Quantitative measurement of the total, peroxyl radical‐trapping antioxidant capability of human blood plasma by controlled peroxidation

Abstract

Plasma obtained from fasted humans has been analysed for total radical-trapping antioxidant content by subjecting it to controlled peroxidation using the thermal decomposition of water-soluble azobis (2-amidinopropane hydrochloride) at 37°C to produce peroxyl radicals at a known, steady rate. It is found that the total radical-trapping antioxidant content is rather similar for the 7 subjects that have been tested and, furthermore, it is lo-20-times larger than the effect attributable to vitamin E alone. Although it is shown that urate and ascorbate augment the contribution from vitamin E, their contributions (21-34 and O-2%, respectively) still leave 57-73% of the total antioxidant content unaccounted for. Evidence is presented to show that this previously unrecognized large reserve of antioxidant capacity is attributable to the plasma proteins.

Neuroprotection for ischemic stroke: Past, present and future

“…It is the plasma's major antioxidant, antagonizing both endogenous and exogenous sources of oxidative stress (Wayner et al, 1985;Halliwell, 1988). At least three mechanisms are responsible for albumin's potent antioxidant action: a) its reactive cysteine-34 thiol moiety; b) its ability to bind redox-active transition metals, in particular copper ions, thereby inhibiting copper iondependent lipid peroxidation and formation of the highly reactive hydroxyl radical species (Halliwell, 1988); and c) its binding of amphipathic species such as fatty acids and heme, which may participate in injurious redox reactions.…”

Is there an unidentified defence mechanism against infection in human plasma?

“…Briefly, constant production of peroxyl radicals by ABAP (2,2'-azobis [2-amidinopropane] hydrochloride) is followed by luminol-enhanced chemiluminescence. The time for which the added test sample extinguishes the reaction is directly proportional to the peroxyl radical-trapping antioxidant capacity of the sample [11,12]. TRAP is thus expressed as micromoles of peroxyl radicals trapped by one litre of the sample.…”

“…In addition to direct measurement of TRAP (TRAPmeas), calculated TRAP (TRAPcalc) was derived from the concentrations of individually measured antioxidants in plasma with experimentally determined stoichiometric factors [11,12]: For protein SH-groups the stoichiometric factor was 0.4, for ascorbic acid 0.7, for uric acid and for tocopherol 2.0. Thus TRAPcalc = 2.0 X (tocopherol concentration) + 2.0 X (uric acid) + 0.7 x (ascorbic acid) + 0.4 X (SH-groups).…”

Neurotoxicity of hemoglobin in cortical cell culture

“…These results should be extended to situations in vivo with some caution. During the course of these experiments, neurons were deprived of the usual antioxidant defenses normally present in extracellular fluid, e.g., plasma or cerebrospinal fluid [25,27]. The presence of these constituents may counterbalance the loss of intracellular central nervous system (CNS)…”