| Revision as of 11:36, 12 November 2010 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Script assisted update of identifiers from ChemSpider, CommonChemistry and FDA for the Chem/Drugbox validation project - Updated: StdInChI StdInChIKey.← Previous edit |
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{{lowercase title}} |
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{{chembox |
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{{chembox |
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| Verifiedfields = changed |
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| verifiedrevid = 387889736 |
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| Watchedfields = changed |
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| Name=β-Sitosterol |
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| verifiedrevid = 396299902 |
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| Name =β-Sitosterol |
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| ImageFile = Sitosterol structure.svg |
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| ImageFile = Sitosterol structure.svg |
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| ImageSize = 200px |
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| ImageSize = 240 |
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| ImageAlt = Skeletal formula of sitosterol |
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| IUPACName = 17-(5-Ethyl-6-methylheptan-2-yl)-10,13-dimethyl-2,3,4,7,8,9,11,12,14,15,16,17-dodecahydro-1''H''-cyclopentaphenanthren-3-ol |
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| ImageFile1 = Sitosterol-3D-balls.png |
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| OtherNames = 22,23-Dihydrostigmasterol, Stigmast-5-en-3-ol, β-Sitosterin |
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| ImageSize1 = 250 |
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| Section1 = {{Chembox Identifiers |
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| ImageAlt1 = Ball-and-stick model of the sitosterol molecule |
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| ChemSpiderID = 192962 |
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| IUPACName = Stigmast-5-en-3β-ol |
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| SystematicName = (1''R'',3a''S'',3b''S'',7''S'',9a''R'',9b''S'',11a''R'')-1--9a,11a-dimethyl-2,3,3a,3b,4,6,7,8,9,9a,9b,10,11,11a-tetradecahydro-1''H''-cyclopentaphenanthren-7-ol |
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| OtherNames = 22,23-Dihydrostigmasterol, β-Sitosterin |
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|Section1={{Chembox Identifiers |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 192962 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = S347WMO6M4 |
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| UNII = S347WMO6M4 |
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| ChEMBL_Ref = {{ebicite|changed|EBI}} |
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| ChEMBL = 221542 |
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| InChI = 1/C29H50O/c1-7-21(19(2)3)9-8-20(4)25-12-13-26-24-11-10-22-18-23(30)14-16-28(22,5)27(24)15-17-29(25,26)6/h10,19-21,23-27,30H,7-9,11-18H2,1-6H3/t20-,21-,23+,24+,25-,26+,27+,28+,29-/m1/s1 |
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| InChI = 1/C29H50O/c1-7-21(19(2)3)9-8-20(4)25-12-13-26-24-11-10-22-18-23(30)14-16-28(22,5)27(24)15-17-29(25,26)6/h10,19-21,23-27,30H,7-9,11-18H2,1-6H3/t20-,21-,23+,24+,25-,26+,27+,28+,29-/m1/s1 |
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| InChIKey = KZJWDPNRJALLNS-VJSFXXLFBZ |
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| InChIKey = KZJWDPNRJALLNS-VJSFXXLFBZ |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI = 1S/C29H50O/c1-7-21(19(2)3)9-8-20(4)25-12-13-26-24-11-10-22-18-23(30)14-16-28(22,5)27(24)15-17-29(25,26)6/h10,19-21,23-27,30H,7-9,11-18H2,1-6H3/t20-,21-,23+,24+,25-,26+,27+,28+,29-/m1/s1 |
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| StdInChI = 1S/C29H50O/c1-7-21(19(2)3)9-8-20(4)25-12-13-26-24-11-10-22-18-23(30)14-16-28(22,5)27(24)15-17-29(25,26)6/h10,19-21,23-27,30H,7-9,11-18H2,1-6H3/t20-,21-,23+,24+,25-,26+,27+,28+,29-/m1/s1 |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = KZJWDPNRJALLNS-VJSFXXLFSA-N |
