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Antioxidants: Various Methods of Evaluation

Sudhakar, Singh (2004) Antioxidants: Various Methods of Evaluation. Masters thesis, University of Mysore.

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Abstract

This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Thesis (Masters)
Additional Information: <p align="justify">The two fundamental elements of human life, Food and oxygen, are involved in intricately conflicting interactions. Oxidation of fuel molecules through the process of respiration is source of energy for survival and activity. However, significant fraction of oxygen utilized by the body is incompletely reduced. Such partially reduced forms of oxygen and their derivatives are highly reactive pro-oxidants, and are known as Reactive Oxygen Species (ROS), which include free radicals and non-radical derivative of oxygen. The powerful reactivity of ROS can cause functional damage to biological systems, triggering a number of degenerative diseases like mutagenesis, carcinogenesis, circulatory disturbances, and aging. Highly reactive oxygen molecules and oxygen radicals are generated from the triplet oxygen (the native form) by excitation or reduction. Oxygen thus activated is called active oxygen and is important in the deterioration of food as well as in other biological effects of oxygen. ROS is a collective term that includes oxygen-centered radicals (superoxide and hydroxyl) and some non-radical derivatives of oxygen (hydrogen peroxide, singlet oxygen and hypochlorous acid). The source of free radicals may be endogenous (through various electron transport chains, enzymes etc.) or exogenous (ionizing radiations, nvironmental pollutants, physiological factors etc.). To combat the harmful effect of ROS, a wide range of antioxidants have been recommended to be consumed. These antioxidants are added in the form of dietary antioxidants to our food systems. In general, antioxidants are defined as any substance that, when present at low concentrations compared to those of an oxidisable substrate, significantly delays or prevents oxidation of that substrates. These antioxidants can be of exogenous (various dietary components) as well as endogenous (enzymes, like SOD and catalase) origin. To determine the efficacy of natural antioxidants for food preservation or protection, against oxidative damage, to avoid deleterious changes and loss of commercial and nutritional value,it is necessary to develop rapid methods for determining the antioxidant capacity in various components of food and other products. This serves as a useful tool for making selection among different species, varieties, maturation degree and culture conditions, in order to obtain high content of natural antioxidants in foods. The strategies adopted for determining the antioxidant capacity is by monitoring the inhibition of oxidation of a suitable substrate and measuring the extent of oxidation by chemical, instrumental or sensory methods. The various in vitro methods used for antioxidant assays are (1) DPPH (2,3, -diphenyl-1-picrylhydrazyl) assay (2) TEAC (Trolox Equivalent Antioxidant Capacity) assay or ABTS ([2,2-azinobis- (3-ethylbenzothiazoline-6-sulphonic acid)] assay (3) DMPD (N, N-dimethylp-phenylene-diamine) assay (4) ORAC (Oxygen Radical Absorbance Capacity) assay (5) FRAP (Ferric Reducing Ability of Plasma) assay/Ferric Reducing Antioxidant Power) (6) TRAP (Total Radical Trapping Antioxidant Parameter) Assay (7) PCL Photochemiluminescence) Assay (8) Thiobarbituric Acid Reactive Substances (TBARS) Assay (9) the carotene-linoleic acid system (10) Phosphomolybdate Assay. The various commonly used in vivo methods used for antioxidant assays are (1) Cyclic voltammetry method for Low Molecular Weight Antioxidants (LMWA) (2) Crocin based assay (3) Endogenous peroxidase activity estimation (4).Determination of superoxide dismutase and glutathione peroxidase (5a) Conjugated diene assay (5b) Lipid peroxide (PD) assay (5c) Linoleyl hydroperoxide (L-OOH) and linoelyl hydroxide (L-OH) assay (6)Dichlorofluorescin-diacetate (DCFH-DA) based assay and (7) TOSC (total oxyradical scavenging capacity) assay. The wide variation in the methodology and instrumentation used for antioxidant assay obviously reflect their in-built advantages and limitations for assaying the antioxidant capacity of variety of components/compounds. For e.g., the PCL method is able to analyze antioxidant activity in nanomolar range within short time in contrast to other methods, which detect antioxidant activity in micromolar range with longer time. Also, only few methods make the use of physiological radicals in the assay procedure. Thus, in general it may not be possible to transfer the results from these tests to the processes in the biological systems. However, the results of these methods only give an idea on the protective efficacy of various ANTIOXIDANTS. Due to the differences in the test systems, it is strongly recommended to assess the antioxidant potential of any product/compound by a minimum of two methods depending upon the antioxidant potential and perhaps on the origin of the substance.</p>
Uncontrolled Keywords: antioxidants evaluation
Subjects: 600 Technology > 08 Food technology > 32 Antioxidants
600 Technology > 08 Food technology > 01 Analysis
Divisions: Human Resource Development
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 26 Feb 2007
Last Modified: 28 Dec 2011 09:26
URI: http://ir.cftri.com/id/eprint/408

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