Determination of tocopherols and sterols in vegetable oils by solid-phase extraction and subsequent capillary gas chromatographic analysis

Lechner, Marion; Reiter, Birgit; Lorbeer, Eberhard

doi:10.1016/s0021-9673(99)00751-7

Cited by 97 publications

(65 citation statements)

References 16 publications

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“…To isolate the non-glyceridic components (hydrocarbons, tocopherols, sterols and sterol esters) from the slightly more polar triacylglycerol matrix, solid phase extraction SPE (silicagel) has been used [75]. Prior to SPE, the free hydroxyl group of sterols and tocopherols were silylated to reduce their polarity.…”

Section: Solvent Extractionmentioning

confidence: 99%

Analysis of phytosterols in foods

Lagarda

García‐Llatas

Farré

2006

Journal of Pharmaceutical and Biomedical Analysis

277

208

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Phytosterols are bioactive compounds, one of their most studied and outstanding properties being their cholesterol-lowering activity. This explains the growing interest in the phytosterol contents of foods as either intrinsic or added components. The different steps (extraction, saponification, clean up, chromatographic determination) of plant sterol determination are reviewed, and emphasis is placed on the methods used to assay different phytosterols in food.

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Section: Solvent Extractionmentioning

confidence: 99%

Analysis of phytosterols in foods

Lagarda

García‐Llatas

Farré

2006

Journal of Pharmaceutical and Biomedical Analysis

277

208

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“…Samples were dried down under nitrogen and resuspended in 200 l of a 1:1 (v/v) mixture of pyridine, bis(trimethylsilyl)trifluoroacetamide, 1% trimethylchlorosilane for trimethylsilylation (TMS) of free hydroxyl groups (37,38). Each TMS treatment extract was diluted by addition of 0.5 ml of petroleum ether, hexane (1:1) and passed over a silica gel minicolumn that was pretreated with hexane, petroleum ether (1:1, v/v) (39). Sterols were eluted with hexane, ethyl acetate (1:1, v/v).…”

Section: Metabolic Radiolabeling and Analysis Of Sterols And Neutral mentioning

confidence: 99%

Characterizing Sterol Defect Suppressors Uncovers a Novel Transcriptional Signaling Pathway Regulating Zymosterol Biosynthesis

Germann

Gallo

Donahue

et al. 2005

Journal of Biological Chemistry

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erg26-1ts cells harbor defects in the 4␣-carboxysterol-C3 dehydrogenase activity necessary for conversion of 4,4-dimethylzymosterol to zymosterol. Mutant cells accumulate toxic 4-carboxysterols and are inviable at high temperature. A genetic screen aimed at cloning recessive mutations remediating the temperature sensitive growth defect has resulted in the isolation of four complementation groups, ets1-4 (erg26-1 ts temperature sensitive suppressor). We describe the characterization of ets1-1 and ets2-1. Gas chromatography/mass spectrometry analyses demonstrate that erg26-1 ts ets1-1 and erg26-1 ts ets2-1 cells do not accumulate 4-carboxysterols, rather these cells have increased levels of squalene and squalene epoxide, respectively. ets1-1 and ets2-1 cells accumulate these same sterol intermediates. Chromosomal integration of ERG1 and ERG7 at their loci in erg26-1 ts ets1-1 and erg26-1 ts ets2-1 mutants, respectively, results in the loss of accumulation of squalene and squalene epoxide, re-accumulation of 4-carboxysterols and cell inviability at high temperature. Enzymatic assays demonstrate that mutants harboring the ets1-1 allele have decreased squalene epoxidase activity, while those containing the ets2-1 allele show weakened oxidosqualene cyclase activity. Thus, ETS1 and ETS2 are allelic to ERG1 and ERG7, respectively. We have mapped mutations within the erg1-1/ ets1-1 (G247D) and erg7-1/ets2-1 (D530N, V615E) alleles that suppress the inviability of erg26-1 ts at high temperature, and cause accumulation of sterol intermediates and decreased enzymatic activities. Finally using erg1-1 and erg7-1 mutant strains, we demonstrate that the expression of the ERG25/26/27 genes required for zymosterol biosynthesis are coordinately transcriptionally regulated, along with ERG1 and ERG7, in response to blocks in sterol biosynthesis. Transcriptional regulation requires the transcription factors, Upc2p and Ecm22p.

