The gradient applied at a flow rate of 1. The identification and quantification were achieved by comparison with retention times of pure phenolics. Scavenging of DPPH radicals. The ethanol solution of the DPPH 2. The mixture was allowed to stand in the dark at room temperature for h before the use. Because ABTS and potassium persulfate reacted stoichiometrically at a ratio of The oxidation of the ABTS commenced immediately, but the absorbance was not maximal and stable until more than 6 h had elapsed.
The radical was stable in this form for more than two days when stored in the dark at room temperature. Solvent blanks were run in each assay. Lipid oxidation assay oxygen consumption assay. The oxygen consumption is related with the total level of lipid oxidation, and therefore, with the formation of both primary and secondary products of oxidation Roedig-Penman and Gordon ; Hopia and Heinonen The relative antioxidative effect of the extract and pure compounds was measured according to Hu and Skibsted The influence of each antioxidant on the initial rate of oxygen consumption, V O2 , was calculated as an antioxidative index Ioxy relative to the rate of oxygen consumption in the absence of the antioxidant:.
Antioxidant activity using Rancimat method. QFE was added to the lard and sunflower oil as a solution in absolute ethanol in concentrations of 0. BHT was used as a comparative sample in a concentration of 0. Citric acid was added as a synergist in 0. The antioxidant activity, expressed as the protection factor PF , was calculated by the following equation:.
The activity of QFE toward secondary products of lipid oxidation was evaluated using the thiobarbituric acid test. Chicken meat was minced, homogenized and divided in the portions of g. The extract 0. All the measurements of the different experiments were performed at least in duplicate.
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The presented data were represented as mean values and statistically analyzed using Microsoft Excel. Reverse phase HPLC combined with electrochemical detection showed that the obtained extract mainly consisted of quercetin The antioxidant activity of the plant extracts depends on the type and polarity of extraction solvent, the isolation procedure and the nature of the antioxidant components in the raw material.
In most cases, the antioxidant properties are related to the presence of phenolic compounds in the extracts Shahidi and Wanasundara ; Jorgenxen ; Quiles et al. In the present study, the dry QFE contained high concentrations of phenolics determined as gallic acid equivalents The high concentration of quercetin in QFE is a prerequisite for a high antioxidant activity of the extract. The antioxidant activity of the plant extract is studied with the determination of its radical scavenging activity, as the latter is considered to be the principle mechanism by which the flavonoids are included in retarding the lipid oxidation Shahidi and Wanasundara ; Bettin et al.
Quercetin, as the main component of the extract, was used as a reference standard component. QFE has the ability to act as a free radical inhibitor, particularly with respect to the peroxy radical, which is the propagator of the autoxidation processes in fats and oils. The ABTS assay is a method used for the evaluation of the total antioxidant capacity of single compounds and complex mixtures of various plants Miller et al.
The results showed that QFE Higher TEAC values indicated that the sample had stronger antioxidant activity. From the results it was concluded that QFE could be used as an effective antioxidant for retarding the first step of lipid oxidation and formation of free radicals.
Antioxidant properties of medicinal plants in food. [Doctoral dissertation]
Since lipid oxidation is a complex multistep process, it is of interest to investigate at which step of lipid oxidation, QFE will influence the process. For this purpose, different methods were used in the present work for the evaluation of its antioxidant activity. QFE was analyzed using the electrochemical method of oxygen consumption, which gave more precise information about the ability of the antioxidant to interrupt the chain reaction in propagation of lipid oxidation.
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Information about antioxidative effects of the investigated extract and other water-soluble antioxidants was obtained by the values of antioxidative index Ioxy Table 2. The Ioxy of QFE 0. Antioxidant activity in model food systems.
A comparative study of the antioxidative action of the derived flavonoid product and BHT as reference was carried out with sunflower oil and lard. Sunflower oil with a peroxide value of 3. The extract exhibited a high antioxidant activity in lard, even higher than BHT which was one of the most used synthetic antioxidant in lipid systems Buxiang and Fukuhara The antioxidant activity was improved by increasing the concentration of QFE and the plant extract could be presumed as a good substitute.
The probable reason for that might be the presence of tocopherols in sunflower oil Laubli and Bruttel , which were natural antioxidants and preserved the oil itself. In order to improve the oxidative stability of sunflower oil and lard, the synergistic effect of QFE with citric acid 0. The results are shown in Table 4. Particularly in lard, a synergistic effect of the mixture of QFE 0.
In contrast, the increase of PF in sunflower oil was rather small. Similar synergistic effects were observed by Banaias et al. The quantitative evaluation of the antioxidant capacity of the flavonoid compounds in QFE against lipid peroxidation was determined applying the TBARS assay. The antioxidant activity of QFE was tested in a real food system using cooked chicken meat. The extract was added to the meat homogenate in two concentrations 0. The high antioxidant scavenging activity as well as the retarding of lipid oxidation in food systems lard, sunflower oil and chicken meat showed the undisputable antioxidant activity of studied flavonoid-rich extract from Sophora japonica L.
However, the use of quercetin containing extract in food requires toxicity studies and sensory acceptance. Further research is required to address this concern and validate the beneficial effects and safety of using QFE. The results obtained as well as the information about the toxicity of the synthetic antioxidants used in food products showed the possibility of using the natural extracts such as QFE as alternative sources for antioxidant additives in food processing and generally outline the possibility for their application in food technology.
Total Phenolics-method for analysis of musts and wines. New York: John Wiley; Optimising the use of phenolic compounds in foods.
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Cambridge: Woodhead Publishing; A critical apparaisal of the use of the antioxidant capacity TEAC assay in defining optimal antioxidant structure. Food Chem. Supercritical carbon dioxide extraction of antioxidant fractions from selected Lamiaceae herbs and their antioxidant capacity. Innov Food Sci Emerg Technol. Bahchevanska S and Koleva I. A study on the autohydrolysis of rutin to quercetin from Sophora japonica blossoms.
Bahchevanska S and Mihaylova D. Investigation of possibility for stabilization of different natural lipids and oils through the addition of plant extract from Sophora japonica, Journal of International Scientific Publications.
The effect of primary antioxidants and synergists of the activity of plant extracts in lard. Phenols and metals in sugar-cane spirits. Quantitative analysis and effect on radical formation and radical scavenging. Eur Food Res Technol. The effect of dietary oregano essential oil on lipid oxidation in raw and cooked chicken during refrigerated storage.
Meat Sci. Buxiang S and Fukuhara M. Effect of coadministration of BHT, BHA and flavonoides an the activation of mutagens and drug-metabolising enzymes in mice.source
Antioxidant activity of Piper sarmentosum Roxb. and its effect on the degradation of frying oils
Lipid oxidation inhibiting capacities of blackseed essential oil and rosemary extract. The syntactic function of age, in general. The event was very close to an over- simplified designation of communal, and a pretext for such staff members are likely to impose censorship.
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