Mass Spectrometry Characterization of the 5α-, 7α-, and 7β-Hydroxy Derivatives of β-Sitosterol, Campesterol, Stigmasterol, and Brassicasterol

Bortolomeazzi, Renzo; Zan, M De; Pizzale, Lorena; Purcaro, Giorgia

doi:10.1021/jf9812580

Cited by 57 publications

(39 citation statements)

References 30 publications

(28 reference statements)

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“…Six bands were identified as follows: nonoxidized phytosterols (band 1, R f ) 0.58), epoxy derivatives (band 2, R f ) 0.38), 7-keto (band 3, R f ) 0.32), 7 -hydroxy (band 4, R f ) 0.25), 7R-hydroxy (band 5, R f ) 0.2), and triol derivatives (band 6, R f ) 0.06). The bands corresponding to 7R-hydroxy and 7 -hydroxy derivatives (bands 5 and 4, respectively) displayed a blue color after treatment with sulfuric acid, which is in agreement with Chicloye et al (30), Daly et al (31), and Bortolomeazzi et al (32). Injection of these bands in the GC-MS showed that 7-ketosterols coeluted in the TLC plate with other compounds, which had a smaller GC peak area and lower GC retention time with respect to those of their corresponding 7-keto derivatives (see Figure 1).…”

Section: Resultssupporting

confidence: 90%

Levels of Phytosterol Oxides in Enriched and Nonenriched Spreads: Application of a Thin-Layer Chromatography−Gas Chromatography Methodology

Conchillo

Cercaci

Ansorena

et al. 2005

J. Agric. Food Chem.

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The content of phytosterol oxidation products (POPs) in enriched and nonenriched commercial spreads was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Oxides of -sitosterol, campesterol, and stigmasterol were produced by thermo-oxidation (7-hydroxy, 7-keto, and epoxy derivatives) and chemical synthesis (triol derivatives), which were then separated and identified by TLC-GC. Their identification was further confirmed by GC-mass spectrometry (GC-MS). The total amounts of phytosterols found were 6.07 and 0.33 g/100 g of sample in phytosterol-enriched and nonenriched spread, respectively, whereas the total POPs contents were 45.60 and 13.31 mg/kg of sample in the enriched and nonenriched products. The main POPs found were the 7-keto derivatives of all phytosterols analyzed; 7-ketositosterol was the most abundant one (14.96 and 5.93 mg/kg of sample in phytosterol-enriched and nonenriched spread). No -epoxy and triol derivatives were detected in both types of samples. The enriched spread presented a lower phytosterol oxidation rate (0.07%) than the nonenriched one (0.41%).

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Section: Resultssupporting

confidence: 90%

Levels of Phytosterol Oxides in Enriched and Nonenriched Spreads: Application of a Thin-Layer Chromatography−Gas Chromatography Methodology

Conchillo

Cercaci

Ansorena

et al. 2005

J. Agric. Food Chem.

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“…However, the presence of unsaturated bonds in the structure results in their being oxidized under the influence of external factors such as temperature, light, enzymes or oxidation products of other compounds. As a result of autoxidation or photo-oxidation of phytosterols, derivatives of hydroxy-, keto-, epoxysterols as well as triols of these compounds are formed, which may have a negative effect on the human organism [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Stabilization of phytosterols in rapeseed oil by natural antioxidants during heating

Kmiecik

Korczak

Rudzińska

et al. 2009

Euro J Lipid Sci & Tech

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Antioxidants are substances that can reduce negative changes in fat. Many antioxidants are very effective during storage, but during heating they lose their properties. It is very important to find antioxidants that will be stable at high temperatures and protect fat throughout the entire frying process. The aim of this study was to estimate the effect of natural and synthetic antioxidants on changes in phytosterols of rapeseed oil during heating. Oil with antioxidants was heated at 180 7C for 4 h in a Rancimat ® and in an Oxidograph ® . Ethanol extract of rosemary, ethanol extract of green tea, and BHT were used in the study. The contents of phytosterols (sitosterol, campesterol, avenasterol, brassicasterol, stigmasterol) and oxyphytosterols (7a-and 7b-hydroxysterol, 5a,6a-and 5b,6b-epoxysterol, 7-ketosterol and triols) were estimated by gas chromatography. In all samples with antioxidants, a lower decrease of phytosterols and a lower increase of total oxyphytosterols were observed in comparison with the control sample (without antioxidant). The antioxidant effect depends on the type of the antioxidant and the heating conditions. The best results were observed in samples with natural antioxidants. BHT was a substance that protected phytosterols as well, but not as effectively as the other antioxidants.

