View source for Cyclohexane-1,2,3,4,5,6-hexol

{{short description|Family of sugars with a six-carbon ring}}
{{chembox
| Name = Cyclohexane-1,2,3,4,5,6-hexol
| Reference =<ref name=merck11/>
| ImageFile = cis-inositol.svg
| ImageSize = 125px
| ImageCaption = ''cis''-Inositol
| IUPACName = cyclohexane-1,2,3,4,5,6-hexol
| SystematicName = Cyclohexane-1,2,3,4,5,6-hexol
| OtherNames = Inositol
|Section1={{Chembox Identifiers
| IUPHAR_ligand = 4495
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 10239179
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4L6452S749
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 1222251
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D08079
| InChI = 1/C6H12O6/c7-1-2(8)4(10)6(12)5(11)3(1)9/h1-12H/t1-,2-,3-,4+,5-,6-
| InChIKey = CDAISMWEOUEBRE-GPIVLXJGBG
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C6H12O6/c7-1-2(8)4(10)6(12)5(11)3(1)9/h1-12H/t1-,2-,3-,4+,5-,6-
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CDAISMWEOUEBRE-GPIVLXJGSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 87-89-8
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 17268
| SMILES = O[C@@H]1[C@@H](O)[C@H](O)[C@H](O)[C@H](O)[C@H]1O
| PubChem = 892
  }}
|Section2={{Chembox Properties
| C=6 | H=12 | O=6
| MolarMass = 180.16 g/mol
}}
| Section4       = {{Chembox Thermochemistry
| Thermochemistry_ref =
| DeltaGf        = 
| DeltaHc        = 
| DeltaHf        = 
| Entropy        = 
| HeatCapacity   = 
  }}
}}

'''Cyclohexane-1,2,3,4,5,6-hexol''' is a family of [[chemical compound]]s with [[elemental formula|formula]] {{chem2|C6H12O6}}, whose molecule consists of a ring of six [[carbon]] atoms, each bound to one [[hydrogen]] atom and one [[hydroxyl]] group (–OH).  There are nine [[stereoisomer]]s, that differ by the position of the hydroxyl groups relative to the mean plane of the ring. All these compounds are sometimes called '''inositol''', although this name (especially in [[biochemistry]] and related sciences) most often refers to a particular isomer, [[inositol|''myo''-inositol]], which has many important physiological roles and medical uses.

These compounds are classified as [[sugar]]s, specifically [[carbocycle|carbocyclic]] [[sugar]]s or [[sugar alcohol]]s, to distinguish them from the more common [[aldose]]s like [[glucose]].  They generally have sweet taste.<ref name=birc1973/>

These compounds form several [[ester]]s with biochemical and industrial importance, such as [[phytic acid]] and [[phosphatidylinositol phosphate (disambiguation)|phosphatidylinositol phosphate]],

== Isomers and structure ==
The nine stereoisomers of cyclohexane-1,2,3,4,5,6-hexol are distinguished by prefixes: [[inositol|''myo''-]], [[scyllo-inositol|''scyllo'']]-, [[muco-inositol|''muco'']]-, [[1D-chiro-inositol|{{small|D}}-''chiro'']]-, [[L-chiro-inositol|{{small|L}}-''chiro'']]-, [[neo-inositol|''neo''-]], [[allo-inositol|''allo'']]-, [[epi-inositol|''epi'']]-, and [[cis-inositol|''cis''-inositol]].

As their names indicate,  [[1L-chiro-inositol|{{small|L}}]]- and  [[1D-chiro-inositol|{{small|D}}]]-''chiro'' inositol are [[chirality (chemistry)|chiral]], a pair of [[enantiomers]] (mirror-image forms).  All the others are [[meso compound]]s (indistinguishable from their mirror images).<ref name=maju2016/>
:{|
|-
| [[File:myo-inositol.svg|120px]]
| [[File:scyllo-inositol.svg|120px]]
| [[File:muco-inositol.svg|120px]]
|- align=center
| ''myo''-
| ''scyllo''-
| ''muco''-
|-
| [[File:neo-inositol.svg|120px]]
| [[File:allo-inositol.svg|120px]]
| [[File:epi-inositol.svg|120px]]
|- align=center
| ''neo''-
| ''allo''-
| ''epi''-
|-
| [[File:cis-inositol.svg|center|120px]]
| [[File:D-chiro-inositol.svg|120px]]
| [[File:L-chiro-inositol.svg|120px]]
|-
| ''cis''-
| <small>D</small>-''chiro''-
| <small>L</small>-''chiro''-
|}