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| StdInChIKey = KZJWDPNRJALLNS-VJSFXXLFSA-N |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = 83-46-5 |
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| CASNo = 83-46-5 |
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| PubChem = 222284 |
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| PubChem = 222284 |
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| ChEBI_Ref = {{ebicite|changed|EBI}} |
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| SMILES = O4C/C3=C/C1(CC2(1CC2(C)CC(CC)C(C)C)C)3(C)CC4 |
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| ChEBI = 27693 |
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| MeSHName = |
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| SMILES = O4C/C3=C/C1(CC2(1CC2(C)CC(CC)C(C)C)C)3(C)CC4 |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| C=29|H=50|O=1 |
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| C=29 | H=50 | O=1 |
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| Appearance = |
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| Appearance = |
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| Density = |
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| Density = |
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| MeltingPtC = 136 to 140 |
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| MeltingPt = 136-140 °C<ref>1. Vahur Oja et. al., “Sublimation Thermodynamic Parameters for Cholesterol, Ergosterol, β-Sitosterol, and Stigmasterol,” Journal of Chemical & Engineering Data 54, no. 3 (March 12, 2009): 730-734, doi:10.1021/je800395m. |
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| MeltingPt_ref = <ref>{{cite journal| year = 2009 | title = Sublimation Thermodynamic Parameters for Cholesterol, Ergosterol, β-Sitosterol, and Stigmasterol | journal = Journal of Chemical & Engineering Data | volume = 54 | issue = 3| pages = 730–734 | doi = 10.1021/je800395m| last1 = Oja| first1 = Vahur| last2 = Chen| first2 = Xu| last3 = Hajaligol| first3 = Mohammad R.| last4 = Chan| first4 = W. Geoffrey }}</ref> |
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</ref> |
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| Section3 = {{Chembox Hazards |
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| Solubility = |
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|Section3={{Chembox Hazards |
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'''β-Sitosterol''' is one of several ]s (plant sterols) with ]s similar to that of ]. Sitosterols are white, waxy powders with a characteristic odor. They are hydrophobic and soluble in alcohols. |
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'''β-Sitosterol''' (''beta''-sitosterol) is one of several ]s (plant sterols) with ]s similar to that of ]. It is a white, waxy powder with a characteristic odor, and is one of the components of the ] ]. Phytosterols are hydrophobic and soluble in alcohols. |
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==Natural occurrences and food== |
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==Sources== |
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β-Sitosterol is widely distributed in the ]. It is found in ], ], ]s, and derived prepared foods such as ]s.<ref>{{cite web|url=http://nutritiondata.self.com/foods-000077000000000000000.html|publisher=Conde Nast, USDA National Nutrient Database, version SR-21|title=Nutrition data: Foods highest in beta-sitosterol per 200 calorie serving|date=2014|access-date=25 September 2015|archive-date=26 September 2015|archive-url=https://web.archive.org/web/20150926020129/http://nutritiondata.self.com/foods-000077000000000000000.html|url-status=live}}</ref> ], a species of marine annelid, predominantly incorporate β-sitosterol into their cell membranes instead of cholesterol, though cholesterol is also present in said membranes.<ref name=":0">{{cite journal |last1=Michellod |first1=Dolma |last2=Bien |first2=Tanja |last3=Birgel |first3=Daniel |last4=Violette |first4=Marlene |last5=Kleiner |first5=Manuel |last6=Fearn |first6=Sarah |last7=Zeidler |first7=Caroline |last8=Gruber-Vodicka |first8=Harald R. |last9=Dubilier |first9=Nicole |last10=Liebeke |first10=Manuel |title=De novo phytosterol synthesis in animals |journal=Science |date=5 May 2023 |volume=380 |issue=6644 |pages=520–526 |doi=10.1126/science.add7830 |pmid=37141360 |bibcode=2023Sci...380..520M |s2cid=248367784 |language=en |issn=0036-8075 |pmc=11139496 }}</ref> |
