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The discovery of the implication of free radicals in the etiology of many diseases has led to increased interest in functional food that contain many different dietary phytonutrients, including antioxidants. One of the most important issues in the natural antioxidants analysis is determination of their antioxidant activity. The total antioxidant activity of some natural and commercial juices has been evaluated using a new TLC method that involves reaction between DPPH (2,2-diphenyl-1-picrylhydrazyl) and the antioxidants from juices. The antioxidant activity, expressed in vitamin C units, was determined on the basis of a calibration plot, peak area being a function of vitamin C concentration.

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Abstract  

Three commonly used medicinal plants, e.g., Adhatoda vasica, Cassia fistula, and Withania somnifera grown in two contrasting environmental conditions, namely from copper mining site and from control site corresponding to soil not contaminated with Cu, to understand correlations between high Cu bioaccumulation in medicinal plants on their antioxidant activities. Concentrations of some essential metals, e.g., Cr, Mn, Fe, Cu, Zn, and Se in the leaves of these plants were measured by instrumental neutron activation analysis. The Cu levels in the samples from mining site were in the range of 32.6 to 57.2 mg/kg, which were 5–7 folds higher than the control samples, while Cr levels were about 2-folds higher in the mining site. Speciation studies of Cr revealed negligible content of toxic hexavalent Cr. Antioxidant assay of these plants from both the sampling sites, measured as total phenolic content, total flavonoid content, 2,2′-diphenyl-1-picrylhydrazyl, free radical scavenging ability, and chelating ability with ferrous ions exhibited maximum activity for A. vasica, while that of W. somnifera was minimum. However, the variations in the antioxidant activities for each medicinal plant species from mining site and control site did not reveal significant differences.

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Holoptelea integrifolia (Sanskrit: chirivilva, Hindi: chilbil, family: Ulmaceae) is a large deciduous tree, growing up to 18 m tall, distributed throughout the greater part of India up to an altitude of 2000 ft. It has grey bark, covered with blisters, peeling in corky scales on old trees. The plant has several medicinal properties such as antiinflammatory, anthelmintic, and antidiabetic activity. The present work was taken up with a view to lay down standards which will contribute significantly to the quality control of the medicinally useful Holoptelea species. Till date, there is no comparative phytochemical and antioxidant literature available of this traditionally valuable drug. Biomarkers such as stigmasterol, olenolic acid, ursolic acid, betulin, and lupeol were estimated through high-performance thin-layer chromatography (HPTLC) method, and it was found maximum in Behraich plant sample. The bark of Behraich’s sample shows strong antioxidant activity (2,2-diphenyl-2-picrylhydrazyl [DPPH] assay). It suggests secondary metabolites present in H. integrifolia having antioxidant effects, which indicate their effectiveness in diseases caused by overproduction of free radicals. Over all, these comparative data provide a suitable criteria to differentiate the stem barks of the above four Holoptelea barks of different places from India and open a new vista for the exploitation of these species for the development of herbal formulations.

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biochemistry 2003 Cumby, N., Zhong, Y., Naczk, M. & Shahidi, F. (2008): Antioxidant activity and water

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Variation of antioxidant activity was measured for differently prepared extracts of pressed residues (marc) from red wine making and production of blackcurrant and redcurrant juice. On the basis of previous tests ethanol and water were chosen as suitable solvents for preparing phenolic extracts from selected samples. Antioxidant activity was also measured for commercially available standards of the anthocyanins present in grapes and red- and blackcurrants, for example malvidin 3-glucoside (Mv3G), cyanidin 3-glucoside (Cy3G), delphinidin 3-glucoside (Dp3G), peonidin 3-glucoside (Pe3G), and petunidin 3-glucoside (Pt3G). Each standard and a mixture of all standards (concentration 250 μg mL −1 ) were analyzed. Two different analytical methods were used, spectrophotometry and TLC. In both methods DPPH was used as a source of stable free radicals with which components with antioxidant activity react. The strongest antioxidant activity was found for Cy3G, then for Pe3G and Mv3G, and the lowest was for Pt3G and Dp3G (both methods). Relatively high antioxidant activity was determined for all samples. The most effective was blackcurrant extract prepared with 70% aqueous ethanol and the least effective were redcurrant extracts. Correlations between TLC and spectrophotometry were calculated for standards and for extracts. The results showed that the methods correlated well for pure standards ( r = 0.979) whereas for crude extracts the correlation was slightly lower (0.857) but still acceptable.Press residues from red wine making and from production of black-currant and redcurrant juice are rich sources of phenolic antioxidants and so could be used as natural antioxidants in the food industry.

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Acta Biologica Hungarica
Authors: Huan Zhang, Pan Wang, Ai-Jun Zhang, Xuan Li, Ji-Hong Zhang, Qi-Lian Qin, and Yi-Jun Wu

. 9. Sakanaka , S. , Tachibana , Y. , Ishihara , N. , Juneja , L. J. ( 2004 ) Antioxidant activity of egg-yolk protein hydrolysates in a linoleic acid oxidation system . Food Chem. 86 , 99

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Ultraviolet—visible (UV—vis) spectrometry, electron paramagnetic resonance spectroscopy, high-performance liquid chromatography, and thin-layer chromatography were used for the evaluation of the antioxidant activity of natural samples. All the methods used free radicals to determine antioxidant capacity and standard antioxidant compounds, usually Trolox or vitamin C, to express the results. In this study, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) methods for the determination of the antioxidant activity of some wines previously separated by high-performance thin-layer chromatography (HPTLC) are statistically compared. The antioxidant activities were quantified based on the calibration curves obtained after elution under the same chromatographic conditions of different quantities of Trolox. Also, the reaction time was established to be between 10 and 30 min. The results show that the values found for DPPH and ABTS assays are well correlated, the values obtained in the case of ABTS being higher. The ABTS method is more sensitive than DPPH assay and is more useful than DPPH assay in the determination of the antioxidant activity of natural samples. In the case of real samples tested, the antioxidant activities decrease in the order red wines, rose wines, and white wines.

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Acta Alimentaria
Authors: E. Ivanišová, K. Meňhartová, M. Terentjeva, L. Godočíková, J. Árvay, and M. Kačániová

References Aidoo , E. ( 2015 ): Studies on the cytotoxicity and antioxidant activity of tea kombucha . MSc. Dissertation

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Acta Alimentaria
Authors: A. Alberti, R. Amorati, M. Campredon, M. Lucarini, D. Macciantelli, and G. Pedulli

Burton, G.W., Doba, T., Gabe, E.J., Hughes, L., Lee, F.L., Prasad, L. & Ingold, K.U. (1985): Autoxidation of biological molecules. 4. Maximizing the antioxidant activity of phenols. J. Am. Chem. Soc. , 107 , 7053

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1200 Yen, G. C., Duh, P. D. & Tsai, C. L. (1993): Relationship between antioxidant activity and maturity of peanut hulls. J. agric. Fd Chem. , 41 , 67

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