- Cholesterol degradation in archaeological pottery mediated by fired clay and fatty acid pro-oxidants
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Cholesterol is generally absent in animal fat residues preserved in archaeological ceramic vessels. It is known from edible oil refining that during bleaching with activated clay sterols are degraded, largely via oxidation. Laboratory heating experiments
- Hammann, Simon,Cramp, Lucy J.E.,Whittle, Mathilda,Evershed, Richard P.
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supporting information
p. 4401 - 4404
(2018/11/23)
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- Metal-Free Allylic Oxidation of Steroids Using TBAI/TBHP Organocatalytic Protocol
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A mild, efficient and organocatalytic allylic oxidation of steroids using a TBAI/TBHP protocol has been developed. A range of bioactive Δ5-en-7-ones can be easily prepared from the corresponding Δ5-steroids. The methodology features several advantages, including readily available starting materials, environmentally benign oxidant, high functional group compatibility, and metal-free catalysis.
- Lam, Ying-Pong,Yeung, Ying-Yeung
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supporting information
p. 2369 - 2372
(2018/04/19)
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- Effect of Eleven Antioxidants in Inhibiting Thermal Oxidation of Cholesterol
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Eleven antioxidants including nine phenolic compounds (rutin, quercetin, hesperidin, hesperetin, naringin, naringenin, chlorogenic acid, caffeic acid, ferulic acid), vitamin E (α-tocopherol), and butylated hydroxytoluene (BHT) were selected to investigate their inhibitory effects on thermal oxidation of cholesterol in air and lard. The results indicated that the unoxidized cholesterol decreased with heating time whilst cholesterol oxidation products (COPs) increased with heating time. The major COPs produced were 7α-hydroxycholesterol, 7β-hydroxycholesterol, 5,6β-epoxycholesterol, 5,6α-epoxycholesterol, and 7-ketocholesterol. When cholesterol was heated in air for an hour, rutin, quercetin, chlorogenic acid, and caffeic acid showed a strong inhibitory effect. When cholesterol was heated in lard, caffeic acid, quercetin, and chlorogenic acid demonstrated inhibitory action during the initial 0.5 h (p a high flame is recommended. If baking or deep fat frying food in oil, it is best to limit cooking time to within 0.5 h.
- Xu, Guihua,Liu, Donghong,Zhao, Gongling,Chen, Shiguo,Wang, Jun,Ye, Xingqian
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p. 215 - 225
(2016/02/03)
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- Cholesterol transformations during heat treatment
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The aim of the study was to characterise products of cholesterol standard changes during thermal processing. Cholesterol was heated at 120 °C, 150 °C, 180 °C and 220 °C from 30 to 180 min. The highest losses of cholesterol content were found during thermal processing at 220 °C, whereas the highest content of cholesterol oxidation products was observed at temperature of 150 °C. The production of volatile compounds was stimulated by the increase of temperature. Treatment of cholesterol at higher temperatures i.e. 180 °C and 220 °C led to the formation of polymers and other products e.g. cholestadienes and fragmented cholesterol molecules. Further studies are required to identify the structure of cholesterol oligomers and to establish volatile compounds, which are markers of cholesterol transformations, mainly oxidation.