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==Human research== |
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It is widely distributed in the ] and found in '']'', pecans, '']'' (saw palmetto), avocados, '']'' (]), '']'', ] fruit, ], ], ]s, ]s, ], ], and '']''. |
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β-Sitosterol is being studied for its potential to reduce ] (BPH)<ref name=CR_2000>{{Cite journal | pmid = 10796740 | year = 2000 | last1 = Wilt | first1 = T | journal = The Cochrane Database of Systematic Reviews | issue = 2 | pages = CD001043 | last2 = Ishani | first2 = A | last3 = MacDonald | first3 = R | last4 = Stark | first4 = G | last5 = Mulrow | first5 = C | last6 = Lau | first6 = J | doi = 10.1002/14651858.CD001043 | title = Beta-sitosterols for benign prostatic hyperplasia| volume = 2011 | pmc = 8407049 }}</ref><ref name=Kim_2012>{{Cite journal | pmid = 22883375 | year = 2012 | last1 = Kim | first1 = T. H. | title = Dietary supplements for benign prostatic hyperplasia: An overview of systematic reviews | journal = Maturitas | volume = 73 | issue = 3 | pages = 180–5 | last2 = Lim | first2 = H. J. | last3 = Kim | first3 = M. S. | last4 = Lee | first4 = M. S. | doi = 10.1016/j.maturitas.2012.07.007}}</ref> and blood ] levels.<ref>{{cite journal|journal=J Am Coll Nutr|year=2008|volume=27|issue=5|pages=588–95|title=Cholesterol-lowering efficacy of plant sterols in low-fat yogurt consumed as a snack or with a meal|vauthors=Rudkowska I, AbuMweis SS, Nicolle C, Jones PJ|pmid=18845709|doi=10.1080/07315724.2008.10719742|s2cid=25733066}}</ref> |
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==Genetic disorder== |
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==Uses== |
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While plant sterols are usually beneficial, there is a rare autosomal recessive genetic disorder ] which causes over-absorption of phytosterols.<ref>{{cite journal |author1=Patel Manoj D. |author2=Thompson Paul D. | year = 2006 | title = Phytosterols and Vascular Disease | journal = Atherosclerosis | volume = 186 | issue = 1| pages = 12–19 | doi = 10.1016/j.atherosclerosis.2005.10.026 | pmid = 16325823 }}</ref> |
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Alone and in combination with similar phytosterols, β-sitosterol reduces ] levels of ], and is sometimes used in treating ]. β-Sitosterol inhibits cholesterol absorption in the intestine.<ref>Matsuoka, K.; Nakazawa, T.; Nakamura, A.; Honda, C.; Endo, K.; Tsukada, M. Study of Thermodynamic Parameters for Solubilization of Plant Sterol and Stanol in Bile Salt Micelles. Chem. Phys. Lipids 2008, 154, 87-93.</ref> When the sterol is absorbed in the intestine, it is transported by lipoproteins and incorporated into the cellular membrane.<ref>Awad, A. B.; Fink, C. S. Phytosterols as Anticancer Dietary Components: Evidence and Mechanism of Action. J. Nutr. 2000, 130, 2127-2130.</ref> Phytosterols and phytostanols both inhibit the uptake of dietary and biliary cholesterol, decreasing the levels of LDL and serum total cholesterol. Because the structure of β-sitosterol is very similar to that of cholesterol, β-sitosterol takes the place of dietary and biliary cholesterol in micelles produced in the intestinal lumen.<ref>Moreau, R. A.; Whitaker, B. D.; Hicks, K. B. Phytosterols, Phytostanols, and Their Conjugates in Foods: Structural Diversity, Quantitative Analysis, and Health-Promoting Uses. Prog. Lipid Res. 2002, 41, 457-500.</ref> This causes less cholesterol absorption in the body. |
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==Precursor of anabolic steroid boldenone== |
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One small study shows a positive effect on male hair loss in combination with ].<ref>{{cite journal |author=Prager N, Bickett K, French N, Marcovici G |title=A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia |journal=Journal of alternative and complementary medicine (New York, N.Y.) |volume=8 |issue=2 |pages=143–52 |year=2002 |pmid=12006122 |doi=10.1089/107555302317371433}}</ref> |
