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Reaction kinetics of betanin and its aglycone betanidin towards peroxyl radicals generated from the azo-initiated oxidation of methyl linoleate in methanol, and of a heterogeneous aqueous/soybean phosphatidylcholine liposomal system, were studied by monitoring formation of linoleic acid hydroperoxides and consumption of the pigments. Betanin was a weak retarder in methanol, and an effective chain breaking antioxidant in the liposomal model, indicating that kinetic solvent effects and partition in lipid bilayers may affect its activity. Betanidin behaved as a chain terminating antioxidant in both models. Kinetic parameters characterizing peroxyl radical-scavenging activity showed that betanidin was more effective than betanin, in terms of both radical-scavenging rate constant and stoichiometric factor, with effectiveness of the same order as vitamin E under comparable conditions. Products identified by spectrophotometric and HPLC techniques indicated reaction of the glucose-substituted monophenol and ortho-diphenol moieties of betanin and betanidin, respectively, and suggested mechanisms of the antioxidant activity. Either betanin or betanidin incorporated in liposomes with -tocopherol, had additive effects, supporting partition of the pigments in the bilayer and lipoperoxyl radical reduction.

Fifteen beta-thalassemia intermedia patients, not requiring chronic transfusional therapy, were monitored in order to check their antioxidant status, and the lipid oxidation products in plasma, LDL, and erythrocytes before and during a 9-month oral treatment with 600 mg/day vitamin E. The low level of vitamin E, and high level of malondialdehyde in plasma clearly tended to normalize after three months (P < .001), and were quite similar to control after six months. The abnormally low level of vitamin E in LDL and the four times higher than control basal level of conjugated dienes (LDL-CD), were not modified after three months of treatment. Significant changes of LDL-VE (P < .05) and of the basal LDL-CD (P < .001) were evident after six months. LDL-VE was within the normal range after nine months, whereas LDL-CD still appeared twice as higher than control. Plasma vitamin A, ascorbate, beta-carotene, and lycopene increased markedly at the end of the trial (P < .005). The level of vitamin E in red blood cells was normalized after six months of supplementation. A decrease of the baseline value of conjugated dienes was observed after nine months, although it remained 1.4-fold higher than control. The RBC count and hematocrit appeared higher at the end of the trial (P < .05 and P < .001, respectively). The hemoglobin value did not show variations. A shift to normal of the resistance of erythrocytes to osmotic lysis was observed. Our findings provide evidence that an oral treatment with vitamin E improves the antioxidant/oxidant balance in plasma, LDL particles, and red blood cells, and counteracts lipid peroxidation processes in beta-thalassemia intermedia patients.

This work investigated the oxidative injury to human red blood cells (RBCs) by the exposure to exogenous malondialdehyde (MDA), in a physiological environment. When a 10% RBC suspension was incubated in autologous plasma, in the presence of 50 microM MDA, 30% of MDA entered into the cells. A time-course study showed that MDA caused early (30-120 min) and delayed (3-18 h) effects. MDA caused a fast depletion of reduced glutathione, and loss of the glucose-6-phosphate dehydrogenase activity, followed by a decrease of HbO2. Accumulation of methemoglobin, and formation of small amounts of hemichrome were later evident. Also, an HbO2-derived fluorescent product was measured in the membrane. The redox unbalance was followed by structural and functional damage to the membrane, evident as the formation of conjugated diene lipid hydroperoxides, concurrent with a sharp accumulation of MDA, consumption of membrane vitamin E, and egress of K+ ions. SDS--PAGE of membrane proteins showed formation of high molecular weight aggregates. In spite of the marked oxidative alterations, the incubation plasma prevented a substantial hemolysis, even after a 18 h incubation. On the contrary, the exposure of RBCs to 50 microM MDA in glucose-containing phosphate saline buffer, resulted in a 16% hemolysis within 6 h. These results indicate that the exposure to MDA causes a rapid intracellular oxidative stress and potentiates oxidative cascades on RBCs, resulting in their dysfunction.

Lipid peroxidation products, lipid antioxidants, and hematologic and blood chemistry changes were evaluated in plasma of patients after acute burning injury involving 10% (n=8), 20% (n=8), and 40% (n=5) of total body surface area (TBSA), 24 h after burning (baseline) up to 30 days after. Markedly increased plasma levels of malondialdehyde (MDA) were observed at baseline in all patients, according to the extent of the injury, then the values declined progressively. However, levels of MDA remained above normal up to 30 days even in less injured patients. On the other hand, the plasma level of conjugated diene lipid hydroperoxides was only slightly higher than control at the baseline, then dropped under the control value in all patients. Cholesterol showed a marked fall at baseline, followed by a rapidly progressive decrease, indicating a massive loss of circulating lipids by the acute thermal injury. Because of such an extensive and rapidly spreading oxidative degradation of lipids, decomposition of conjugated diene hydroperoxides, produced in early stages of the peroxidation process, occurs, so these compounds cannot be a suitable index to value lipid oxidation in burned patients. Aldehydic products of lipid peroxidation act as endotoxins, causing damage to various tissues and organs. Damage to liver and decrease of erythrocyte survival were assessed by increased plasma levels of asparate and alanine transaminases, within 7-15 days after injury, and by a decreased number of red blood cells, which remained under the normal value at 30 days. A marked decrease of lipid antioxidants, beta-carotene, vitamin A and vitamin E was observed at baseline. The level of beta-carotene remained low in all patients at the end of the 30-day observation. A complete recovery of vitamin A did not occur at 30 days post-burn, even in the patients with 10% of burned TBSA. Plasma levels of vitamin E decreased significantly in 1-7 days after burn in all patients, but these levels increased thereafter, with almost total recovery at 30 days. These data show evidence of a marked, long-lasting oxidant/antioxidant imbalance in burned patients, in accordance with the severity of the injury, which is also reflected as systemic oxidant stress.