ORAC (oxygen radical absorbance capacity) assay and other methods for the evaluation of antioxidants :: essays research papers

1. IntroductionMost people know or so antioxidants and belive in them as preventers against cell damage, which in the most severe model can cause cancer. Almost all nutritions contain a accepted measurement of antioxidant &8211 both chemical and/or biological. To measure the bodily process and amount of the antioxidants present in a sample, some distinctive but liberal verifications have been established. This paper will give a short overview of the ORAC (type O grouping absorbance cacpacity) assay and compare it with other antioxidant assays.Besides that, the paper introduces some introductory results on antioxidant activity of the prepare Apocynum venetum conducted by the author.Fig. 1 on cover page from 9Table of Contents1. Introduction22. The ORAC assay &8211 a brief introduction43. Biochemical background of antioxidant activity64. Comparison of ORAC with other antioxidant activity assays75. Results in trustworthy research86. Discussion and conclusions9References102. The ORAC assay &8211 a brief introduction2.1 Theoretical backgroundThe oxygen radical absorbance electrical condenser (ORAC) assay is a method for measuring the total antioxidant activity in a biological sample. Biological samples include body fluids of animals and humans (serum, plasma, urine, saliva), plant extracts, agricultural and food products, and pharmaceutical products.6The advantage of the ORAC assay is the wide ramble on of applications as it can be used for both lipophilic and hydrophilic samples and compounds. Besides measuring the total antioxidant capacity, the assay can also qualitatively measure the amount of fast versus slow acting antioxidants in a sample.The principle of the ORAC is based on the following schemeFig. 2 genius order of the ORAC assay10The sample contains a certain amount of compounds with an antioxidant activity. In pissing soluble samples, fluorescein is used as the probe which is protected by the antioxidants.3 After adding a certain amount o f a free radical, the liberation in fluorescence over time is measured until the whole fluorescence is eliminated and the scavenging activity of the antioxidant is vanished. By integrating the area under the kinetic curve relative to the blank, the compactness of all antioxidants present in the sample can be calculated. Trolox, a water soluble tocopherol derivative, is used as a measuring stick to calculate the antioxidant activity of the sample in trolox equivalents (&956mol TE/g).2.2 fluoresceine reactionFluorescein belongs to the group of triphenylmethane dyes with a xanthene expression. Its fluorescence is based on the oxygen withdrawing groups and the intermittend double bounds shifting the wavelength towards the visible light range. Radicals can distubr this structure and erase the fluorescence by destructing one aromatic ring structure as seen in the reaction scheme.