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Being a steroid, β-sitosterol is a precursor of anabolic steroid ]. ] is commonly used in veterinary medicine to induce growth in cattle but it is also one of the most commonly abused anabolic steroids in sports. This led to suspicion that some athletes testing positive on boldenone undecylenate did not actually abuse the hormone itself but consumed food rich in β-sitosterol.<ref>{{cite journal | title = Boldenone, Boldione, and Milk Replacers in the Diet of Veal Calves: The Effects of Phytosterol Content on the Urinary Excretion of Boldenone Metabolites |author1=G. Gallina |author2=G. Ferretti |author3=R. Merlanti |author4=C. Civitareale |author5=F. Capolongo |author6=R. Draisci |author7=C. Montesissa | journal = J. Agric. Food Chem. | year = 2007 | volume = 55 | pages = 8275–8283 | doi = 10.1021/jf071097c | issue = 20 | pmid=17844992}}</ref><ref>{{cite journal | journal = Food Addit. Contam. | year = 2007 | volume = 24 | issue = 7 | pages = 679–84 | title = Phytosterol consumption and the anabolic steroid boldenone in humans: a hypothesis piloted | vauthors = Ros MM, Sterk SS, Verhagen H, Stalenhoef AF, de Jong N | doi = 10.1080/02652030701216727 | pmid = 17613052 | s2cid = 38614535 | url = https://hal.archives-ouvertes.fr/hal-00577549/file/PEER_stage2_10.1080%252F02652030701216727.pdf | access-date = 2019-07-06 | archive-date = 2020-10-03 | archive-url = https://web.archive.org/web/20201003011822/https://hal.archives-ouvertes.fr/hal-00577549/file/PEER_stage2_10.1080%252F02652030701216727.pdf | url-status = live }}</ref><ref>{{cite journal | title = Excretion profile of boldenone in urine of veal calves fed two different milk replacers |author1=R. Draisci |author2=R. Merlanti |author3=G. Ferretti |author4=L. Fantozzi |author5=C. Ferranti |author6=F. Capolongo |author7=S. Segato |author8=C. Montesissa | journal = Analytica Chimica Acta | volume = 586 | issue = 1–2 | year = 2007 | pages = 171–176 | doi = 10.1016/j.aca.2007.01.026 | pmid = 17386709|bibcode=2007AcAC..586..171D }}</ref> |
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==Chemistry== |
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In Europe, β-sitosterol plays a major role in ] especially in the treatment of ] (BPH).{{Fact|date=February 2008}} |
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===Chemical engineering=== |
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It is also used in Europe for the treatment of prostatic carcinoma<ref>.Accessed: 12-19-2008.</ref> and breast cancer,<ref>. Accessed 12-19-2008.</ref> although the benefits are still being evaluated in the US. |
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The use of β-sitosterol as a chemical intermediate was for many years limited due to the lack of a chemical point of attack on the side-chain that would permit its removal. Extensive efforts on the part of many laboratories eventually led to the discovery of a ] ] that efficiently effected that transformation. Fermentation digests the entire aliphatic side-chain at carbon 17 to afford a mixture of 17-keto products including ].<ref>Lenz, G. R.; Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, London, 1983, Vol. 21, 645.</ref> |
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===Synthesis=== |
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While plant sterols are beneficial, phytosterolemia, a rare autosomal recessive genetic disorder, can occur due to over-absorption of phytosterols.<ref>Patel Manoj, D.; Thompson Paul, D. Phytosterols and Vascular Disease. Atherosclerosis 2006, 186, 12-19.</ref> Phytosterols accumulate and are over-absorbed in tissue, which causes premature coronary artery disease and tendon xanthoma. |
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Total synthesis of β-sitosterol has not been achieved. However, β-sitosterol has been synthesized from stigmasterol '''1''', which involves a specific hydrogenation of the side-chain of stigmasterol. |
