bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interference of 7‐dehydrocholesterol in α‐tocopherol determination by high‐performance liquid chromatography: A possible screening test for the smith‐lemli‐opitz syndrome
Authors: Michel F. , Cristol J. P. , Vernet M. H. , Feillet C. , Carbonneau M. ‐A. , Léger C. L. , Castel J. , Descomps B. 
Published: May 2007

Abstract7‐Dehydrocholesterol (7‐DHC), a normal cholesterol precursor, accumulates in plasma and tissues of patients affected by the Smith‐Lemli‐Opitz (SLO) syndrome, a recessive autosomic disease characterized by mental retardation and physical malformations. In these patients, we suspected that 7‐DHC interfered with α‐tocopherol (α‐T) determination because this steroid could be coeluted with α‐tocopherol acetate (α‐TA), an internal standard commonly used for α‐T determination, and because the conjugated dienic structure of 7‐DHC strongly absorbs at 292 nm. The aim of this work was (i) to characterize the interfering material and (ii) to evaluate the possibility of a rapid screening test for SLO syndrome identification from 7‐DHC determination by reverse‐phase chromatography high‐performance liquid chromatography (HPLC). Human plasmas (control and SLO syndrome) were extracted with hexane after ethanol protein precipitation and addition of ascorbic acid as protective agent plus α‐TA or δ‐tocopherol (δ‐T) as internal standards. The dry hexane extract was used for HPLC, and trimethylsilyl ethers derivatives of the extracts were submitted to gas chromatography (GC) and gas chromatography‐mass spectrometry (GC‐MS). The material interfering in the α‐T determination was unambiguously identified to 7‐DHC by retention time (RT) relative to standard, RT relative to δ‐T, and analysis of the eluted material by GC and by GC‐MS. In α‐T determination, the interference can be eliminated by using δ‐T as internal standard instead of α‐TA. Rapid detection and evaluation of 7‐DHC in plasma appear to be possible by HPLC under the conditions described; comparison with the GC reference method suggests that the rapid HPLC determination of 7‐DHC in plasma can be used within the 1–40 mg/dL range, values commonly found in SLO syndrome.
Identification of conjugated fatty acids by gas chromatography‐mass spectrometry of 4‐methyl‐1,2,4‐triazoline‐3,5‐dione adducts
Authors: Dobson Gary 
Published: May 2007

Abstract4‐Methyl‐1,2,4‐triazoline‐3,5‐dione was reacted with conjugated fatty acid methyl esters to form Diels‐Alder cycloaddition products. The electron impact mass spectra of conjugated octadecadienoates and 9,11,13‐octadecatrienoate were simple and informative and allowed the positions of the double bonds to be determined. The dienes gave single adducts whereas the triene formed four products that corresponded to two stereoisomers of the adducts of the 9,11‐diene system and two of the 11,13‐diene system. The method can be used to complement other methods for identifying conjugated fatty acids.
Oxidation in fish lipids during thermal stress as studied by 13C nuclear magnetic resonance spectroscopy
Authors: Medina Isabel , Sacchi Raffaele , Giudicianni Italo , Aubourg Santiago 
Published: May 2007

Abstract13C Nuclear magnetic resonance spectroscopy has been applied to elucidate the mechanism of lipid oxidation occurring during thermal treatment of fish. Effects of temperature and time of processing have been studied by means of a model system of lipids, extracted from salmon (Salmo salar) muscle, to simulate industrial conditions of canning. Unsaturated fatty acids located at the sn‐2 position of the glycerol moiety were the most prone to oxidative damage. Regarding the mechanism of the reaction, results inferred from olefinic and methylenic resonances indicated a higher susceptibility of the allylic sites closest to the carbonyl group, followed by those placed near the methyl terminal group. Unsaturations located in the middle of the carbon chain did not show much damage. The glyceryl region provided an unusual resonance at 53.4 ppm, which could be assigned to a hydroxylic compound formed during process.
The presence of oxidizing enzyme activities in virgin olive oil
Authors: Georgalaki M. D. , Sotiroudis T. G. , Xenakis A. 
Published: May 2007