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“…Samples were dried down under nitrogen and resuspended in 200 l of a 1:1 (v/v) mixture of pyridine/ bis(trimethylsilyl)trifluoroacetamide, 1% trimethylchlorosilane for trimethylsilylation (TMS) of free hydroxyl groups (42,43). Each TMS treatment extract was diluted by addition of 0.5 ml petroleum ether/ hexane (1:1) and passed over a silica gel mini-column that was pretreated with hexane/petroleum ether (1:1, v/v) (44). Sterols were eluted with hexane/ethyl acetate (1:1, v/v).…”

Section: Gc/ms Analysis Of Fattymentioning

confidence: 99%

Yeast Cells Lacking the ARV1 Gene Harbor Defects in Sphingolipid Metabolism

Swain¹,

Stukey²,

McDonough³

et al. 2002

Journal of Biological Chemistry

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]dihydrosphingosine radiolabeling studies demonstrated that mutant cells had reduced rates of biosynthesis and lower steadystate levels of complex sphingolipids while accumulating certain hydroxylated ceramide species. Phospholipid radiolabeling studies showed that arv1⌬ cells harbored defects in the rates of biosynthesis and steadystate levels of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylglycerol. Neutral lipid radiolabeling studies indicated that the rate of biosynthesis and steady-state levels of sterol ester were increased in arv1⌬ cells. Moreover, these same studies demonstrated that arv1⌬ cells had decreased rates of biosynthesis and steady-state levels of total fatty acid and fatty acid alcohols. Gas chromatography/mass spectrometry analyses examining different fatty acid species showed that arv1⌬ cells had decreased levels of C18:1 fatty acid. Additional gas chromatography/mass spectrometry analyses determining the levels of various molecular sterol species in arv1⌬ cells showed that mutant cells accumulated early sterol intermediates. Using fluorescence microscopy we found that GFP-Arv1p localizes to the endoplasmic reticulum and Golgi. Interestingly, the heterologous expression of the human ARV1 cDNA suppressed the sphingolipid metabolic defects of arv1⌬ cells. We hypothesize that in eukaryotic cells, Arv1p functions in the sphingolipid metabolic pathway perhaps as a transporter of ceramides between the endoplasmic reticulum and Golgi.Sphingolipids serve as constituents of membrane bilayers (1) and have emerged as potent signaling metabolites (2-5). Sphingolipid synthesis in eukaryotes begins with the condensation of serine and palmitoyl-CoA, a reaction catalyzed by the Lcb1p/ Lcb2p serine palmitoyltransferase subunits (Fig. 1) (6 -10). Ceramide serves as the backbone for all complex sphingolipids, and its biosynthesis is the point where animal and fungal sphingolipid biosynthesis begin to diverge (11). In higher eukaryotes, there are over three hundred different types of complex sphingolipids found in membranes (1), whereas in the yeast S. cerevisiae there are three, inositolphosphorylceramide (IPC), 1 mannose inositolphosphorylceramide (MIPC), and mannose diinositolphosphorylceramide (MIP 2 C). However, IPC, MIPC, and MIP 2 C lipids can differ in their hydroxylation state, giving rise to fifteen possible complex sphingolipids (11).The accumulation of free cholesterol in animal cells causes toxicity (12). One mechanism by which cells relieve this toxic effect is through the use of the membrane-associated SREBP transcription factors, which precisely regulate the genes that are required for sterol biosynthesis and LDL receptor expression (13,14). Worgall et al. (15) recently showed that SREBP activation was regulated by ceramide. Others have shown that animal cells regulate sphingolipid metabolism in response to subtle and transient changes in cholesterol (16,17). In S. cerevisiae, sphingolipid metabolism appears to be coordinately regulated with phospholipid an...

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Determination of tocopherols and sterols in vegetable oils by solid-phase extraction and subsequent capillary gas chromatographic analysis

Cited by 97 publications

References 16 publications

Analysis of phytosterols in foods

Analysis of phytosterols in foods

Characterizing Sterol Defect Suppressors Uncovers a Novel Transcriptional Signaling Pathway Regulating Zymosterol Biosynthesis

Yeast Cells Lacking the ARV1 Gene Harbor Defects in Sphingolipid Metabolism

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