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“…Hydroxylation of toxic oxysterols like 7kCh may be necessary in the oxidative environment of the photoreceptors. There is significant in vitro evidence demonstrating photo-oxidation of cholesterol (Bortolomeazzi et al, 1999), although the presence of 7kCh and other oxysterols in the retina has not been demonstrated. Alternatively, CYP27A1 may be generating 27OHCh and/or other oxysterols for the purpose of activating X-receptors (Escher et al, 2003;Berkenstam and Gustafsson, 2005) and/or other molecules that could alter gene expression.…”

Section: Introductionmentioning

confidence: 99%

“…The highly oxidative retinal environment coupled with light exposure (photo-oxidation) provides excellent opportunities for lipid oxidation (Girotti, 1992; Girotti and Kriska, 2004, reviews). While the formation of oxidized sterols in the retina has not been studied in detail, oxidation and photo-oxidation products of cholesterol on other tissues and in vitro indicates that it readily forms 7α-and 7β-hydroxy derivatives (Bortolomeazzi et al, 1999), which are known precursors of 7-ketocholesterol (Dzeletovic et al, 1995).The monkey retina was chosen for this study for several reasons. We can obtain fresh ocular tissue from young animals.…”

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Expression and localization of sterol 27-hydroxylase (CYP27A1) in monkey retina

Lee

Fuda

Javitt

et al. 2006

Experimental Eye Research

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Sterol 27-hydroxylase (CYP27A1) is a mitochondrial P-450 enzyme with broad substrate specificity for C27 sterols including 7-ketocholesterol (7kCh). CYP27A1 is widely expressed in human tissues but has not been previously demonstrated in the retina. In this study, we examined the expression and localization of CYP27A1 in the monkey retina where it localized mainly to the photoreceptor inner segments. CYP27A1 was also observed in Müller cells with faint immuno staining detected in the RPE and choriocapillaris. We also determined that the 27-hydroxylation of 7-ketocholesterol (27OH7kCh) rendered it non-toxic to cultured RPE cells. Moreover, the 27OH7kCh when mixed with 7-ketocholesterol significantly reduced the toxicity of 7-ketocholesterol. These data, when taken in context of the known functions of CYP27A1 imply that expression in the retina serves to modify the biological activity of oxidized sterols that are either transported or generated locally by photooxidation. Published by Elsevier Ltd. Keywords cholesterol efflux; macula; 7-ketocholesterol; ARPE19; photoreceptors The sterol 27-hydroxylase (CYP27A1:P450c27, Andersson et al., 1989) is a mitochondrial enzyme that performs multiple functions (Javitt, 2002, review): it is known to catalyze bile acid hydroxylations (Russell, 2003, review) and to activate vitamin D (Usui et al., 1990); furthermore, the formation of 27-hydroxycholesterol (27OHCh) by CYP27A1 has been demonstrated to stimulate cholesterol efflux in cultured cells (Escher et al., 2003). CYP27A1 is deficient in individual with the rare disease cerebrotendinous xanthomatosis (CTX) . CTX patients suffer from progressive neurological impairment as well as accelerated atherosclerosis and cataracts (Moghadasian, 2004, review).CYP27A1 readily hydroxylates the oxysterol 7-ketocholesterol (7kCh) to 27-hydroxy-7-ketocholesterol (27OH7kCh) (Brown et al., 2000), which is highly toxic to a variety of cells (Lyons and Brown, 1999) including RPE cells and is the main cholesterol oxide in oxidized low density lipoprotein (Brown et al., 1996) (Brown and Jessup, 1999).The rationale for this study is threefold: (1) CYP27A1 is known to be involved in the cholesterol efflux pathway (Escher et al., 2003), (2) CYP27A1 is known to be involved in the metabolism of 7kCh (Brown et al., 2000;Lyons and Brown, 2001;Jessup and Brown, 2005) and (3) despite the extensive knowledge of cholesterol hydroxylation in the brain (Björkem and Meaney, 2004; Diestschy and Turley, 2004, reviews), there are no published reports concerning CYP27A1 (or other sterol hydroxylases) in the retina. The retina is known to perform de novo synthesis (Fliesler et al., 1993) as well as cholesterol uptake from circulating blood lipoproteins (Elner, 2002;Gordiyenko et al., 2004). However, little is known about the cholesterol efflux or how the retina maintains cholesterol homeostasis. CYP27A1 may be involved in cholesterol efflux by forming 27OHCh which can change the lipid composition of the plasma membrane and/or can alter gene expression by ...

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Mass Spectrometry Characterization of the 5α-, 7α-, and 7β-Hydroxy Derivatives of β-Sitosterol, Campesterol, Stigmasterol, and Brassicasterol

Cited by 57 publications

References 30 publications

Levels of Phytosterol Oxides in Enriched and Nonenriched Spreads: Application of a Thin-Layer Chromatography−Gas Chromatography Methodology

Levels of Phytosterol Oxides in Enriched and Nonenriched Spreads: Application of a Thin-Layer Chromatography−Gas Chromatography Methodology

Stabilization of phytosterols in rapeseed oil by natural antioxidants during heating

Expression and localization of sterol 27-hydroxylase (CYP27A1) in monkey retina

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