AbstractSamples of Greek virgin olive oils were examined for the presence of proteins and oxidative enzyme activities. All oil samples tested contained detectable amounts of protein, as well as lipoxygenase and polyphenol oxidase activities. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and size‐exclusion chromatography of olive oil extracts revealed the presence of low‐molecular‐mass (10–40 kDa) silver‐staining and ultraviolet‐absorbing components, respectively. Both lipoxygenase and polyphenol oxidase catalytic activities were heat‐ and protease‐sensitive, and they expressed Michaelis‐Menten kinetics.
Effect of oil replenishment during deep‐fat frying of frozen foods in sunflower oil and high‐oleic acid sunflower oil
Authors: Romero Antonio , Cuesta Carmen , Sánchez‐Muniz Francisco J. 
Published: May 2007

AbstractFrying stability of sunflower oil (SO) with 23% oleic acid and 61% linoleic acid, and of high‐oleic acid sunflower oil (HOSO) with 74% oleic acid and 13% linoleic acid was studied during 20 discontinuous deep‐fat fryings of various frozen foods, with or without frequent replenishment of the used oil with fresh oil. Alterations of both oils were measured by column, gas‐liquid and high‐performance size‐exclusion chromatography. Total polar content and compounds, related to thermoxidative changes, and diacylglycerides, related to hydrolytic changes, increased in all oils during frying but reached higher levels in SO than in HOSO. Nevertheless, the increased levels of diacylglycerides observed may result from the frozen potatoes prefried in palm oil. Oleic acid in HOSO and linoleic acid in SO significantly decreased, but the fatty acid modifications that occurred during the repeated fryings were not only related to thermoxidative alteration but also to interactions between the bath oil and the fat in the fried products. Data from this study also indicated that HOSO performed more satisfactorily than SO in repeated fryings of frozen foods. Moreover, frequent addition of fresh oil throughout the deep‐frying process minimized thermoxidative and hydrolytic changes in the frying oils and extended the frying life of the oils.
Antioxidant properties of myricetin and quercetin in oil and emulsions
Authors: Roedig‐Penman Andrea , Gordon Michael H. 
Published: May 2007

AbstractThe effect of quercetin and myricetin on the stability of sunflower oil and oil‐in‐water emulsions was studied by storage experiments monitored by measurement of peroxide values, conjugated dienes, and headspace volatile analysis. Myricetin showed strong antioxidant activity in oils stored at 60 or 30°C and in oil‐in‐water emulsions stored at 30°C, whether tocopherols or citric acid were present or not; however, quercetin showed similar antioxidant activity in stripped sunflower oil but no activity in oils that contained tocopherols and citric acid. This showed that myricetin is effective owing to strong radical scavenging and metal‐chelating properties, whereas quercetin has weaker radical scavenging activity, although it is also active by metal‐chelation. The effects of copper and iron salts on the antioxidant activity of myricetin and quercetin were studied in sunflower oil and oil‐in‐water emulsions. Quercetin and myricetin enhanced the prooxidant effect of cupric chloride in oil‐in‐water emulsions (pH 7.4), but this effect was not observed with cupric stearate. The addition of myricetin to emulsions that contained ferric chloride at pH 5.4 also produced a strong prooxidant effect, and small prooxidant effects of flavonols were also detected in the presence of cupric chloride under these conditions. However, myricetin and quercetin reduced the prooxidant effect of ferric palmitate in oils. Myricetin also showed a strong antioxidant effect in oil that contained cupric stearate, although quercetin had no significant effect on the oxidative stability of this system. It therefore appears that flavonols may exert a prooxidant effect in the presence of metal salts, but the nature of the metal salt is important in determining whether a prooxidant effect occurs.
Antioxidants from a heated histidine‐glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high‐performance liquid chromatography
Authors: Bersuder P. , Hole M. , Smith G. 
Published: May 2007

AbstractThe radical‐combining activity of Maillard reaction products [MRP(aq)], produced by heating d‐glucose and l‐histidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH·) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH· method showed a potential antioxidant activity of MRP(aq), which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP(aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH· method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze‐dried MRP(aq) was examined, and ethanol extracts showed the greatest activity by the DPPH· method. Consequently, the ethanol extract of freeze‐dried MRP(aq) was separated by means of preparative reverse‐phase high‐performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH· method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze‐dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n‐propyl gallate.
Use of α‐tocopherol acetate to improve fresh pig meat quality of full‐fat rapeseed‐fed pigs
Authors: Onibi G. E. , Scaife J. R. , Murray I. , Fowler V. R. 
Published: May 2007

