Colorimetric Determination of Sulfoxy Radicals and Sulfoxy Radical Scavenging-Based Antioxidant Activity.

Sulfoxy radicals (SORs) are oxygen- and sulfur-containing species such as SO, SO, and SO. They can be physiologically generated by S(IV) autoxidation with transition metal catalysis. Due to their harmful effects, the detection of both SORs and their scavengers are important.

Biomarkers of Oxidative Stress and Antioxidant Defense.

A number of reactive oxygen and nitrogen species are produced during normal metabolism in human body. These species can be both radical and non-radical and have varying degrees of reactivity. Although they have some important functions in the human body, such as contributing to signal transmission and the immune system, their presence must be balanced by the antioxidant defense system.

Sulfate radical formation by Cr(III) activation of peroxydisulfate - Diphenylcarbazide spectrophotometric determination of sulfate radical and its scavenging activity.

Even though sulfate anion radical (SO) is a very reactive oxidant used in advanced oxidation processes, a reliably selective and simple colorimetric method for determining this radical can hardly be found. Peroxydisulfate (SO) or peroxymonosulfate (HSO) can be activated with transition metal ions to produce SO. We have discovered that Cr(III) can be an activator for persulfate, generating Cr(VI) along with SO.

CUPRAC colorimetric and electroanalytical methods determining antioxidant activity based on prevention of oxidative DNA damage.

An unbalanced excess of oxygen/nitrogen species (ROS/RNS) can give oxidative hazard to DNA and other biomacromolecules under oxidative stress conditions. While the 'comet' assay for measuring DNA damage is neither specific nor practical, monitoring oxidative changes on individual DNA bases and other oxidation products needs highly specialized equipment and operators. Thus, we developed a modified CUPRAC (cupric ion reducing antioxidant capacity) colorimetric method to determine the average total damage on DNA produced by Fenton oxidation, taking advantage of the fact that the degradation products of DNA but not the original macromolecule is CUPRAC-responsive.

Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins.

Development of easy, practical, and low-cost spectrophotometric methods is required for the selective determination of phenolic antioxidants in the presence of other similar substances. As electron transfer (ET)-based total antioxidant capacity (TAC) assays generally measure the reducing ability of antioxidant compounds, thiols and phenols cannot be differentiated since they are both responsive to the probe reagent. In this study, three of the most common TAC determination methods, namely cupric ion reducing antioxidant capacity (CUPRAC), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt/trolox equivalent antioxidant capacity (ABTS/TEAC), and ferric reducing antioxidant power (FRAP), were tested for the assay of phenolics in the presence of selected thiol and protein compounds.

A colourimetric sensor for the simultaneous determination of oxidative status and antioxidant activity on the same membrane: N,N-dimethyl-p-phenylene diamine (DMPD) on Nafion.

A colourimetric sensor capable of simultaneously measuring oxidative status (OS) in terms of the hazard produced by reactive oxygen species (ROS) and antioxidant activity (AOA) in regard to ROS-scavenging ability of antioxidant compounds was developed. The coloured cationic semi-quinone derivatives, caused by ROS oxidative degradation of N,N-dimethyl-p-phenylene diamine hydrochloride (DMPD) in pH 5.7 acetate-buffered medium, were formed in solution and immobilized on a perfluorosulfonate-based Nafion membrane.