Kinetics of Oxidation and Antioxidation Processes in Biological Solutions Observed by NMR Relaxation (original) (raw)
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Observation of Antioxidants Activity using NMR Relaxation Measurements
ACTA PHYSICA POLONICA A, 2018
Formation of free radicals in biological solutions leads to the changes in water protons relaxation times. Therefore, NMR relaxation measurements were used to investigate kinetics of oxidation processes induced by the addition, in low amounts, of hydrogen peroxide (H2O2q to aqueous protein solution and to blood serum. The measured relaxation times were not stable over time because of the progressive formation of free radicals and their damaging action to the protein structure. The addition of antioxidants (ascorbic acid, gallic acid etc.) changed the relaxation time courses due to free radical scavenging. Similar time courses, thus anti-oxidant actions, were observed in various blood serum without antioxidant additive. Moreover, the observed kinetics of spin-lattice relaxation time (T1q depended on several factors, such as: structure and concentration of protein solutions and activity and concentration of the added antioxidants.
NMR Relaxation Measurements as a Tool for Observation of Oxidative Processes
ACTA PHYSICA POLONICA A, 2016
Water proton relaxation times, T1 and T2, were measured to assess the kinetics of the oxidative processes in biological samples. The oxidation in aqueous solutions of albumins was promoted by an addition of 3% hydrogen peroxide (H2O2). Immediately following this addition a sharp exponential decrease of both relaxation times was observed. As we confirmed experimentally, the time course of relaxation depended on several essential factors like structure and the concentration of proteins and also the presence of antioxidants added to solution. In experiments with protein solutions containing a small amount of ascorbic acid, after reaching a minimum, relaxation time increased towards the initial (pre-addition H2O2) values. We conclude that this T1 and T2 recovery is a consequence of the presence of antioxidants and may be used to evaluate its action. This study demonstrates that nuclear magnetic resonance (NMR) relaxation measurements may be useful in evaluating free radicals reactions and antioxidants capacity.
Antioxidant Activity of Medicinal Tea Evidenced by Electron Spin Resonance
2015
Electron spin resonance (ESR) studies were carried out on 5 types of organic tea cultivated in Romania: Mentha piperita, Hypericum perforatum, Achillea millefolium, Rhamnus frangula, Calendula officinalis and the results compared with commercial Twinnings black tea. In function of tea type, spin centers like Mn bounded and unbounded by proteins, Fe and Cu was evidenced. Dry tea leaves show additional sharp line attributed to semiquinone radical which disappeared in tea drinks. The origin of the spin species in analyzed tea leaves and drinks are defined and discussed. The evaluation of antioxidant capacity of analyzed tea drinks was based on measuring the changes of ESR spectrum of radicals as a result of their interaction with antioxidants. The Mentha piperita and Hypericum perforatum tea exhibit an important scavenging activity. In the case of Mentha piperita the scavenging activity is comparable with that of black tea.
Metabolomics
A protocol for determination of oxidation susceptibility of serum lipids based on proton nuclear magnetic resonance (1H NMR) spectroscopy is presented and compared to the commonly used spectrophotometric method. Even though there are methodological differences between these two methods, the NMR-based oxidation susceptibility correlates well (r 2 = 0.73) with the lag time determined spectrophotometrically. In addition to the oxidizability of serum lipids, the NMR method provides also information about the lipid profile. The NMR oxidation assay was applied to the chocolate study including fasting serum samples (n = 45) from subjects who had consumed white (WC), dark (DC) or high-polyphenol chocolate (HPC) daily for 3 weeks. The oxidation susceptibility of serum lipids decreased in the HPC group, and there was a significant difference between the WC and HPC groups (P = 0.031). According to the random forest analysis, the consumption of the HPC chocolate induced changes to the amounts of HDL, phosphatidylcholine, sphingomyelin, and nervonic, docosahexaenoic and myristic acids. Furthermore, arachidonic, docosahexaenoic, docosapentaenoic and palmitic acids, gamma-glutamyl transferase, hemoglobin, HDL, phosphatidylcholine and choline containing phospholipids explained about 60% of the oxidation susceptibility values.