AbstractThirty‐two pigs were allocated to one of four diets, FFRD0 and FFRD200, containing full‐fat rapeseed (FFR), 150 g/kg [25–50 kg liveweight (LW)], and 250 g/kg (50–90 kg LW), or CD0 and CD200, containing equivalent quantities of rapeseed meal and 34 g/kg (25–50 kg LW) or 59.2 g/kg (50–90 kg LW) coconut oil and lard (0.5:0.5, w/w). Diets FFRD200 and CD200 were supplemented with 200 mg/kg α‐tocopherol acetate (ATA). ATA supplementation significantly (P<0.001) reduced muscle drip loss. The melting point (°C) of subcutaneous fat was significantly lowered by FFR (P<0.001) but increased by ATA supplementation (P<0.05). Tissue α‐tocopherol (AT) concentrations were significantly increased by ATA supplementation. Longissimus dorsi AT concentration was positively correlated with AT concentration in subcutaneous fat (r=0.86) and in plasma at 35 (r=0.65) and 77 (r=0.85) days of feeding (P<0.001). In both L. dorsi and subcutaneous adipose tissue lipids, FFRD caused a significant (P<0.001) decrease in the ratio of n‐6 to n‐3 fatty acids and a significant (P<0.001) increase in the ratio of polyunsaturated to saturated fatty acids. AT supplementation significantly reduced the susceptibility of L. dorsi and subcutaneous fat to lipid oxidation during storage at 4°C for up to 16 d. For all dietary treatments and storage times, lipid oxidation [mg malondialdehyde (MDA)/kg muscle] was greater in the surface layer (0–2.5 mm) of L. dorsi than below the surface (2.5–5 mm). Oxidative stability of L. dorsi lipids to iron‐induced lipid peroxidation was significantly improved (P<0.001) by AT supplementation. Meat from pigs fed FFRD diets was significantly less stable to iron‐induced oxidation (nmoles MDA/mg protein) at the longer incubation periods (100 and 200 min). The susceptibility of L. dorsi to iron‐induced lipid oxidation decreased as the ratio of the tissue concentration of AT to unsaturated fatty acid increased.
Free radicals, oxidative stress, and antioxidants in human health and disease
Authors: Aruoma Okezie I. 
Published: May 2007

AbstractFree radicals and other reactive oxygen species (ROS) are constantly formed in the human body. Free‐radical mechanisms have been implicated in the pathology of several human diseases, including cancer, atherosclerosis, malaria, and rheumatoid arthritis and neurodegenerative diseases. For example, the superoxide radical (O2·−) and hydrogen peroxide (H2O2) are known to be generated in the brain and nervous systemin vivo, and several areas of the human brain are rich in iron, which appears to be easily mobilizable in a form that can stimulate free‐radical reactions. Antioxidant defenses to remove O2·−and H2O2exist. Superoxide dismutases (SOD) remove O2·−by greatly accelerating its conversion to H2O2. Catalases in peroxisomes convert H2O2into water and O2and help to dispose of H2O2generated by the action of the oxidase enzymes that are located in these organelles. Other important H2O2‐removing enzymes in human cells are the glutathione peroxidases. When produced in excess, ROS can cause tissue injury. However, tissue injury can itself cause ROS generation (e.g., by causing activation of phagocytes or releasing transition metal ions from damaged cells), which may (or may not, depending on the situation) contribute to a worsening of the injury. Assessment of oxidative damage to biomolecules by means of emerging technologies based on products of oxidative damage to DNA (e.g., 8‐hydroxydeoxyguanosine), lipids (e.g., isoprostanes), and proteins (altered amino acids) would not only advance our understanding of the underlying mechanisms but also facilitate supplementation and intervention studies designed and conducted to test antioxidant efficacy in human health and disease.
The tocopherol pattern in human serum is markedly influenced by intake of vitamin E drugs—Results of the german national health surveys
Authors: Melchert H. ‐U. , Pabel E. 
Published: May 2007