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The first step in the synthesis forms stigmasterol tosylate '''2''' from stigmasterol '''1''' (95% purity) using p-TsCl, DMAP, and pyridine (90% yield). The tosylate '''2''' then undergoes solvolysis as it is treated with pyridine and anhydrous MeOH to give a 5:1 ratio of i-stigmasterol methyl ether '''3''' (74% yield) to stigmasterol methyl ether '''4''', which is subsequently removed by chromatography. The hydrogenation step of a previously proposed synthesis involved the catalyst Pd/C and the solvent ethyl acetate. However, due to isomerisation during hydrolysis, other catalysts, such as PtO<sub>2</sub>, and solvents, such as ethanol, were tested. There was little change with the use of a different catalyst. Ethanol, however, prevented isomerisation and the formation of the unidentified impurity to give compound '''5'''. The last step of the synthesis is deprotection of the β-ring double bond of '''5''' with p-TsOH, aqueous dioxane, and heat (80 °C) to yield β-sitosterol '''6'''. The cumulative yield for the final two steps was 55%, and the total yield for the synthesis was 37%.<ref>{{Cite journal|pmid= 16186940|year= 2005|last1= McCarthy|first1= FO|last2= Chopra|first2= J|last3= Ford|first3= A|last4= Hogan|first4= SA|last5= Kerry|first5= JP|last6= O'Brien|first6= NM|last7= Ryan|first7= E|last8= Maguire|first8= AR|title= Synthesis, isolation and characterisation of beta-sitosterol and beta-sitosterol oxide derivatives|volume= 3|issue= 16|pages= 3059–65|doi= 10.1039/b505069c|journal= Organic & Biomolecular Chemistry}}</ref> |
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The use of sitosterol as a chemical intermediate was for many years limited due to the lack of a chemical point of attack on the side-chain that would permit its removal. Extensive efforts on the part of many laboratories eventually led to the discovery of a ] ] that efficiently effected that transformation. Fermentation digests the entire aliphatic side-chain at carbon 17 to afford a mixture of 17-keto products including ].<ref>Lenz, G. R.; Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, London, 1983, Vol. 21, 645.</ref> |
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== Synthesis == |
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Total synthesis of β-sitosterol has not been achieved. However, β-sitosterol has been synthesized from stigmasterol '''1''', which involves a specific hydrogenation of the side-chain of stigmasterol (See Figure Below). The first step in the synthesis forms stigmasterol tosylate '''2''' from stigmasterol '''1''' (95% purity) using p-TsCl, DMAP, and pyridine (90% yield). The tosylate '''2''' then undergoes solvolysis as it is treated with pyridine and anhydrous MeOH to give a 5:1 ratio of i-stigmasterol methyl ether '''3''' (74% yield) to stigmasterol methyl ether '''4''', which is subsequently removed by chromatography. The hydrogenation step of a previously proposed synthesis involved the catalyst Pd/C and the solvent ethyl acetate. However, due to isomerisation during hydrolysis, other catalysts, such as PtO2, and solvents, such as ethanol, were tested. There was little change with the use of a different catalyst. Ethanol, however, prevented isomerisation and the formation of the unidentified impurity to give compound '''5'''. The last step of the synthesis is deprotection of the β-ring double bond of '''5''' with p-TsOH, aqueous dioxane, and heat (80 °C) to yield β-sitosterol '''6'''. The cumulative yield for the final two steps was 55%, and the total yield for the synthesis was 37%.<ref>McCarthy, F. O.; Chopra, J.; Ford, A.; Hogan, S. A.; Kerry, J. P.; O'Brien, N. M.; Ryan, E.; Maguire, A. R. Synthesis, Isolation and Characterization of β-Sitosterol and β-Sitosterol Oxide Derivatives. Org. Biomol. Chem. 2005, 3, 3059-3065.</ref> |
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== Biosynthesis == |
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==Biosynthesis== |
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The regulation of the biosynthesis of both sterols and some specific lipids occurs during membrane biogenesis.<ref>Hartmann, M.-A. Sterol Metabolism and Functions in Higher Plants. Top. Curr. Genet. 2004, 6, 183-211.</ref> Through 13C-labeling patterns, it has been determined that both the mevalonate and deoxyxylulose pathways are involved in the formation of β-sitosterol.<ref>De-Eknamkul, W.; Potduang, B. Biosynthesis of β-Sitosterol and Stigmasterol in Croton sublyratus Proceeds Via a Mixed Origin of Isoprene Units. Phytochemistry 2003, 62, 389-398.</ref> The precise mechanism of β-sitosterol formation varies according to the organism, but is generally found to come from cycloartenol.<ref>Dewick, P. M. Medicinal Natural Products: A Biosynthetic Approach. 3 ed.; John Wiley & Sons Ltd.: United Kingdom cyclization, 2009; p 539.</ref> |
