ABTS can dissolved in both water and organic solvent. for ABTS assay we can used trolox catechin and ascorbic acid as standard, but mostly ascorbic acid used as standard, and why. why ABTS assy is performed if we already performed DPPH assay, bec in DPPH aasay also ascorbic acid mostly used as standard, so what is the reason performing both the assay for single plant extract
In order to evaluate the antioxidant activity of the extracts, the ABTS test can be used to evaluate the discoloration of radical cations and measure the inhibitory power of free radicals.
ABTS (2,2’-azinobis [3-ethylbenzothiazoline-6-sulfonic acid])is a chemical compound. This substance is usually used as a substrate for peroxidase enzymes and multimolecular copper oxidases.
DPPH )1,1-Diphenyl-2-picryl-hydrazyl،(is an unstable free radical that can receive an electron or a hydrogen radical and become stable, and in the presence of substances with antioxidant properties, it changes color by receiving an electron. Its color change from purple to yellow is the basis for checking its antioxidant properties.
The antioxidant ascorbic acid is an electron donor. In fact, in the oxidation reaction, which has an oxidizing agent and a reducing agent, this antioxidant plays the reducing role, that is, its antioxidant capacity depends on its reducing ability. The amount of standard reducing power of ascorbic acid in measuring DPPH inhibition by ascorbic acid is immediate.
The evaluation method of antioxidant capacity with DPPH radical is based on the reduction of DPPH free radical by antioxidants in the absence of other free radicals in the environment, and the result of this process causes the creation of color in the environment, the intensity of which can be measured with a spectrometer is taking.
The term antioxidant is commonly used in areas related to biochemistry. In other areas we use the term inhibitors of radical processes. Therefore, the test for antioxidant activity should be performed under physiological conditions, namely in aqueous solutions at neutral pH or in lipids. DPPH test does not fit these requirements, but can be used to estimate the activity of inhibitors, e.g. in food production. ABTS has been developed to measure the total antioxidant capacity (TAC), e.g. of plant extracts. Trolox is water soluble analog of vitamin E, natural antioxidant capable to scavenge two radicals. ABTS perfectly works for polyphenols. Theoretically, TACs measured in Trolox or ascorbic acid equivalents should be the same.
DPPH is not natural radical. The values from DPPH and ABTS assays can't be compared. The only advantage of DPPH is the simplicity of the assay.
- Badges
- Science topic