AbstractDuring national and regional health surveys, done from 1984–1995 in Germany, consumption data for all drugs used by the participants—approximately 18,000 persons—in the last 7 d before the examination were monitored with a detailed drug‐usage questionnaire. The groups examined are representative for the national and regional German inhabitant population aged 25–69 yr. In serum samples of subsamples of the study participants, all tocopherols were measured by isocratic high‐performance liquid chromatography (Si 60 column, fluorescence detection). Consumption data for tocopherol‐containing drugs showed that up to 5% of females and up to 3% of males of the study population used those drugs. During the study period, the serum content of α‐tocopherol (mean values ± SD) rose from 7.5 ± 2.6 mg/L serum to 11.8 ± 2.8 mg/L serum for nonusers and from 11.9 ± 4.3 mg/L serum to 15.3 ± 4.9 mg/L serum in tocopherol‐drug users. Throughout all studies, it could be shown that β‐ and γ‐tocopherol were heavily reduced in those persons taking daily doses ≥50 mg α‐tocopherol. The reduction of the two tocopherols is dose‐dependent and especially pronounced in females using high‐dose α‐tocopherol drugs. Owing to the emerging evidence of the physiological importance concerning the balance of the different tocopherols in biological systems, the possible benefits of using natural tocopherol mixtures from plant origin instead of pure RRR‐α‐tocopherol, gained from permethylation procedures, as vitamin supplements in human nutrition should be considered.
Improvement in the antioxidant status of plasma and low‐density lipoprotein in subjects receiving a red wine phenolics mixture
Authors: Carbonneau Marie‐Annette , Léger Claude L. , Descomps Bernard , Michel Françoise , Monnier Louis 
Published: May 2007

AbstractIt is commonly accepted that oxidized low‐density lipoprotein (ox‐LDL) plays an important role in coronary heart disease (CHD) and etiologically related atherogenesis. Consumption of wine may contribute to the low risk of CHD in the Mediterranean population. These findings raise the question of the in vivo antioxidant role of wine phenolic compounds after a prolonged supplementation period in healthy human volunteers. We found that subjects, receiving 2 g/d of an alcohol‐free red wine‐extracted phenolic compound (RWPC) mixture for 14 d (which was equivalent to about 1 L/d of the red wine), exhibited an increase in the plasma antioxidative capacity and in LDL vitamin E by blood sampling under fasting conditions. The fact that the LDL Cu2+‐oxidizability was not decreased can be explained by both the lack of phenolic compound affinity for the lipoprotein particle, highlighted by LDL dialysis, and the insufficient increase in LDL vitamin E, as shown by the relationship between vitamin E content and oxidation resistance of LDL evidenced by literature data. These results support that RWPC could play a coantioxidant role, similar to that of vitamin C, possibly accounting for their LDL vitamin E sparing effect and their beneficial role in lowering CHD risks.
Dietary fish oil inhibits Δ6‐desaturase activity in vivo
Authors: Raz Amiram , Kamin‐Belsky Nurit , Przedecki Fiorenza , Obukowicz Mark 
Published: May 2007

AbstractLiver Δ6‐desaturase activity was determined in mice which were made deficient in (i) n‐6 and n‐3 polyunsaturated fatty acids (PUFA), (ii) n‐6 PUFA, or (iii) arachidonic acid (AA). Initially, the mice were subjected to two cycles of a fasting (1 d)/refeeding (2–3 d) protocol in which they were refed an essential fatty acid‐deficient (EFAD) diet during the refeeding period. This 1‐wk fasting/refeeding protocol, referred to as F/R EFAD, produced a rapid and substantial decline in tissue n‐3 and n‐6 PUFA and a corresponding increase in n‐9 fatty acids, notably oleic acid and Mead acid (20:3n‐9). Combined liver Δ6‐desaturase/elongase/Δ5‐desaturase activities in vivo were quantified by measuring the conversion of 14C‐linoleic acid (LA) to 14C‐AA in mouse liver. Although F/R EFAD caused, as expected, a substantial decline in liver AA and LA content, the conversion of 14C‐LA to 14C‐AA was the same in these mice as in chow‐fed controls (approximately 33–34%). Subsequent refeeding of F/R EFAD mice with an EFAD diet, supplemented with corn oil, restored tissue n‐6 PUFA levels without altering the conversion of 14C‐LA to 14C‐AA. In contrast, refeeding with an EFAD diet, supplemented with fish oil, inhibited 14C‐LA to 14C‐AA conversion by 78%. Significantly, inhibition of conversion of 14C‐LA to 14C‐AA was maintained in F/R EFAD mice that were subsequently fed an EFAD diet supplemented with a 1:1 mixture of fish oil/corn oil. This latter protocol yielded a unique liver fatty acid composition in which AA was selectively depleted, whereas LA and the n‐3 PUFA were increased. The data suggest that dietary n‐3 C20–22 PUFA negatively regulate the in vivo synthesis of n‐6 PUFA at the level of the Δ6‐desaturase.
Long‐chain polyunsaturated fatty acids influence both β‐ and α‐adrenergic function of rat cardiomyocytes
Authors: Ponsard B. , Durot I. , Fournier A. , Oudot F. , Athias P. , Grynberg A. 
Published: May 2007