===Racemate===

The designation ''rac''-''chiro''-inositol has been used for the [[racemic mixture]] (racemate) of equal parts of the two ''chiro'' isomers.   It crystallizes as a single phase, rather than separate D and L crystals, that melts at 250 [[celsius|°C]] (which is 4–5&nbsp;°C higher than the melting point of the pure enantiomers) and decomposes between 308 and 344&nbsp;°C.   The crystal structure is [[monoclinic]] with the <math>P2_1/c</math> [[crystallographic group|group]]. The crystal cell parameters are ''a'' = 1014.35 [[picometre|pm]], ''b'' =  815.42 pm, ''c'' = 862.39 pm, β = 92.3556[[degree (angle)|°]], ''Z'' = 4. The cell volume is 0.71270 [[nanometre|nm]]<sup>3</sup>, or about 0.178&nbsp;nm<sup>3</sup> per molecule (which is a bit smaller than the typical volumes of other isomers).<ref name=beko2014/>

===Ring conformation===

As in [[cyclohexane]], the C6 ring of these compounds can be in two [[cyclohexane conformation|conformations]], "boat" and "chair".  The relative stability of the two forms varies with the isomer, generally favoring the conformation where the hydroxyls are farthest apart from each other.<ref name=brad2005/>

===Melting points===

Some of the stereoisomers crystallize in more than one [[polymorphism (materials science)|polymorph]], with different densities and melting points — which range from 225&nbsp;°C for ''myo''-inositol to about 360&nbsp;°C for polymorph "B" of ''scyllo''-inositol.<ref name=beko2014/>  There is a clear correlation between the melting points and the number and type of chains of hydrogen-bonded hydroxyls.<ref name=simp2006/>

== Biochemistry ==

All isomers except ''allo-'' and ''cis-'' occur in nature, although ''myo''-inositol is substantially more abundant and important than the others.<ref name=sher1968/><ref name=monn2020/>

In humans, ''myo''-inositol is synthesized mostly in the [[kidney]]s, from [[glucose 6-phosphate]].<ref name="part2006"/>  Small amounts of ''myo''-inositol are then converted by a specific [[epimerase]] to {{small|D}}-''chiro''-inositol,<ref name=kian2021/> which is an important messenger molecule in insulin signaling.<ref name=tabr2018/>

A 2020 study found detectable amounts of ''epi''-,  ''neo''-, ''chiro''-, ''scyllo''-, and ''myo''-inositol in the urine of women, pregnant or not.  Concentrations of ''myo'' and ''scyllo'' increased significantly in the third trimester of pregnancy,  with ''scyllo'' varying between 20% and 40% of ''myo''. Concentrations of ''epi'', ''neo'', and ''chiro'' were always a few percent of those of ''myo'', except that ''chiro''- reached 20% of ''myo'' in the second trimester of pregnancy.<ref name=monn2020/>

The bacterium ''[[Bacillus subtilis]]'' can metabolize ''myo''-, ''scyllo''-, and D-''chiro''-inositol.and convert to and from these three isomers.<ref name=yama2011/>

===Phytic acids===

[[File:Phytic acid.svg|alt=2D-structure of phytic acid|thumb|''myo''-Inositol hexakis-dihidrogenphosphate, or phytic acid]]
Plants synthesize inositol hexakis-[[dihydrogenphosphate]], also called [[phytic acid]] or IP6, as a storage of [[phosphorus]]<ref name=phyt2018/>  Inositol penta- (IP5), tetra- (IP4), and triphosphate (IP3) are also called "phytates"

== References ==
<references>

<ref name=merck11>{{cite book|title=Merck Index|edition=11th|page=4883}}</ref>

<ref name=part2006>{{cite book | last1 = Parthasarathy |first1=L. K. |last2=Seelan |first2=R. S. |last3=Tobias |first3=C. |last4=Casanova |first4=M. F. |last5=Parthasarathy |first5=R. N. | title = Mammalian inositol 3-phosphate synthase: its role in the biosynthesis of brain inositol and its clinical use as a psychoactive agent | volume = 39 | pages = 293–314 | year = 2006 | pmid = 17121280 | doi = 10.1007/0-387-27600-9_12 | isbn = 978-0-387-27599-4 |series=Subcellular Biochemistry }}</ref>

<ref name=maju2016>{{Cite book|url=https://books.google.com/books?id=vxoxBbmiLQUC&pg=PA3|title=Biology of Inositols and Phosphoinositides|last1=Majumder|first1=A. L.|last2=Biswas|first2=B. B.  |date=2006-10-03|publisher=Springer Science & Business Media|isbn=9780387276007|language=en}}</ref>

