Thiobarbituric acid reactive substances TEARS

Thiobarbituric Acid-Reactive Substance (TEARS) Assay... 

Antioxidative effect. Tea, administered orally to rats, decreased the thiobarbituric acid reactive substances (TEARS) contents... 

Halliwell et al. (55) have described a model that uses hydroxyl radicals generated from Fenton reaction to degrade 2-deoxy-D-ribose. The decomposed products of deoxyribose are 2-thiobarbituric acid-reactive substances (TEARS). If the antioxidant present in the system scavenges hydroxyl radicals generated, deoxyribose is protected and the amount of TEARS produced is less. 

Moderately thermally oxidized soybean oil (130°C, air flow-through) of peroxide value (PV) = 75 mEq 02/kg diet (compared with the control of 9.5 Eq 02/kg diet) was fed to rats for 40 days (Eder and Kirchgessner, 1999). The study showed no adverse effects on liver, heart, kidney, or adipose tissue FA composition, and even a reduction in the osmotic fragility of erythrocytes and hepatic lipogenesis. However, the moderately oxidized oil slightly reduced the vitamin E status in the tissues. A slightly increased susceptibility of LDL to lipid peroxidation, and an increased concentration of thiobarbituric acid reactive substances (TEARS) in LDL, were also observed. 

Since the use of tobacco is a chronic process, the effects of an aqueous extract of STE in rats following low-dose exposure were examined. Female Sprague-Dawley rats were treated orally with 25mg STE/kg every other day for 105 days. The effects of subchronic treatment of STE on hepatic microsomal and mitochondrial lipid peroxidation were assessed. Urinary excretion of the four lipid metabolites malondialdehyde, formaldehyde, acetaldehyde, and acetone was monitored by HPLC, with maximum increases being observed between 60 and 75 days of treatment. The assessment of lipid peroxidation was based on the formation of thiobarbituric acid-reactive substances (TEARS) over the 105 days of the study. 

Lipid peroxidation was measured as thiobarbituric acid reactive substances (TEARS). The concentration of a-tocopherol or TRF was 5pM. Values are mean SE from five experiments. 

In rats given spearmint tea ad libitum for 30 days, liver enzyme changes were observed. Decreases in superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) and an increase in thiobarbituric acid-reactive substance (TEARS) were noted (Akdogan et al. 2004b). 

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. 

In vitro, the oxidative capability of rat microglia is double that of thioglycollate-elicited macrophages, and both granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-ip significantly increased the thiobarbituric acid-reactive substances (TEARS) level by 36% (P <0.003) and 34% (P <0.05), respectively (Smith et al. 1998). 

This assay is basically used to appoint the lipid oxidation. It is an older test for receiving the oxidation status of fats spectrophotometricaUy. Thereby the aldehydes, which are generated by the autoxi-dation of unsaturated fatty acids, are converted into red or yellow colorimeters with TEA. Eut it is also used for the determination of the potency of antioxidants with thiobarbituric acid reactive substances (TEARS). Thereby the antioxidant activity is measmed by the inhibition of the lipid oxidation. It concerns the spectrophotometric detection of malonic aldehyde, one of the secondary lipid peroxidation products, which generates a pink pigment with TEA (Ruberto et al., 2000 Varda-Unlii etal.,2003). 

FIGURE 6. Inhibition of in vivo protein (carbonyls) and lipid peroxidation (MDA by HPLC) and of in vitro lipid peroxidation (TBARS-NADPH) in liver of guinea pigs fed during five weeks with high vitamin C diets versus those fed a diet just enough to avoid scurvy (33 mg ascorbic acid/kg). MDA = true malondialdehyde TEARS = thiobarbituric acid-reactive substances. TEARS were measured after 90 min in the presence of 0.2 mM FeS04, 5 mM ADP, and 1 mM NADPH. Reproduced with permission from Free Rad. Biol. Med. 17 105-115 (Barja et al., 1994). 

The ability of the pyrone molecnles to protect liposomes from photochanicaUy-induced oxidative damage was investigated using the thiobarbituric acid reactive substances (TEARS) assay [5]. This assay is based on the detection of malondial-dehyde (76), an end prodnct of lipid peroxidation commonly used as a biomarker for cell damage (Sect. 1.2.2.3, Scheme 14) [6]. Malondialdehyde (76) reacts with thiobarbituric acid (124), when heated under acidic conditions, to form a conjugated adduct, 125, which absorbs strongly at 532 nm (Scheme 4.2). Thus treatment of a sample of interest with 124, followed by comparison of the absorption with that of a standard curve generated from known quantities of 76, allows the concentration of malondialdehyde (76) to be determined colorimetrically (see Sect 6.3.2 for further details). 

Measurement of Hydroperoxides and 2-Thiobarbituric Acid Reactive Substances (TEARS)... 

Figure 1. Effects of papain and actinase E hydrolysate concentration on antioxidant activity as shown by relative changes in the 2-thiobarbituric acid reactive substances (TEARS).

---