Thiobarbituric acids, detection

Analytical Techniques. Sorbic acid and potassium sorbate are assayed titrimetricaHy (51). The quantitative analysis of sorbic acid in food or beverages, which may require solvent extraction or steam distillation (52,53), employs various techniques. The two classical methods are both spectrophotometric (54—56). In the ultraviolet method, the prepared sample is acidified and the sorbic acid is measured at 250 260 nm. In the colorimetric method, the sorbic acid in the prepared sample is oxidized and then reacts with thiobarbituric acid the complex is measured at - 530 nm. Chromatographic techniques are also used for the analysis of sorbic acid. High pressure Hquid chromatography with ultraviolet detection is used to separate and quantify sorbic acid from other ultraviolet-absorbing species (57—59). Sorbic acid in food extracts is deterrnined by gas chromatography with flame ionization detection (60—62). 

Evidence that oxidized lipids play a role in the pathogenesis of RA comes from studies demonstrating the presence of lipid products arising from radical attack in rheumatoid synovial fluid. This is consistent with oxidation reactions occurring locally in the joint. Lipid peroxidation products that react with thiobarbituric acid (TBARs) have been detected in rheumatoid knee-joint synovial fluid (Rowley et /., 1984). In addition, the... 

Drugs such as 2-thiobarbituric acid are oxidized in the presence of iodide mediators. In aqueous media, an electroio-dination process occurs and the resulting voltammetric signal allows quantitative determination [190]. A similar methodology with a limit of detection at ca. 40 gM level has been developed for barbiturates [191]. Also, catechin as a model system for polyphenols was studied in the presence of an iodide redox mediator [192]. 

Cardo PP, Lombardo C, Gatti R (1985) A simple detection of sialic acid storage disorders by urinary free and total sialic acid determinations. Clin Chim Acta 150 129-135 Denny PC, Denny PA, Allerton SE (1983) Determination of sialic acid using 2-thiobarbituric acid in the absence of hazardous sodium arsenite. Clin Chim Acta 131 333-336... 

Thiobarbituric acid (TBA) assays detection in lipids, 547-564 Malondialdehyde. see Malonaldehyde Malt, (3-glucan quantitation, 751 Mandarin orange oil. see Citrus oils Orange... 

The aldehydic products from the autoxidation of PUFA have always been of interest, since the thiobarbituric acid (TBA) test detects malonaldehyde (or malonaldehyde precursors) with considerable sensitivity (76-78) and since malonaldehyde itself is mutagenic (H). More recently, Esterbauer and his coworkers have shown that 4-hydroxy-2-alkenals, and particularly 4-hydroxy-2-nonenal, are extremely cytotoxic (76f77,7Q). 

Asakawa, T. and Matsushita, S. (1979) Thiobarbituric acid test for detecting lipid peroxides, Lipids 14, 401-406. 

The thiobarbituric acid (TBA) test was proposed over 40 years ago and is now one of the most extensively used methods to detect oxidative deterioration of fat-containing foods (41). During lipid oxidation, malonaldehyde (MA), a minor component of fatty acids with 3 or more double bonds, is formed as a result of the degradation of polyunsaturated fatty acids. It is usually used as an indicator of the lipid oxidation process, both for the early appearance as oxidation occurs and for the sensitivity of the analytical method (42). In this assay, the MA is reacted with thiobarbituric acid (TBA) to form a pink MA-TBA complex that is measured spectrophotometrically at its absorption maximum at 530-535 nm (Figure 2) (9,43,44). The extent of oxidation is reported as the TBA value and is expressed as milligrams... 

Consequently, in addition to hydroperoxides, a lot of secondary oxidized lipidic compounds, mainly short-chain aldehydes, may appear and represent late markers of lipid peroxidation. As an example, malondialdehyde (MDA, Fig. 6) is known to be the most abundant lipid peroxidation aldehyde whose determination by 2-thiobarbituric acid (TBA) is one ofthe most common assays in lipid peroxidation studies [20]. However, it can be noticed that the TBA assay method [21] is not specific of MDA titration since it also can detect a variety of peroxides and secondary degradation products of lipid peroxidation called... 