- Derewiaka,Molińska
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p. 233 - 240
(2015/01/09)
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- Cholesterol hydroperoxides generate singlet molecular oxygen [O 2(1Δg)]: Near-IR emission, 18O-labeled hydroperoxides, and mass spectrometry
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In mammalian membranes, cholesterol is concentrated in lipid rafts. The generation of cholesterol hydroperoxides (ChOOHs) and their decomposition products induces various types of cell damage. The decomposition of some organic hydroperoxides into peroxyl
- Uemi, Miriam,Ronsein, Graziella E.,Prado, Fernanda M.,Motta, Flavia D.,Miyamoto, Sayuri,Medeiros, Marisa H. G.,Di Mascio, Paolo
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experimental part
p. 887 - 895
(2012/04/11)
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- Synthesis of 7-hydroperoxycholesterol and its separation, identification, and quantification in cholesterol heated model systems
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7-Hydroperoxycholesterol is considered to be an intermediate compound of the cholesterol oxidation path as the first product formed when cholesterol is oxidized by triplet oxygen. However, there is a limitation on cholesterol mechanism studies because of the lack of 7-hydroperoxycholesterol analytical standard due to its low stability. To verify the formation of hydroperoxides in cholesterol model systems heated at 140, 180, and 220 °C, 7α-hydroperoxycholesterol was synthesized by cholesterol photooxidation followed by rearrangement at room temperature in chloroform. Its structure was confirmed on the basis of 13C NMR and mass spectra obtained by APCI-LC-MS. The synthesized compound was also used as standard for the quantification of 7-hydroperoxycholesterol as the sum of 7α-and 7β-hydroperoxycholesterol. The results demonstrated that 7-hydroperoxycholesterol is the first compound formed when the temperature is lower (140 °C). However, the concentration of the 7-hydroperoxycholesterol depends on the temperature and time of exposure: the higher the time, the higher the amount of 7-hydroperoxycholesterol at lower temperatures, and the lower the time, the lower the amount of 7-hydroperoxycholesterol at higher temperatures (180 and 220 °C). By the formation of 7-hydroperoxycholesterol, the known cholesterol oxidation mechanism in three phases (initiation, propagation, and termination) could be confirmed; once at lower temperatures, the stage of cholesterol oxidation is at initiation, at which hydroperoxide formation predominates.
- Nogueira, Gislaine C.,Costa, Bruna Z.,Crotti, Antonio E. M.,Bragagnolo, Neura
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experimental part
p. 10226 - 10230
(2011/05/05)
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- Allylic oxidations catalyzed by dirhodium caprolactamate via aqueous tert-butyl hydroperoxide: The role of the tert-butylperoxy radical
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Dirhodium(II) caprolactamate exhibits optimal efficiency for the production of the tert-butylperoxy radical, which is a selective reagent for hydrogen atom abstraction. These oxidation reactions occur with aqueous tert-butyl hydroperoxide (TBHP) without rapid hydrolysis of the caprolactamate ligands on dirhodium. Allylic oxidations of enones yield the corresponding enedione in moderate to high yields, and applications include allylic oxidations of steroidal enones. Although methylene oxidation to a ketone is more effective, methyl oxidation to a carboxylic acid can also be achieved. The superior efficiency of dirhodium(II) caprolactamate as a catalyst for allylic oxidations by TBHP (mol % of catalyst, % conversion) is described in comparative studies with other metal catalysts that are also reported to be effective for allylic oxidations. That different catalysts produce essentially the same mixture of products with the same relative yields suggests that the catalyst is not involved in product-forming steps. Mechanistic implications arising from studies of allylic oxidation with enones provide new insights into factors that control product formation. A previously undisclosed disproportionation pathway, catalyzed by the tert-butoxy radical, of mixed peroxides for the formation of ketone products via allylic oxidation has been uncovered.
- McLaughlin, Emily C.,Choi, Hojae,Wang, Kan,Chiou, Grace,Doyle, Michael P.
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supporting information; experimental part
p. 730 - 738
(2009/07/04)
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- Allylic Oxidations Catalyzed by Dirhodium Catalysts under Aqueous Conditions
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The present invention relates to compositions and methods for achieving the efficient allylic oxidation of organic molecules, especially olefins and steroids, under aqueous conditions. The invention concerns the use of dirhodium (II,II) “paddlewheel complexes, and in particular, dirhodium carboximate and tert-butyl hydroperoxide as catalysts for the reaction. The use of aqueous conditions is particularly advantageous in the allylic oxidation of 7-keto steroids, which could not be effectively oxidized using anhydrous methods, and in extending allylic oxidation to enamides and enol ethers.