Agricultural Sciences, 2013
Coffees and teas are beverages that are both exceptionally rich in antioxidant molecules, and are also both associated with beneficial health effects. Thus although the quality characteristics of these beverages are conventionally assessed on the basis of their sensory properties, their antioxidant contents represent an additional and increasingly valued attribute of quality based on their contributions to healthy diets. Both beverages are prepared by hot water extraction of a pure plant-derived product, and thus their compositions can potentially change quite rapidly as a result of oxidation in contact with air. Oxidative processes often proceed via free radical intermediates, and sometimes also result in the formation of stable radical endproducts; thus EPR spectroscopy is a convenient technique for investigating some of the various free radical reactions that occur in these beverages. This paper reviews progress that has been made in elucidating free radical processes that occur during the preparation and storage of coffees and teas, and the results are discussed in terms of quality criteria of the beverages.
An electron paramagnetic resonance study of antioxidant properties of alcoholic beverages
Food Chemistry, 2012
The antioxidant properties of samples of different kinds of commercially available alcoholic beverages were investigated by electron paramagnetic resonance (EPR) spectroscopy. This analytical technique is chiefly designed to enable accurate detection of free radicals. The determination of antioxidant activity by the EPR method is conducted by measuring the changes of the intensity of the EPR spectrum of stable radicals, which results from their interaction with antioxidants. Antioxidant capacity of alcoholic beverages samples was assessed with the use of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH Å). The highest antioxidant activity was found in red wines, followed by a blend of wine and brandy and then by whiskies, whereas plain vodkas and gin showed negative values of antioxidant activity. From our studies it can be concluded that the value of antioxidant capacity depends on the polyphenolic content, the time and method of ageing, as well as on the flavour and colour additives.
2008
Tea is a powerful antioxidant beverage consumed in many soft drinks today. The characterization of its antioxidative properties during and especially after its preparation procedure, inclusive their long time stabilities, is an important tool for the soft drink industry. The antioxidative capacity and re- activity are two parameters which gives a compre- hensive description of the antioxidant properties. Both parameters are integrated in the antioxidative power AP, a 2D factor. The AP of the green tea bev- erage exceeds all other types of tea. Black tea has an AP which is six times lower than that of green tea.
A study of the stability of antioxidant activity of green tea extract powder with vitamin C
Pharmacy Education, 2023
Background: Green tea contains Epigallocatechin gallate (EGCG), the highest antioxidant activity. EGCG is an unstable compound due to degradation. Vitamin C is thought to be able to regenerate EGCG radicals into normal forms and increase green tea's antioxidant activity. Objective: The aim of this research was to determine the effect of adding vitamin C in maintaining the stability of the antioxidant activity of green tea. Method: This research was carried out by using UV-Vis spectrophotometry to determine the rate of decreasing antioxidant activity at 0 hours, six hours, and 24 hours by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Result: IC 50 values of green tea before and after the addition of vitamin C were obtained at 147.53 ppm and 97.75 ppm, respectively. The degradation rate of green tea before and after the addition of vitamin C was 0.4228 %/hour and 0.3231 %/hour, respectively. Conclusion: The antioxidant activity of green tea with vitamin C is greater than without vitamin C addition. The degradation rate of green tea with vitamin C is smaller than green tea only, so the authors suggest the addition of vitamin C to green tea extract powder products to increase the stability of its antioxidant activity.
Comparative study of antioxidant potential of tea with and without additives
Indian journal of physiology and pharmacology, 2000
Oxidative damage is one of the many mechanism leading to chronic diseases. Therefore interest is growing in the protection afforded by antioxidant nutrients against free radical reactions. More recently, the attention has shifted to polyphenols. Polyphenols are secondary plant metabolites occurring widely in plant food. They possess outstanding antioxidant properties, suggesting a possible protective role in man. Tea (Camellia sinensis) is a widely consumed beverage throughout the world containing polyphenols more than 35% of its dry weight. In the present work we have investigated the effect of tea without milk, tea with milk and lemon tea on the serum lipid peroxidation level (as a parameter of free radical generation). The results show that there were significant decrease in serum lipid peroxidation (Malonaldehyde) level half hour after ingestion of lemon tea and tea without milk which tends to normalize with increase in time. This decrease is much significant in case of lemon te...