Sterol

Type of organic compound

Gonan-3-ol, the simplest sterol

A sterol is any organic compound with a skeleton closely related to cholestan-3-ol. The simplest sterol is gonan-3-ol, which has a formula of C
17H
28O, and is derived from that of gonane by replacement of a hydrogen atom on C3 position by a hydroxyl group. It is therefore an alcohol of gonane.[1][2][3]

More generally, any compounds that contain the gonane structure, additional functional groups, and/or modified ring systems derived from gonane are called steroids. Therefore, sterols are a subgroup of the steroids. They occur naturally in most eukaryotes, including plants, animals, and fungi, and can also be produced by some bacteria (however likely with different functions). [4][5] The most familiar type of animal sterol is cholesterol, which is vital to the structure of the cell membrane, and functions as a precursor to fat-soluble vitamins and steroid hormones. While technically alcohols, sterols are classified by biochemists as lipids (fats in the broader sense of the term).

Some sources make a distinction between sterols and stanols. In this context, the difference between them is analogous to the difference between cholesterol and cholestanol, in that sterols have a double bond between C-5 and C-6, while stanols have not.[6][a]

The gonane skeleton, with the IUPAC recommended numbering of the carbon atoms

## Types

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### Phytosterols

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Phytosterols are sterols naturally found in plants. Notable examples of phytosterols include campesterol, sitosterol, and stigmasterol.

### Zoosterols

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Zoosterols are sterols found in animals. The most significant zoosterol is cholesterol.

### Mycosterols

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Sterols found in fungi are called mycosterols. A common example is ergosterol, a mycosterol present in the cell membrane of fungi, where it serves a role similar to cholesterol in animal cells.

## Role in biochemistry

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Sterols and related compounds play essential roles in the physiology of eukaryotic organisms, and are essential for normal physiology of plants, animals, and fungi. [8] For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as secondary messenger in developmental signaling. In humans and other animals, corticosteroids such as cortisol act as signaling compounds in cellular communication and general metabolism. Sterols are common components of human skin oils. [9]

### Phytosterols as a nutritional supplement

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Main articles: Phytosterol and Phytostanol

Phytosterols, more commonly known as plant sterols, have been shown in clinical trials to block cholesterol absorption sites in the human intestine, thus helping to reduce cholesterol absorption in humans. [10] They are currently approved by the U.S. Food and Drug Administration for use as a food supplement; however, there is some concern that they may block absorption not only of cholesterol, but of other important nutrients as well. At present, the American Heart Association has recommended that supplemental plant sterols be taken only by those diagnosed with elevated cholesterol, and has particularly recommended that they not be taken by pregnant women or nursing mothers. [11] Functional foods enriched with plant sterols/stanols have become the most widely used nonprescription cholesterol-lowering approach.[12] Preliminary research has shown that phytosterols may have anticancer effects. [13]

## Chemical classification and structure

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This section needs expansion. You can help by adding to it. (May 2023)

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Sterols are a subgroup of steroids with a hydroxyl group at the 3-position of the A-ring. [14] They are amphipathic lipids synthesized from acetyl-coenzyme A via the HMG-CoA reductase pathway. The overall molecule is quite flat. The hydroxyl group on the A ring is polar. The rest of the aliphatic chain is non-polar.

## See also

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* Cholesterol
* Ergosterol
* Hopanoids
* Hydroxysteroid
* Phytosterol
* Steroids
* Zoosterol

## References

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1. ^ The word stenol exists to exclusively refer to a sterol with a double bond in the main rings. However, usage of this word is rare outside of compounds such as cholestenol.[7]