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The regulation of the biosynthesis of both sterols and some specific lipids occurs during membrane biogenesis.<ref>{{Cite book |doi=10.1007/978-3-540-40999-1_6|chapter=5 Sterol metabolism and functions in higher plants|title=Lipid Metabolism and Membrane Biogenesis|series=Topics in Current Genetics|year=2003|last1=Hartmann|first1=Marie-Andrée|isbn=978-3-540-20752-8|volume=6|pages=183–211}}</ref> Through 13C-labeling patterns, it has been determined that both the mevalonate and deoxyxylulose pathways are involved in the formation of β-sitosterol.<ref>{{cite journal |author1=De-Eknamkul W. |author2=Potduang B. | year = 2003 | title = Biosynthesis of β-Sitosterol and Stigmasterol in Croton sublyratus Proceeds Via a Mixed Origin of Isoprene Units | journal = Phytochemistry | volume = 62 | issue = 3| pages = 389–398 | doi = 10.1016/S0031-9422(02)00555-1 | pmid = 12620352 |bibcode=2003PChem..62..389D }}</ref> The precise mechanism of β-sitosterol formation varies according to the organism, but is generally found to come from ].<ref>Dewick, P. M. Medicinal Natural Products: A Biosynthetic Approach. 3 ed.; John Wiley & Sons Ltd.: United Kingdom cyclization, 2009; p 539.</ref> |
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The biosynthesis of cycloartenol begins as one molecule of isopentenyl diphosphate (IPP) and two molecules of dimethylallyl diphosphate (DMAPP) form farnesyl diphosphate (FPP). Two molecules of FPP are then joined tail-to-tail to yield squalene, a triterpene. Squalene, through a cyclization reaction with 2,3-oxidosqualene 6 as an intermediate forms cycloartenol. The biosynthesis of β-sitosterol from cycloartenol is summarized below. The double bond of cycloartenol is methylated by SAM to give a carbocation that undergoes a hydride shift and loses a proton to yield a compound with a methylene side-chain. Both of these steps are catalyzed by sterol C-24 methyltransferase (E1). Compound 8 is then catalyzed by sterol C-4 demethylase (E2) and loses a methyl group to produce cycloeucalenol. Subsequent to this, the cyclopropane ring is opened with cycloeucalenol cycloisomerase (E3) to form '''10'''. Compound '''10''' loses a methyl group and undergoes an allylic isomerization to form Gramisterol '''11'''. This step is catalyzed by sterol C-14 demethylase (E4), sterol Δ14-reductase (E5), and sterol Δ8-Δ7-isomerase (E6). The last methyl group is removed by sterol demethylase (E7) to form episterol '''12'''. Episterol '''12''' is methylated by SAM to produce a second carbocation, which loses a proton to yield '''13'''. This step is catalyzed by 24-methylenesterol C-methyltransferase (E8). Compound '''13''' now undergoes reduction by NADPH and modifications in the β-ring to form β-sitosterol. |
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The biosynthesis of cycloartenol begins as one molecule of ] (IPP) and two molecules of ] (DMAPP) form ] (FPP). Two molecules of FPP are then joined tail-to-tail to yield ], a ]. Squalene, through a cyclization reaction with 2,3-oxidosqualene 6 as an intermediate forms cycloartenol. |
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The double bond of cycloartenol (compound 7 in diagram) is methylated by SAM to give a carbocation that undergoes a hydride shift and loses a proton to yield a compound with a methylene side-chain. Both of these steps are catalyzed by sterol C-24 methyltransferase (Step E1 in diagram). Compound 8 is then catalyzed by sterol C-4 demethylase (E2) and loses a methyl group to produce cycloeucalenol. Subsequent to this, the cyclopropane ring is opened with cycloeucalenol cycloisomerase (E3) to form '''10'''. Compound '''10''' loses a methyl group and undergoes an allylic isomerization to form gramisterol '''11'''. This step is catalyzed by sterol C-14 demethylase (E4), sterol Δ14-reductase (E5), and sterol Δ8-Δ7-isomerase (E6). The last methyl group is removed by sterol demethylase (E7) to form episterol '''12'''. Episterol '''12''' is methylated by SAM to produce a second carbocation, which loses a proton to yield '''13'''. This step is catalyzed by 24-methylenesterol C-methyltransferase (E8). Compound '''13''' now undergoes reduction by NADPH and modifications in the β-ring to form β-sitosterol. An alternative pathway is described for phytosterol synthesis in some animals, a key enzyme responsible is the sterolmethyltransferase (SMT).<ref name=":0" /> |