The most popular method involves 2-thiobarbituric acid (TBA) two molecules of 2-thiobarbituric acid are condensed with malonaldehyde. The emergent chromogen — the two tautomeric structures of the red TBA-malonaldehyde adduct — is determined at 532 nm, and also often at 450 nm, to determine aUcenals and aUcanals, respectively. The qualitative Kreis test was based on a similar principle it involved detection of the epihydrine aldehyde — a tautomeric malondialdehyde — in a color reaction with resorcine or phloroglucinol. The popularity of the TBA test stems from a correlation between the results and sensory evaluations. Paradoxically, this is related to the most important drawback of the TBA technique — its lack of specificity. In addition to the reaction with malonaldehyde, TBA forms compounds of identical color with other aldehydes and ketones, products of aldehyde interaction with nitrogen compounds, and also with saccharides, ascorbic acid, creatine, creatinine, trimethylamine oxide, trimethylamine, proteins, and amino acids. For this reason, the TBA test may even be treated as a proteolysis indicator (Kolakowska and Deutry, 1983). Recently, TBA-reactive substances (TEARS) were introduced, primarily to stress that the reaction involves hydroperoxides in addition to aldehydes. Due to the nonspecificity of the TEARS test, its results reflect the rancidity of food better than other conventional methods, especially off-flavor, which is caused by volatiles from lipids as well as being affected by products of lipids interaction with nitrogenous compounds. 

Whang, K. 1999. High perfonnance liquid chromatography (HPLC) detection of malonalde-hyde-thiobarbituric acid (MA-TBA) complex in ground pork, J. Food Sci. Nutr., 4(3),... 

Products of Lipid Peroxide Decomposition. In view of the potential problems with direct lipid analysis, a simpler and more sensitive assay, the detection of thiobarbituric acid-reacting materials (TBARM), was used to detect DPE injury to membranes... 

There are few mechanistic details on the formation and structures of the DNA oxidation products in the Cr + Red + O2 + DNA systems. Reduction of Cr(VI) with GSH or ascorbate induced simultaneous formation of comparable amounts of single-strand breaks and abasic sites in isolated DNA (376, 377, 381). Malondialdehyde was detected (by reaction with thiobarbituric acid) as an oxidation product of DNA or 2-deoxyribose in the Cr + Red + O2 systems (Red = GSH or ascorbate) (379). These features correspond to DNA oxidation by hydrogen abstraction at C4 atom of the deoxyribose moiety (405,406). More detailed studies of DNA oxidation mechanisms were performed using a model Cr(V) complex, [CrVO(ehba)2]- (Section III.C.4). 

In the presence of iron, fragmentation of both the cyclopentane and endoperoxide rings can give rise to malondialdehyde (MDA), an ubiquitous product of lipid peroxidation [53-55]. MDA is the intended target of the thiobarbituric acid reactive substances (TEARS) assay commonly used to measure Upid peroxidation, although a broad spectrum of other lipid electrophiles are also detected by this assay. 

Thus, in the absence of sulfur(II) compounds, a constant absorbance of iodine is recorded when the HPLC system is supplied with azide ions from the mobile phase and iodine solution from postcolumn reagents. Moreover, a decrease in the signal is observed when a sulfur(II) compound is present in the chromatographic band. This is attributed to iodine consumption in the iodine-azide reaction and is detected as a negative peak at 350 nm. The peak is quantitatively dependent on the amount of the sulfur(II) compound present. Fig. 2 shows the chromatogram obtained for 2-thiobarbituric acid. 

The chemistry and analysis of sialic acids have been reviewed. Picomole quantities of sialic acids have been measured by the fluorescence produced by the periodate-oxidized acid in the thiobarbituric acid reaction. " Contamination of the sialic acids with 2-deoxy-D-eryt/iro-pentose (derived from cellular material) could be detected by a downfield shift of the excitation maximum. Fluorescent derivatives are also produced when free sialic acids react with pyridoxamine, a procedure that compares favourably with the thiobarbituric acid reaction for determining sialic acids. Keto-acids e.g. pyruvic acid) interfere with the determination, but 2-deoxy-D-arabmo-hexose and 2-deoxy-D-c/-ytliro-pentose do not. A nonfading chromophore is produced when DMSO is used instead of n-butanol in the thiobarbituric acid ssay for sialic acids. A new histochemical method for the visualization and identification of unmodified or 0-acylated sialic acids has been reported. ... 

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