1. ^ "sterol (CHEBI:15889)". www.ebi.ac.uk. Retrieved 2023-11-04. – The formula given is C19H31OR, with an R group attached at the sterol sidechain (C-17) position.
2. ^ "Sterols (1107)". pubchem.ncbi.nlm.nih.gov. – This source is more confusing, as it does not indicate an R group and simply uses gonan-3-ol for the structure of sterol. Nevertheless, the text clearly indicates that the name is intended for a larger group of compounds, and at no point is "sterol" intended as a synonym of gonan-3-ol.
3. ^ The International Union of Pure and Applied Chemistry (IUPAC). "IUPAC - sterols (S06006)". goldbook.iupac.org. "Natural products derived from the steroid skeleton and containing a hydroxy group in the 3 position, closely related to cholestan-3-ol."
4. ^ Wei JH, Yin X, Welander PV (24 June 2016). "Sterol Synthesis in Diverse Bacteria". Frontiers in Microbiology. 7: 990. doi:10.3389/fmicb.2016.00990. PMC 4919349. PMID 27446030.
5. ^ Hoshino Y, Gaucher EA (June 2021). "Evolution of bacterial steroid biosynthesis and its impact on eukaryogenesis". Proceedings of the National Academy of Sciences of the United States of America. 118 (25): e2101276118. Bibcode:2021PNAS..11801276H. doi:10.1073/pnas.2101276118. PMC 8237579. PMID 34131078.
6. ^ Cantrill, Richard (2008). "PHYTOSTEROLS, PHYTOSTANOLS AND THEIR ESTERS Chemical and Technical Assessment" (PDF). Food and Agriculture Organization of the United Nations.
7. ^ "stenol, n. meanings, etymology and more". Oxford English Dictionary.
8. ^ Luo, Jie; Yang, Hongyuan; Song, Bao-Liang (April 2020). "Mechanisms and regulation of cholesterol homeostasis". Nature Reviews Molecular Cell Biology. 21 (4): 225–245\. doi:10.1038/s41580-019-0190-7. ISSN 1471-0080. PMID 31848472. S2CID 209392321.
9. ^ Lampe MA, Burlingame AL, Whitney J, Williams ML, Brown BE, Roitman E, Elias PM (February 1983). "Human stratum corneum lipids: characterization and regional variations". Journal of Lipid Research. 24 (2): 120–30\. doi:10.1016/S0022-2275(20)38005-6. PMID 6833889.
10. ^ Ostlund RE, Racette SB, Stenson WF (June 2003). "Inhibition of cholesterol absorption by phytosterol-replete wheat germ compared with phytosterol-depleted wheat germ". The American Journal of Clinical Nutrition. 77 (6): 1385–9\. doi:10.1093/ajcn/77.6.1385. PMID 12791614.
11. ^ "Do we need to be buying plant sterols?" (PDF). Food Magazine. 67: 14. October–December 2004. Archived from the original (PDF) on 15 September 2007. Retrieved 8 August 2008.
12. ^ Barkas, Fotios; Bathrellou, Eirini; Nomikos, Tzortzis; Panagiotakos, Demosthenes; Liberopoulos, Evangelos; Kontogianni, Meropi D. (January 2023). "Plant Sterols and Plant Stanols in Cholesterol Management and Cardiovascular Prevention". Nutrients. 15 (13): 2845. doi:10.3390/nu15132845. ISSN 2072-6643. PMC 10343346. PMID 37447172.
13. ^ Bradford PG, Awad AB (February 2007). "Phytosterols as anticancer compounds". Molecular Nutrition & Food Research. 51 (2): 161–70\. doi:10.1002/mnfr.200600164. PMID 17266177.
14. ^ Fahy E, Subramaniam S, Brown HA, Glass CK, Merrill AH, Murphy RC, et al. (May 2005). "A comprehensive classification system for lipids". Journal of Lipid Research. 46 (5): 839–61\. doi:10.1194/jlr.E400004-JLR200. PMID 15722563.

## Further reading

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* Alberts B (2002). "10. Membrane Structure" (Online at NIH). Molecular biology of the cell. Vol. IV. Internal Organization of the Cell. New York: Garland Science. p. 1874\. ISBN 978-0-8153-4072-0. "The Fluidity of a Lipid Bilayer Depends on Its Composition"

## External links

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* Sterols Archived 2010-06-09 at the Wayback Machine Cyberlipid.org

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Structures of the cell membrane

Membrane lipids|

* Lipid bilayer
* Phospholipids
* Lipoproteins
* Sphingolipids
* Sterols

Membrane proteins|

* Membrane glycoproteins
* Integral membrane proteins/transmembrane protein
* Peripheral membrane protein/Lipid-anchored protein

Other|

* Caveolae/Coated pits
* Cell junctions
* Glycocalyx
* Lipid raft/microdomains
* Membrane contact sites
* Membrane nanotubes
* Myelin sheath
* Nodes of Ranvier
* Nuclear envelope
* Phycobilisomes
* Porosomes

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Cholestanes, membrane lipids: sterols

* Adosterol
* Cholecalciferol/Ergocalciferols
* Cholesterol
* Dihydrotachysterol
* Fusidic acid
* Lanosterol
* Phytosterols

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