Sterol is an organic compound with formula C
28O, whose molecule is derived from that of gonane by replacement of a hydrogen atom in position 3 by a hydroxyl group. It is therefore an alcohol of gonane. 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). The most familiar type of animal sterol is cholesterol, which is vital to cell membrane structure, and functions as a precursor to fat-soluble vitamins and steroid hormones.
3D model (JSmol)
|Molar mass||248.410 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Sterols of plants are called phytosterols and sterols of animals are called zoosterols. The most important zoosterol is cholesterol; notable phytosterols include campesterol, sitosterol, and stigmasterol. Ergosterol is a sterol present in the cell membrane of fungi, where it serves a role similar to cholesterol in animal cells.
Role in biochemistryEdit
Sterols and related compounds play essential roles in the physiology of eukaryotic organisms. 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.
Phytosterols as a nutritional supplementEdit
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. 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. Preliminary research has shown that phytosterols may have anticancer effects. 
Chemical classification and structureEdit
Sterols are a subgroup of steroids with a hydroxyl group at the 3-position of the A-ring. 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.
- 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.
- 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. doi:10.1073/pnas.2101276118. PMC 8237579. PMID 34131078.
- 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.
- 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.
- "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.
- 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.
- 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.
- Sterols Cyberlipid.org