Antioxidant Activity Of Trolox Research Articles

Substrate and TBARS variability in a multi‐phase oxidation system

The thiobarbituric acid reactive substances (TBARS) assay is widely used to measure antioxidant activity in the presence of lipid substrates such as linoleic acid (LA). In one version of this assay, LA is oxidized with and without antioxidant in a multi‐phase system in which LA lies over the surface of the aqueous layer of catalyst and antioxidant solution, with dissolved and atmospheric oxygen. Results from this assay showed low precision and therefore we conducted a systematic study to identify possible sources of variability including: order of addition of reactants; pre‐formed peroxides in LA (as precursors of TBARS); and the effect of different concentrations of added antioxidant, Trolox. These investigations showed that all contributed to variability of both formation of oxidation products and the antioxidant activity of Trolox. Furthermore, through the use of LA with pre‐formed peroxides removed, it was discovered that antioxidant activities reported in other studies using this system were most likely not due to the protective effect of antioxidant against formation of primary oxidation products. Rather, the antioxidant is likely to interfere with the radical scission of pre‐formed peroxides, resulting in lower TBARS.Practical applications: The results obtained from the TBARS assay have been used to interpret the potential antioxidant value of compounds added to lipid‐containing food products, such as in oil and meat. Alternatively, the TBARS assay has been used to assess multiple compounds or extracts to rank their effectiveness as antioxidants, thus selecting the most active ones for further study. In both cases, pre‐formed peroxides in the system may not be routinely measured. The results from this study suggest that pre‐formed peroxides may have a large impact on the results of antioxidant studies when TBARS are the measure of oxidation. Therefore, further research in other systems is necessary to ensure that robust antioxidant measurements are being performed.TBARS variability: absorbance values at 532 nm for different batches of linoleic acid. Absorbance values show TBARS variability in a multi‐phase oxidation system in measuring antioxidant activity of 250 and 1000 µM Trolox.

Novel Trolox derivatives as antioxidant: A DFT investigation

In this paper the antioxidant activity of Trolox derivatives were investigated by density function theory and polarization continuum model as solvent model in order to propose the novel derivatives with higher antioxidant activity from a theoretical viewpoint. The effects of various ortho and meta substituents on the reaction enthalpies of antioxidant mechanisms of Trolox were investigated. Also the effect of reducing the number of atoms in the heterocyclic ring and effect of replacing the oxygen heteroatom of Trolox with other heteroatoms on the antioxidant activity of Trolox were evaluated. Results show that the NH2, OH and NHMe substituents in meta and ortho positions decrease the BDE and IP values and also increase the antioxidant activity of Trolox from the theoretical viewpoint. The derivatives e, c and d with NH, S and Se instead of O have higher antioxidant activity from the theoretical viewpoint. Obtained results show that reducing the number of atom in the heterocyclic ring (derivatives a and b) decrease the BDE and IP values and also increase the antioxidant activity of Trolox from the theoretical viewpoint. The linear dependencies between BDE of OH bond and IP values of studied Trolox derivatives and corresponding EHOMO and R(O-H) values can be useful to propose novel derivatives with higher antioxidant activity from the theoretical viewpoint.

Comparison in vitro of Antioxidant Activity between Fifteen Campanula Species (Bellflower) from Palestinian Flora

Background: The natural antioxidant products in the plant kingdom play an important role in the healthy life style and reduce the risk for various chronic diseases.Objective: The objective of this study was to investigate different antioxidant pharmacological property of methanol extract for fifteen species of Campanula plant from Palestinian flora. Methods: The antioxidant activity of fifteen Campanula species growing wildly in Palestine were studied using 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity and their antioxidant activity was compared to Trolox antioxidant activity. Results: The results clearly demonstrate a very high antioxidant activity of the Campanula sulphurea and Campanula sidoniensis and they showed almost the same antioxidant activity of Trolox. The other twelve species extracts also exhibited excellent antioxidant activity in DPPH radical scavenging activity in comparison with trolox standard. Conclusion: Methanol extract of Campanula can be valuable for treatment of different diseases and could be used as a possible new source of natural antioxidants in the food, nutraceuticals, pharmaceuticals and cosmetic industry.

