Antioxidant Activity Of Alpha-tocopherol Research Articles

Sulforaphane protects against cell‐mediated LDL oxidation and potentiates the effects of alpha tocopherol

Increased consumption of cruciferous vegetables is associated with health, especially, lower incidence of certain cancers. Broccoli accumulates significant amounts of glucoraphanin, the only dietary source of sulforaphane (SF). There are several studies reporting on SF dependent antioxidant enzyme induction in cell-based, animal human clinical studies that indicate a protective effect of SF against oxidative stress. However, a direct effect of SF on cell-mediated LDL oxidation has not been reported. Oxidized LDL (OxLDL) levels are increased in atherosclerosis and higher levels predict cardiovascular events. In this study, we tested the effects of SF (0.1–10uM) alone and in combination with alpha-tocopherol (AT) on human monocyte derived macrophage (HMDM) mediated LDL oxidation. LDL oxidation was assessed using OxLDL ELISA. Ratio of reduced to oxidized glutathione (GSH:GSSG) was measured. SF (5 uM) caused 40% inhibition of LDL oxidation and potentiated the effects of AT (25uM, 65% inhibition, p<0.001). Furthermore, SF (>1uM) significantly increased GSH:GSSG ratio in HMDM. These studies provide evidence for SF as an antioxidant per se and also a potentiator of the antioxidant activity of AT by increasing cellular GSH:GSSG ratio. Future studies will provide mechanistic insights for these beneficial effects of SF and potential benefits relevant to heart health.

Flavonoids from the flower ofRhododendron yedoense var.Poukhanense and their antioxidant activities

Antioxidant flavonoids have been isolated from the flower of Rhododendron yedoense var. poukhanense. One new flavonoid and three known flavonoids, quercetin-5-O-beta-D-glucopyranoside (1), quercetin (3), and quercitrin (4), were isolated from the butanol and ethyl acetate extracts of the plant. The new flavonoid was identified as myricitrin-5-methyl ether (2). The isolation of these flavonoids from this plant, for the first time, is a valuable finding. The flavonoids were evaluated for their antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH), TBARS (thiobarbituric acid reactive substance) and superoxide anion radical (O2-) in the xanthine/xanthine oxidase assay system. In the DPPH scavenging assay, the IC50 values were 4.5 +/- 0.48 microM for compound 2 and 9.7 +/- 0.29 microM for compound 3, which showed an antioxidant activity approximately 1.5-2 times higher than the antioxidant activity of alpha-tocopherol (9.8 +/- 0.94 microM). Additionally, the antioxidant activities of myricitrin-5-methyl ether (2) (IC50 = 1.7 +/- 0.22 microM) and quercetrin (4) (IC50 = 1.9 +/- 0.63 microM) were higher than that of L-ascorbic acid (IC50 = 7.4 +/- 0.63 microM) when evaluated using a TBARS assay. Compound 2 showed high activity in both the inhibition of xanthine oxidase (1.1 +/- 0.21 mM) and in the activation of superoxide scavenging.

Trapping of the OH Radical by α-Tocopherol: A Theoretical Study

The antioxidant activity of alpha-tocopherol against the damaging hydroxyl radical was analyzed theoretically by hybrid density functional theory, following the direct dynamics method, where the thermal rate constants were calculated using variational transition-state theory with multidimensional tunneling. We found that the OH radical is only slightly or not at all selective, attacking by different mechanisms at several positions of the alpha-tocopherol molecule, giving competitive reactions. The most favorable pathways are the hydrogen abstraction reaction from the phenolic hydrogen and the electrophilic addition onto the aromatic ring. We propose a final rate constant, the sum of the competitive hydrogen abstraction and addition reactions, > or =2.7 x 10(8) M(-1) s(-1) at 298 K, where the hydrogen abstraction reaction represents only 20% of the total OH radical reaction. This result indicates that, molecule by molecule, in an apolar environment, alpha-tocopherol is less effective than coenzyme Q (which presents a rate constant of 6.2 x 10(10) M(-1) s(-1) at 298 K) as a scavenger of OH radicals. It was also found that both mechanisms are not direct but pass through intermediates in the entry channel, with little or no influence on the dynamics of the reactions. The hydrogen abstraction reaction also presents another intermediate in the exit channel, which may have a significant role in preventing the pro-oxidant effects of alpha-tocopherol, although less important than with free radicals other than OH.

Effects of vitamin E supplementation on lipid peroxidation and color retention of salted calf muscle from a diet rich in polyunsaturated fatty acids.

The color of fresh meat is one of the most important quality criteria of raw muscle foods. This red color is principally due to the presence of oxymyoglobin. The present study was undertaken to examine the effect of a diet rich in polyunsaturated fatty acids (PUFA), the addition of NaCl, and the influence of dietary supplementation with vitamin E on calf muscle oxymyoglobin oxidation (color) and lipid peroxidation. Vitamin E was added to the feed at a concentration of 4000 mg/day for 90 days before slaughter. This diet increased the alpha-tocopherol concentration in muscle membrane from 2.6-2.8 to 6.5-7.0 microg/g of fresh weight. It was found that the diet rich in PUFA and, especially, the addition of NaCl increased muscle lipid peroxidation and oxymyoglobin oxidation as indicated by the contents of thiobarbituric acid-reactive substances and substances that impaired color value readings during storage at 4 degrees C. Both undesirable reactions during storage were controlled very efficiently by the presence of a critically high concentration of alpha-tocopherol in the muscle tissues. The findings concerning the antioxidant activity of alpha-tocopherol in this study form additional evidence of its efficient protection against oxidative reactions during storage of muscle tissues and its potential to maintain a high nutritional value in them.

Antioxidant activity of alpha-tocopherol in dopamine containing liposomes: [formula omitted]1, S.N.Kolomeitchuk 1, A.P.Kaplun 1, V.V.Yurasov 2, V.G.Kucheryanu 2, V.I.Shvets 1. 1 M.V.Lomonosov Institute of Fine Chemical Technology, 86 Pr. Vernadskogo, 117571 Moscow, Russia; 2 Institute of General Pathology and Pathophysiology, Academy of Medical Sciences, 125315, 8 Baltiyskaya, Moscow, Russia

Antioxidant activity of alpha-tocopherol in dopamine containing liposomes: [formula omitted]1, S.N.Kolomeitchuk 1, A.P.Kaplun 1, V.V.Yurasov 2, V.G.Kucheryanu 2, V.I.Shvets 1. 1 M.V.Lomonosov Institute of Fine Chemical Technology, 86 Pr. Vernadskogo, 117571 Moscow, Russia; 2 Institute of General Pathology and Pathophysiology, Academy of Medical Sciences, 125315, 8 Baltiyskaya, Moscow, Russia