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Page/Page column 16-18; 20
(2009/04/24)
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- A comparison of the potential unfavorable effects of oxycholesterol and oxyphytosterol in mice: Different effects, on cerebral 24S-hydroxychoelsterol and serum triacylglycerols levels
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Sterol oxidation products derived from cholesterol and phytosterol are formed during the processing and storage of foods. The objective of the present study was to assess the potential unfavorable effects of oxysterols in mice. C57BL/6J mice were fed an AIN-93G-based diet containing 0.2 g/kg of oxycholesterol or oxyphytosterol for 4 weeks. The most abundant oxysterol in the diet was 7-ketosterol, but α-epoxycholesterol, β-epoxycholesterol, or 7α-hydroxyphytosterol, and 7β-hydroxyphytosterol were more prominent than 7-ketosterol in the serum and liver respectively. Consumption of both oxysterols resulted in an increased in 4β-hydroxycholesterol and total oxycholesterol in the liver, but the oxycholesterol-fed mice had a lower level of cerebral 24S-hydroxycholesterol and a higher level of the serum triacylglycerols than the control and oxyphytosterol groups. These results indicate that both oxysterols in the diet are accumulated in the body, but that the biological effect of oxycholesterol is different from that of oxyphytosterol.
- Bang, Hyun-Jung,Arakawa, Chiyo,Takada, Michihiro,Sato, Masao,Imaizumi, Katsumi
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experimental part
p. 3128 - 3133
(2009/05/09)
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- Process for oxidation of steroidal compounds having allylic groups
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The instant invention involves a process for oxidizing compounds containing an allylic group, i.e. those containing an allylic hydrogen or allylic alcohol group, to the corresponding enones, using a ruthenium-based catalyst in the presence of a hydroperoxide. Particularly, Δ-5-steroidal alkenes can be oxidized to the corresponding Δ-5-7-keto alkenes.
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- Cytotoxicity and suppression of immunoglobulin production against human Namalwa cells caused by oxidized cholesterol
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The effects of oxidized cholesterols on proliferation and IgM production of human lymphoblastoid Namalwa cells were examined. An oxidized cholesterol mixture, in contrast to cholesterol, was a potent cytotoxin to Namalwa cells. Among oxidized cholesterols examined, 25-hydroxycholesterol was the most cytotoxic. However, no oxidized cholesterol examined suppressed IgM production, although cholestanetriol and 7-ketocholesterol did suppress it. Thus, oxidized cholesterols are cytotoxic to lymphocytes, while the influence on the immunoglobulin production may be marginal.
- Osada, Kyoichi,Kodama, Takehiro,Matsuo, Noritaka,Yamada, Koji,Sugano, Michihiro
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p. 1362 - 1364
(2007/10/03)
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- Oxidation of Cholesterol by Heating
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Oxidation of pure cholesterol during heating in an air oven at high temperature was studied.Cholesterol was virtually stable during heating at 100 deg C for 24 h but was unstable at temperature above 120 deg C.In the heated choleaterol preparations, a number of oxidized derivatives were detected by a combination of thin-layer chromatography and capillary gas chromatography-mass spectrometry.Major oxidized sterols were 7α-hydroxycholesterol, 7β-hydroxycholesterol, 5α-epoxycholesterol, 5β-epoxycholesterol, cholestanetriol, and 7-ketocholesterol.Various oxidized cholesterol derivatives were produced during heating above 120 deg C within a relatively short time (1h).The composition of the oxidized products differed depending on temperature and time of heating.When cholesterol was heated at 150 deg C, the production of oxidized cholesterol was maximum, and 7-ketocholesterol was the most predominant oxidized product.Heating at 120 deg C also produced oxidized cholesterol to some extent, whereas only marginal amounts of oxidized cholesterols were produced at 100 deg C and at 200 deg C cholesterol was almost decomposed in a short time.
