sterol#Types

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

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

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.

Sterols and related compounds play essential roles in the physiology of eukaryotic organisms, and are essential for normal physiology of plants, animals, and fungi. {{Cite journal |last1=Luo |first1=Jie |last2=Yang |first2=Hongyuan |last3=Song |first3=Bao-Liang |date=April 2020 |title=Mechanisms and regulation of cholesterol homeostasis |url=https://www.nature.com/articles/s41580-019-0190-7 |journal=Nature Reviews Molecular Cell Biology |language=en |volume=21 |issue=4 |pages=225–245 |doi=10.1038/s41580-019-0190-7 |pmid=31848472 |s2cid=209392321 |issn=1471-0080|url-access=subscription }} 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. {{cite journal | vauthors = Lampe MA, Burlingame AL, Whitney J, Williams ML, Brown BE, Roitman E, Elias PM | title = Human stratum corneum lipids: characterization and regional variations | journal = Journal of Lipid Research | volume = 24 | issue = 2 | pages = 120–30 | date = February 1983 | pmid = 6833889 | doi = 10.1016/S0022-2275(20)38005-6 | doi-access = free }}

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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. {{cite journal | vauthors = Ostlund RE, Racette SB, Stenson WF | title = Inhibition of cholesterol absorption by phytosterol-replete wheat germ compared with phytosterol-depleted wheat germ | journal = The American Journal of Clinical Nutrition | volume = 77 | issue = 6 | pages = 1385–9 | date = June 2003 | pmid = 12791614 | doi = 10.1093/ajcn/77.6.1385 | doi-access = free }} 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. {{cite journal | date = October–December 2004 | url = http://www.foodcomm.org.uk/17.pdf | archive-url=https://web.archive.org/web/20070915035153mp_/http://www.foodcomm.org.uk/17.pdf | archive-date = 15 September 2007 | title= Do we need to be buying plant sterols? | journal = Food Magazine | volume = 67 | page = 14 | access-date= 8 August 2008 }}

Functional foods enriched with plant sterols/stanols have become the most widely used nonprescription cholesterol-lowering approach.{{Cite journal |last1=Barkas |first1=Fotios |last2=Bathrellou |first2=Eirini |last3=Nomikos |first3=Tzortzis |last4=Panagiotakos |first4=Demosthenes |last5=Liberopoulos |first5=Evangelos |last6=Kontogianni |first6=Meropi D. |date=January 2023 |title=Plant Sterols and Plant Stanols in Cholesterol Management and Cardiovascular Prevention |journal=Nutrients |language=en |volume=15 |issue=13 |pages=2845 |doi=10.3390/nu15132845 |doi-access=free |pmid=37447172 |pmc=10343346 |issn=2072-6643}} Preliminary research has shown that phytosterols may have anticancer effects. {{cite journal | vauthors = Bradford PG, Awad AB | title = Phytosterols as anticancer compounds | journal = Molecular Nutrition & Food Research | volume = 51 | issue = 2 | pages = 161–70 | date = February 2007 | pmid = 17266177 | doi = 10.1002/mnfr.200600164 }}

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Sterols are a subgroup of steroids with a hydroxyl group at the 3-position of the A-ring. {{cite journal | vauthors = Fahy E, Subramaniam S, Brown HA, Glass CK, Merrill AH, Murphy RC, Raetz CR, Russell DW, Seyama Y, Shaw W, Shimizu T, Spener F, van Meer G, VanNieuwenhze MS, White SH, Witztum JL, Dennis EA | display-authors = 6 | title = A comprehensive classification system for lipids | journal = Journal of Lipid Research | volume = 46 | issue = 5 | pages = 839–61 | date = May 2005 | pmid = 15722563 | doi = 10.1194/jlr.E400004-JLR200 | doi-access = free }} 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.

• Cholesterol
• Ergosterol
• Hopanoids
• Hydroxysteroid
• Phytosterol
• Steroids
• Zoosterol

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• {{cite book | vauthors = Alberts B |title=Molecular biology of the cell |publisher=Garland Science |location=New York |year=2002 |page=1874 |volume=IV. Internal Organization of the Cell |chapter=10. Membrane Structure |isbn=978-0-8153-4072-0 |chapter-url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=cholesterol,bilayer&rid=mboc4.section.1864#1874 |quote=The Fluidity of a Lipid Bilayer Depends on Its Composition |chapter-format=Online at NIH}}

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• [http://www.cyberlipid.org/sterols/ster0003.htm Sterols] {{Webarchive|url=https://web.archive.org/web/20100609203913/http://www.cyberlipid.org/sterols/ster0003.htm |date=2010-06-09 }} Cyberlipid.org

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