on inositol supplements show promising results for people suffering from problems such as bulimia, panic disorder, obsessive-compulsive disorder, and unipolar and bipolar depression. In a double-blind, controlled trial, myo-inositol was superior to fluvoxamine for decreasing the number of panic attacks and had fewer side effects. A double-blind, placebo-controlled study of depressed patients showed that a high dose of inositol (12 grams daily) resulted in significant improvement of symptoms, with no changes noted in liver, kidney, or hematological function. The impetuses for these studies were the observed defects in DCI metabolism in PCOS and the implication of DCI in insulin signal transduction.
Animal studies suggest inositol reduces the severity of the osmotic demyelination syndrome if given prior to rapid correction of chronic hyponatraemia. Further study is required prior to its application in humans for this indication.
Studies from in vitro experiments, animal studies, and limited clinical experiences, claim that inositol may be used effectively against some types of cancer, in particular, when used in combination with phytic acid.

Common use as a "cutting" agent

Inositol is also commonly used as an adulterant(or cutting agent) in many illegal drugs, such as cocaine, methamphetamine, and sometimes heroin.
inositol in Catalan: Inositol
inositol in German: Inosit
inositol in Finnish: Inositoli
inositol in French: Inositol
inositol in Italian: Inositolo
inositol in Dutch: Inositol
inositol in Japanese: イノシトール
inositol in Polish: Inozytol
inositol in Russian: Инозитол
inositol in Swedish: Inositol
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