Tuning of the pro‐oxidant and antioxidant activity of trolox through the controlled release from biodegradable poly(trolox ester) polymers

In a variety of biomedical applications (e.g., tissue engineering, drug delivery, etc.), the role of a bioactive material is to serve as a platform by which one can modulate the cellular response into a desired role. Of the methods by which one may achieve this control (e.g., shape, structure, binding, growth factor release), the control of the cellular redox state has been under evaluated. Ideally, the ability to tune the redox state of a cell provides an additional level of control over a variety of cellular responses including, cell differentiation, proliferation, and apoptosis. Yet, in order to achieve such control, it is important to know both the overall oxidative status of the cell and what molecular targets are being oxidized. In this work, poly (trolox ester) nanoparticles were evaluated for their ability to either inhibit or induce cellular oxidative stress in a dose-dependent fashion. This polymer delivery form possessed a unique ability to suppress protein oxidation, a feature not seen in the free drug form, emphasizing the advantage of the delivery/dosage formulation has upon regulating cellular response.

Role of reverse micelles on lipid oxidation in bulk oils: impact of phospholipids on antioxidant activity of α-tocopherol and Trolox

Phospholipids self-assemble in bulk oils to form structures such as reverse micelles that can alter the microenvironment where chemical degradation reactions occur, such as lipid oxidation. In this study, we examined the influence of phospholipid reverse micelles on the activity of non-polar (α-tocopherol) and polar (Trolox) antioxidants in stripped soybean oil (SSO). Reverse micelles were formed by adding 1000 μM 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) to SSO. The addition of DOPC reverse micelles had a prooxidant effect, shortening the lag phase of SSO at 55 °C. DOPC improved the activity of low α-tocopherol or Trolox concentrations (10 μM) but decreased the activity of high concentrations (100 μM). Hydrophilic Trolox had better antioxidant activity than hydrophobic α-tocopherol. Fluorescence steady state and lifetime decay studies suggests that differences in the antioxidant activity of Trolox and α-tocopherol could be due to differences in their physical location in DOPC reverse micelles. These results will improve our understanding and control of lipid oxidation in bulk oils.

Reducing Antioxidant Capacity Evaluated by Means of Controlled Potential Electrolysis

AbstractAn analytical method suitable for an antioxidant sensor is presented following the response of these substances to an extensive oxidation imposed by electrochemical means. The electrochemical assay simulates the action of a reactive oxygen species (ROS) by means of electrolyses carried out at a potential which is settled at the formal potential of the ROS. The antioxidant activities of trolox and ascorbic, gallic and caffeic acids and of mixtures of these antioxidants were estimated from the charge required for the complete oxidation of the antioxidants from assays where the oxidative attack by O2 and by O2.− were simulated.

New insights into the antioxidant activity of Trolox in o/w emulsions

The antioxidant activity of Trolox was investigated in emulsions containing different emulsifiers, and decreased in the order Brij 58 > CTAB > SDS. Two degradation products were isolated and identified as Trolox quinone and a keto-derivative. In addition to the stability of Trolox, the effects of the degradation products on lipid oxidation were investigated. In emulsions with SDS, the quinone and the keto-derivative contributed to the overall pro-oxidant effect of Trolox, whereas they had no effect in emulsions containing CTAB or Brij 58. It was concluded that the microenvironment at the o/w interface has a marked influence on the antioxidant and pro-oxidant effects of Trolox and its degradation products via molecular interactions and by affecting its molecular mobility.

Influence of hydroxypropyl-β-cyclodextrin on the photostability and antiradical activity of Trolox

Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a derivative of vitamin E, can undergo photolysis upon UV irradiation. In the present study the photodegradation kinetics of Trolox were thus investigated in different systems in the absence and in the presence of titanium dioxide, a physical sunscreen present in several cosmetic products, that can act as photocatalyst. In all the considered media Trolox degraded under UVB light following pseudo-zero order kinetics, probably by a mechanism of photooxidation. The rate of Trolox photodegradation was lower in O/W emulsions than in aqueous solution and in gel; furthermore it was significantly influenced by the presence of TiO2. Aiming to increase Trolox stability, it was complexed with hydroxypropyl-β-cyclodextrin: the inclusion complex was characterized by phase solubility studies, spectrophotometry and differential scanning calorimetry. The irradiation experiments indicated that complexation with hydroxypropyl-β-cyclodextrin was effective in reducing the photodegradation rate of Trolox. Moreover the host molecule favored the uptake of Trolox into the porcine skin, as shown by in vitro permeation studies. Nevertheless the assay of peroxidation, based on the reaction of malondialdehyde with thiobarbituric acid, indicated that the antioxidant activity of Trolox was maintained even after inclusion in cyclodextrin.

