Insights on Antioxidant Assays for Biological Samples Based on the Reduction of Copper Complexes—The Importance of Analytical Conditions

Abstract

Total antioxidant capacity assays are recognized as instrumental to establish antioxidant status of biological samples, however the varying experimental conditions result in conclusions that may not be transposable to other settings. After selection of the complexing agent, reagent addition order, buffer type and concentration, copper reducing assays were adapted to a high-throughput scheme and validated using model biological antioxidant compounds of ascorbic acid, Trolox (a soluble analogue of vitamin E), uric acid and glutathione. A critical comparison was made based on real samples including NIST-909c human serum certified sample, and five study samples. The validated method provided linear range up to 100 µM Trolox, (limit of detection 2.3 µM; limit of quantification 7.7 µM) with recovery results above 85% and precision <5%. The validated developed method with an increased sensitivity is a sound choice for assessment of TAC in serum samples.

Yield, physicochemical, and antioxidant properties of Atlantic salmon visceral hydrolysate: Comparison of lactic acid bacterial fermentation with Flavourzyme proteolysis and formic acid treatment

“…It is possible that the presence of lactate and formate in LA and FA‐hydrolysates, respectively are responsible for interference with the FRAP assay. Marques et al reported that buffer systems significantly influence results in a Cu(III)‐reducing assay (Marques, Magalhães, Tóth, & Segundo, ).…”

Determination of Some Biochemical Parameters in Streptozotocin-Induced Diabetic Albino Rats Pre-Treated and Post-Treated with Vernonia amygdalina and Gongronema latifolium Extracts

“…Total antioxidant capacity (TAC) is the measure of the amount of free radicals scavenged by a test solution [35], and it is used to evaluate the antioxidant capacity of biological samples [36]. Total antioxidant capacity (TAC) includes both enzymatic antioxidants, such as catalase, and non-enzymatic antioxidants, such as ascorbic acid [37].Studies on total antioxidant capacity in albino rats administered with V. amygdalina and G. latifolium extracts following diabetic induction is scarce.…”

Myoglobin microplate assay to evaluate prevention of protein peroxidation

“…In fact, the interaction of thiols with reactive radicals can generate thiyl radicals which have a pro-oxidant effect, especially in iron-rich environments, which is the case of iron atoms release during Mb autoxidation [27]. However, reduced glutathione represents a powerful endogenous antioxidant as demonstrated by other antioxidant assays that applied different mechanisms of reaction such as metal reduction [28] and scavenging of multiple reactive oxygen species [29].…”