- Osada, Kyoichi,Kodama, Takehiro,Yamada, Koji,Sugano, Michihiro
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p. 1198 - 1202
(2007/10/02)
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- Catalytic Oxygenation of Cholesterol with a Platinum Catalyst under Moderate Pressure of Oxygen
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The catalytic oxigenation of cholesterol 1 with a platinum black catalyst under moderate pressure (20-25 atm) of oxygen yielded eleven oxidation products, 3-13a.The reaction pathway of the catalytic oxygenation is discussed on the basis of the results for several reaction conditions.
- Sakamaki, Hiroshi,Take, Masa-aki,Akihisa, Toshihiro,Matsumoto, Taro,Ichinohe, Yoshiyuki
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p. 3023 - 3025
(2007/10/02)
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- Iron-catalyzed Autoxidation of Liposomal Cholesterol
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The autooxidation of cholesterol in a benzene solution of egg lecithin and Fe(acac)3, giving products variously oxygenated in the steroidal ring B, proceeded with consumption of the unsaturated long chain fatty acid moieties, particularly C18:2, in the lechitin molecule.The reaction showed a marked β-stereoselectivity of epoxidation and was inhibited by a radical scavenger (BHT).Cholesterol was highly susceptible to ferric iron-catalyzed autoxidation within liposomes prepared by using lechitin.The oxidative degradation of the unsaturated moieties, C18:1 and C18:2, in the lechitin led to allylic oxidation as well as the β-stereoselective epoxidation of cholesterol.A radical scavenger inhibited both the degradation of these moities and the oxygenation of cholesterol.The oxygenation was retarded in liposomes prepared by using saturated dipalmitoyl lecithin, and was dominated by allylic oxidation giving cholesteryl hydroperoxide as the main product.Cholesterol in the liposomes containing egg lecithin was, thus, assumed to be co-oxidized with the unsaturated fatty acid moieties by radical pathway, when the liposomes were autoxidized in the presence of ferric catalyst.Keywords - cholesterol; egg lecithin; liposome; liposomal cholesterol; autoxidation; stereoselective epoxidation; lipid peroxidation; co-oxidation; radical pathway; iron catalyst
- Muto, Toshiki,Tanaka, Jun,Miura, Toshiaki,Kimura, Michiya
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p. 1561 - 1566
(2007/10/02)
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- Iron-catalyzed Autoxidation of Cholesterol in the Presence of Unsaturated Long-Chain Fatty Acid
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Oxy-functionalization of cholesteryl acetate (1a) occured, giving 3β-acetoxy-5,6-epoxycholestane (2a), 3β-acetoxycholest-5-en-7-one (3a), 3β-acetoxycholest-5-en-7-ol (4a), and an unidentified product (5), when 1a was oxidized by a system consisting of Fe(acac)3, and the hydroperoxide of an unsaturated long-chain fatty aicd (LH) such as oleic, linolic or linolenic acid (Table I).The epoxidation of stilbene by the same system was found to be non-stereospecific.These results and the fact that the reaction in this system was inhibited by a radical scavanger (BHT) were fairly compatible with those obtained with the Fe(acac)3-tBuOOH system, which is assumed to generate oxy and peroxy radicals.Autoxidation of 1a and cholesterol (1b) in the presence of Fe(acac)3 and LH proceeded after a time-lag of several hours and was also inhibited be BHT.The marked stereoselectivity of β-epoxidation (β/α+β=0.72) and the extent (about 30-40percent) of allylic oxidation in the autoxidation were in fair agreement with those found for 1a in the Fe(acac)3-LOOH system (Table II).Autoxidation of stilbene in the presence of Fe(acac)3 and LH also led to non-stereospecific epoxidation.Thus, the autoxidation of cholesterols (1a and 1b) in the Fe(acac)3-LH system was assumed to be a radical reaction in which LOO. and LO. are the attacking species.Keywords - autoxidation; cholesterol; co-oxidation; epoxidation; hydroperoxide; lipid peroxidation; radical pathway; stilbene; tris(acetylaceto)iron(III); unsaturated long-chain fatty acid
- Muto, Toshiki,Tanaka, Jun,Miura, Toshiaki,Kimura, Michiya
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p. 3172 - 3177
(2007/10/02)
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