Antioxidant activity of 2,6-dimethyl-3,5-dialkoxycarbonyl-1,4-dihydropyridines in metal-ion catalyzed lipid peroxidation

Antioxidants with 1,4-dihydropyridine structure were investigated as a less harmful alternative to synthetic phenolic antioxidants in liposomes under conditions simulating food storage. The antioxidant activities (AOA) of 2,6-dimethyl-3,5-dialkoxycarbonyl-1,4-dihydropyridines possessing various side chain length alkyls (CH<sub>3</sub> - C<sub>16</sub>H<sub>33</sub>) in ester moiety were tested in transition metal-ion catalyzed liposome peroxidation and compared with AOA of Trolox™ and Probucol™. The compounds with C<sub>2</sub>H<sub>5 </sub>- C<sub>4</sub>H<sub>9</sub> residues in the 3,5-position ester moieties exert the most pronounced AOA. The AOA of tested compounds is associated with their ability to incorporate into liposomes.

Effect of pH on Antioxidant Activity of α-Tocopherol and Trolox in Oil-in-Water Emulsions

The pH had a more significant effect on the antioxidant activity of Trolox than α-tocopherol in corn oil emulsified with Tween 20 at 60 °C. Although with increasing pH the oxidative stability of corn oil emulsions decreased, the antioxidant activity of α-tocopherol increased. Initially, Trolox and α-tocopherol were similar in inhibiting hydroperoxide formation with or without phosphate buffers at pH 3−7, but at later stages α-tocopherol was more effective than Trolox at pH 3, 4, 5, and 7 but not at pH 6. In contrast, α-tocopherol inhibited hexanal formation better than Trolox during the entire oxidation period. Trolox was more stable than α-tocopherol in bulk corn oil but less stable in Tween 20 solutions at different pH. Both antioxidants in Tween 20 solutions were most stable at pH 3 and least stable at pH 7. Although more Trolox partitioned into the oil phase and the oil−water interfaces at pH 3−4, its antioxidant activity was lower than at pH 5−6. The overall antioxidant activities of α-tocopherol and...

Membrane peroxidation: Inhibiting effects of water- soluble antioxidants on phospholipids of different charge types

Quantitative kinetic methods of autoxidation are used to determine the antioxidant activities of two water-soluble antioxidants of the chromanol type, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) and 6-hydroxy-2,5,7,8- tetramethyl-2- N, N, N-trimethylethanaminium methylbenzene-sulfonate (MDL 73404), during free radical peroxidation of phospholipid membranes of different charge types. The stoichiometric factor (n) for peroxyl radical trapping for both Trolox and MDL 73404 was found to be 2. Trolox was found to partition partially, approximately 20%, into the lipid phase of liposomes. The antioxidant activity of Trolox during peroxidation of membranes determined by measurements of the absolute rate constant for inhibition of oxygen uptake,k inh, was found to vary with the membrane surface charge that is controlled by variation in pH. When peroxidation is initiated in the lipid phase by azo- bis-2,4-dimethylvaleronitrile (ADVN), using a typical zwitterionic liposome, dilinoleoylphosphatidyl choline (DLPC), the k inh was found to be 2.98 × 10 3 M −1s −1. The k inh of Trolox increased approximately 2-fold for membranes that have positive surface, including DLPC at pH 4, DLPC containing stearylamine at pH 7, and for a membrane of dimyristoylphosphatidic acid containing linoleic acid (DMPA/LA). Conversely, Trolox does not inhibit peroxidation of negatively charged dilinoleoylphosphatidyl glycerol (DLPG) at pH 7–11. Studies made of the positively charged MDL 73404 show that its antioxidant activity using DLPC and DLPG is pH dependent. Trolox inhibits the peroxidations of DLPC initiated in the aqueous phase by azo- bis(2-amidinopropane·HCl)(ABAP) at pH 4 or 7. However, Trolox does not inhibit the peroxidation of DLPG at pH 7. The different antioxidant activities of Trolox and MDL 73404 are rationalized in terms of a peroxyl-radical diffusion model and specific charge interactions between antioxidants and membrane surface.