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==Side-Effects== |
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Numerous clinical studies and trials of β-sitosterol have shown that it may cause side-effects, most of which are not usually dangerous. By taking more than the recommended dose, people may suffer from stomach upset, ], ], gas or ], impotence (also known as ] or ED), decreased sex drive.<ref>{{cite article |
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|author=Kristi Monson, PharmD; Arthur Schoenstadt, MD |
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|title=Beta-Sitosterol Side Effects |
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|year=2008 |
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|month=February |
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|issue=1 |
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|doi= |
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|url=http://prostate.emedtv.com/beta-sitosterol/beta-sitosterol-side-effects.html |
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}}</ref> |
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The latter side-effects of beta-sitosterol can be explained by through its effects on male hormones, especially ] and ] (DHT).<ref>{{cite journal |
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|author=Selvarajah D, Gandhi R, Emery CJ, Tesfaye S. |
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|title=Randomized placebo-controlled double-blind clinical trial of cannabis-based medicinal product (Sativex) in painful diabetic neuropathy: depression is a major confounding factor |
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|journal=Diabetes Care |
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|volume=161 |
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|pages=33 |
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|year=2009 |
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|month=October |
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|issue=1 |
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|pmid=19808912 |
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|url= |
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}}</ref> β-Sitosterol should be avoided during pregnancy and breast-feeding, since not enough is known about its effects on unborn and newborn children. β-Sitosterol is also not recommended for individuals with ], a rare inherited fat storage disease. Because people with this condition have too much β-sitosterol and related fats in their system, taking β-sitosterol will only worsen this condition. High levels of β-sitosterol concentrations in blood have been correlated with increased severity of heart disease in men having previously suffered from heart attacks.<ref name="Nutr">{{cite journal |author=Assmann G, Cullen P, Erbey J, Ramey DR, Kannenberg F, Schulte H |title=Plasma sitosterol elevations are associated with an increased incidence of coronary events in men: results of a nested case-control analysis of the Prospective Cardiovascular Münster (PROCAM) study |journal=Nutrition, Metabolism, and Cardiovascular Diseases : NMCD |volume=16 |issue=1 |pages=13–21 |year=2006 |month=January |pmid=16399487 |doi=10.1016/j.numecd.2005.04.001}}</ref> |
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== See also == |
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==See also== |
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* ], a β-sitosteryl glucoside found in the ] plant. |
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* ] |
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==References== |
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==References== |
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{{Reflist}} |
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<references/> |
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{{Phytosterols}} |
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{{Phytosterols}} |
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{{Androgen receptor modulators}} |
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{{Estrogen receptor modulators}} |
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{{DEFAULTSORT:Sitosterol, beta-}} |
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{{DEFAULTSORT:Sitosterol, β-}} |
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