The BAP test and the global assessment of oxidative stress ... - Medial

1. IntroductionThe blood of Vertebrates contains severalcompounds/activities which are able, takentogether, to oppose the oxidant potential ofoxidant chemical species, like the reactiveoxygen species (ROS) (1).Virtually, any “endogenous” compound (i.e. albumin, transferrin, ceruloplasmin, bilirubin,uric acid, reduced glutathione, etc.) or“exogenous” biomolecule (i. e. tocopherols,carotens, ubiquinol, ascorbate, methionine,flavonoids, polyphenols, etc.) which is able togive equivalent reducing units (e. g. electrons)is able also to block the potential damage ofROS. Indeed, the reactivity of a free radical isjust the result of a lack of electrons (2).Of course, any injury to such “blood barrierto oxidation” – e. g. exposure either toradiations, or xenobiotics or infectious agents –can result in oxidative tissue damage and,therefore, in early aging and in the so-calledoxidative stress related diseases (e. g.atherosclerosis, arterial hypertension, stroke,myocardial infarction, diabetes, arthritis,dementia, colitis, pancreatitis, respiratorydiseases, cancer, infections, etc.) (3).The velocity of these processes can beslowed down not only by specificpharmacotherapies (e. g. antihypertensive orlipid-lowering drugs), but also by modifyingsome lifestyles (e. g. diet, exercise, etc.) and,when indicated, by the intake of compoundswith antioxidant activity (4).However, before any medical intervention,the antioxidant effectiveness of plasma barrierto oxidation should be assessed, in order tolimit the eventual intake of antioxidants only topatients showing a reduced antioxidant plasmaactivity (5). In fact, an uncontrolled intake ofantioxidants has been shown to induce aparadoxical unwanted pro-oxidant action (6,7).Therefore, the assessment of antioxidantactivity of plasma/serum blood is the first stepof any medical intervention aimed to redressthe oxidative balance in oxidative stress relatedconditions.Over the last few years, a number of testsbased on different chemical principles has beenproposed in order to assess the wholeantioxidant activity of plasma or serum blood(5, 8-18).In this subject, one of the most knowexamples of oxidation in Nature is the changeof iron from ferrous to ferric form, as it happenin the generation of the rust. Therefore onecan consider as antioxidant a solution, such theserum/blood plasma, which is able to bringback the iron from its ferric form to the ferrousform.In other words from the merely analyticalpoint of view, the effectiveness of antioxidantplasma barrier can be evaluated by testing itsability to reduce a specific substrate, i. e. byassessing its ability to give oxidant agents (e.g. free radicals) to one or more electrons.For this purpose, several chemicalreducing-oxidizing couples are available. Forinstance, transition metals (i e. iron) exhibitthe property to receive one electron thusshifting from the oxidized state (Fe 3+ ) toreduced state (Fe 2+ ). Such agents can work as“meters” in tests aimed to assess antioxidantpower of biological systems. Indeed, the socalled“plasma antioxidant power” is ultimatelya measure of the reducing or “electron-giving”activity of blood plasma.On the other hand, some compounds sharethe ability to change their absorbance justwhen bound to compounds able to switch fromthe oxidized to reduced state. For instance,some thiocyanates are able to reversibly shiftfrom colored to uncolored derivatives, in thepresence of ferric or ferrous salts, respectively(19). Such “chromogens” can work as excellent“detectors” when coupled with adequate“oxidizing/reducing meters” in a test designedto assess antioxidant activity of biologicalsamples.Indeed, when a ferric salt is dissolved in auncolored solution containing a particularthiocyanate derivative, the resulting solutionbecomes red, as a function of the ferric ionsconcentration. This phenomenon is ascribableto the formation of a complex between ferricsalt and thiocyanate. Further adding of a smallamount of blood plasma will reduce ferric ions5www.fras4evolvo.it