Do these methods measure both enzymatic and nonenzymatic antioxidant potential of plant samples or only antioxidant potential derived from nonenzymatic systems?
Enzymes per se do not directly add to the antioxidant potential, they merely catalyze the transfer of electrons from small molecules (NAD(P)H, GSH, ascorbate, etc. If you have a large concentration fo enzymes present but no reducing equivalents available, the enzymes will be inactive. At the end of the day, your antioxidant potential will be some type of sum of the concentrations of the different small molecule antioxidants present, with some contributing more to the overall antioxidant potential than others.
Hi,
the most commonly used antioxidant method is ABTS radical cation generated by enzymes or chemical reactions. It can be dissolved in aqueous and organic media, in which antioxidant activity can be measured due to its hydrophillic and lipophillic nature of the compound samples.
The ferric reducing antioxidant power (FRAP) is based on the reduction of ferroin analogue that is Fe3+ to Fe2+ by antioxidants in acidic medium.This test is nonresponsive to -SH group antioxidants.
Thank you for the answer, but I need to know what type of antioxidant can I measure by those methods.
I have found that ABTS can measure only antioxidant potential derived from low weight compounds, like e.g. phenols.
But I was wonder - if I have a plant tissue homogenate in which the antioxidant enzymes are in active forms, then using ABTS assay I in fact measure a TOTAL antioxidant potential of the sample, i.e. from enzymes + nonenzymatic antioxidants. In my opinion this is because, on the example of Halliwell-Asada cycle: ABTS radical will be scavenged by ascorbic acid, which will be in turn recover by the enzymes of aforementioned cycle, and so on. In case of FRAP assay low pH will stop activities of enzymes, so by using this reaction the final result is depends only on non enzymatic antioxidants.
Whether I want to ask this reasoning has any sense or am I wrong?
Enzymes per se do not directly add to the antioxidant potential, they merely catalyze the transfer of electrons from small molecules (NAD(P)H, GSH, ascorbate, etc. If you have a large concentration fo enzymes present but no reducing equivalents available, the enzymes will be inactive. At the end of the day, your antioxidant potential will be some type of sum of the concentrations of the different small molecule antioxidants present, with some contributing more to the overall antioxidant potential than others.
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