AbstractDietary polyunsaturated fatty acids (PUFA) have been reported to lower the incidence of cardiovascular diseases, but neither the mechanisms that determine these protective effects nor the specific influence of n‐3 vs. n‐6 PUFA series has been well established. The purpose of this work was to demonstrate the influence of the membrane long‐chain fatty acid composition on the spontaneous contractile activity and the adrenergic function of rat cardiomyocytes in culture. Cells were grown for 24 h in a standard culture medium and then for 4 d in media that contained either n‐3 (eicosapentaenoic acid and docosahexaenoic acid) or n‐6 (arachidonic acid) PUFA. The n‐6/n‐3 ratio was 1.2 in n‐3 cells compared with 20.1 in n‐6 cells. The basal contractile properties of these cardiomyocytes were not affected by the PUFA phospholipid composition. However, these modifications influenced the adrenoceptor function because the β‐adrenergic stimulation by isoproterenol (10−7 M) induced a positive chronotropic response that was significantly greater in n‐3 cells. Moreover, the chronotropic response to α‐adrenoceptor stimulation by phenylephrine (10−6 M) appeared significantly more pronounced in the n‐3 cells than in the n‐6 cells. However, the parameters related to the inotropic response induced by these agonists did not differ significantly between the two groups of cells. These results suggested that the membrane long‐chain PUFA composition does not influence the basal cardiac contractility and automaticity but is able to modulate the chronotropic function of both α‐ and β‐adrenoceptors.
Peroxisomal metabolism of adrenic acid; No Δ4 desaturase detected in rat liver peroxisomes
Authors: Haugen T. S. , Mimouni V. , Pedersen J. I. , Grav H. J. , Christiansen E. N. 
Published: May 2007

AbstractThe existence of a peroxisomal Δ4 desaturation of 22:4n‐6 and 22:5n‐3 to yield, respectively, 22:5n‐6 and 22:6n‐3 has been questioned. An alternative pathway has been formulated to include microsomal chain elongation and Δ6 desaturation and peroxisomal chain shortening. We incubated [1‐14C]adrenic acid (22:4n‐6) in a system for desaturation (i.e., in the presence of NADH) with purified rat liver peroxisomes. The fatty acids were separated as methyl derivatives by high‐performance liquid chromatography. Four ultraviolet‐absorbing product peaks appeared, three of which contained radioactivity, which we investigated as methyl, trimethylsilyl, and oxazoline derivatives on gas chromatography‐mass spectrometry. In addition to adrenic and arachidonic acids, the product peaks were trans‐enoyl, hydroxy, and keto derivatives of adrenic acid: the three first steps of β‐oxidation cycle. This indicated that the NAD‐dependent dehydrogenase step in the peroxisomal β‐oxidation cycle of adrenic acid was inhibited due to a high concentration of added NADH. Incubation in the presence of NAD instead of NADH reduced radioactivity in the peaks that corresponded to intermediates, while radioactivity in the acid‐soluble fraction increased considerably, consistent with a complete β‐oxidation cycle of adrenic to arachidonic acid. There were no indications of Δ4 desaturation in purified peroxisomes incubated in a standard desaturation system. Instead, adrenic acid as substrate underwent β‐oxidation.