<ref name=kian2021>{{cite journal | vauthors=Kiani AK, Paolacci S, Bertelli M | title=From Myo-inositol to D-chiro-inositol molecular pathways | journal=[[European Review for Medical and Pharmacological Sciences]] | volume=25 | issue=5 | pages=2390–2402 | year=2021 | doi = 10.26355/eurrev_202103_25279 | pmid=33755975}}</ref>

<ref name=brad2005>{{Cite book | url = https://books.google.com/books?id=Af0IyHtGCMUC&pg=PA348 |title=Basic Neurochemistry: Molecular, Cellular and Medical Aspects | last1 = Brady | first1 = S. | last2 = Siegel | first2 = G. | last3 = Albers | first3 = R. W. | last4 = Price | first4 = D. |date=2005 |publisher=Academic Press|isbn=9780080472072|page=348|language=en}}</ref>

<ref name=phyt2018>{{cite web|url=http://www.phytochemicals.info/phytochemicals/phytic-acid.php|title=Phytic acid|website=www.phytochemicals.info|access-date=2018-05-02|url-status=usurped|archive-url=https://web.archive.org/web/20180307183152/http://www.phytochemicals.info/phytochemicals/phytic-acid.php|archive-date=7 March 2018}}</ref>

<ref name=birc1973>G. G. Birch and M. G. Lindley (1973): "Cyclohexane polyols as sweet analogues of the sugars". ''Journal of Food Science'', volume 38, issue 7, pages 1179-1181. {{doi|10.1111/j.1365-2621.1973.tb07232.x}}</ref>

<ref name=beko2014>Sándor L. Bekö, Edith Alig, Martin U. Schmidt, Jacco van de Streek (2014): "On the correlation between hydrogen bonding and melting points in the inositols". ''International Union of Crystallography Journal'' (''IUCrJ''), volume 1, part 1, pages 61-73. {{doi|10.1107/S2052252513026511}}</ref>

<ref name=tabr2018>{{cite journal | vauthors=Tabrizi R, Ostadmohammadi V, Asemi Z | title=The effects of inositol supplementation on lipid profiles among patients with metabolic diseases: a systematic review and meta-analysis of randomized controlled trials | journal=[[Q15756695|Lipids in Health and Disease]] | volume=17 | issue=1 | pages=123 | year=2018 | doi = 10.1186/s12944-018-0779-4 | pmc=5968598 | pmid=29793496 | doi-access=free }}</ref>

<ref name=monn2020>Irina Monnard, Thierry Bénet, Rosemarie Jenni, Sean Austin, Irma Silva-Zolezzi, Jean-Philippe Godin (2020): "Plasma and urinary inositol isomer profiles measured by UHPLC-MS/MS reveal differences in scyllo-inositol levels between non-pregnant and pregnant women". ''Analytical and Bioanalytical Chemistry'', volume 412, pages 7871–7880. {{doi|10.1007/s00216-020-02919-8}}</ref>

<ref name=yama2011>Masaru Yamaoka, Shin Osawa, Tetsuro Morinaga, Shinji Takenaka, Ken-ichi Yoshida (2011): "A cell factory of ''Bacillus subtilis'' engineered for the simple bioconversion of ''myo''-inositol to ''scyllo''-inositol, a potential therapeutic agent for Alzheimer's disease". ''Microbial Cell Factories'', volume 10, article number 69. {{doi|10.1186/1475-2859-10-69}}</ref>

<ref name=sher1968>William R. Sherman, Mark A. Stewart, Mary M. Kurien, Sally L. Goodwin (1968): "The measurement of myo-inositol, myo-inosose-2 and scyllo-inositol in mammalian tissues". ''Biochimica et Biophysica Acta'' (''BBA''), volume 158, issue 2, pages 197-205 {{doi|10.1016/0304-4165(68)90131-1}}</ref>

<ref name=simp2006>Alexandra Simperler, Stephen W. Watt, P. Arnaud Bonnet, William Jones,  W. D. Samuel Motherwell (2006): "Correlation of melting points of inositols with hydrogen bonding patterns". ''CrystEngComm'', volume 8, pages 589-600 {{doi|10.1039/B606107A}}</ref>

</references>

== External links ==
{{Alcohols}}

[[Category:Polyols| ]]
[[Category:Cyclohexanes| ]]
[[Category:Inositol| ]]