Martin Grootveld

Allopurinol and oxypurinol are hydroxyl radical scavengers

Allopurinol is a scavenger of the highly reactive hydroxyl radical (k 2 approx. 109 M−1s−1). One product of attack of hydroxyl radical upon allopurinol is oxypurinol, which is a major metabolite of allopurinol. Oxypurinol is a better hydroxyl radical scavenger than is allopurinol (k 2 approx. 4 × 109 M−1s−1) and it also reacts with the myeloperoxidase‐derived oxidant hypochlorous acid. Hence the protective actions of allopurinol against reperfusion damage after hypoxia need not be entirely due to xanthine oxidase inhibition.

The measurement of free radical reactions in humans: Some thoughts for future experimentation

The question as to whether free radical reactions are a major cause of tissue injury in human disease, or merely an accompaniment to such injury, is very difficult to answer because of lack of adequate experimental techniques. New techniques that are becoming available are discussed, with specific reference to their use in humans.

Biologically significant scavenging of the myeloperoxidase-derived oxidant hypochlorous acid by ascorbic acid Implications for antioxidant protection in the inflamed rheumatoid joint

Ascorbic acid, at physiological concentrations, can scavenge the myeloperoxidase‐derived oxidant hypochlorous acid at rates sufficient to protect α1‐antiprotease against inactivation by this molecule. The rapid depletion of ascorbic acid at sites of inflammation, as in the inflamed rheumatoid joint, may therefore facilitate proteolytic damage.

An investigation of the abnormal metabolic status of synovial fluid from patients with rheumatoid arthritis by high field proton nuclear magnetic resonance spectroscopy.

The 1H Hahn spin‐echo NMR profiles of rheumatoid synovial fluids have been investigated and compared with those of matched serum samples. In addition to markedly elevated lactate and diminished glucose concentrations, inflammatory synovial fluids contained (i) substantially lower levels of NMR‐detectable chylomicron‐ and very‐low‐density‐lipoprotein‐associated triacylglycerols which appear to have a shortened mean chain‐length, and (ii) high concentrations of ketone bodies (predominantly 3‐d‐hydroxybutyrate), relative to those of corresponding paired serum samples. These observations confirm the abnormal metabolic status of the inflamed rheumatoid joint and provide evidence for an increased utilisation of lipids for fuel therein.

A comparative evaluation of the metabolic profiles of normal and inflammatory knee-joint synovial fluids by high resolution proton NMR spectroscopy

High resolution 1H NMR spectroscopy has been employed to investigate the metabolic profile of heatlhy human knee‐joint synovial fluid (SF) and the biochemical data acquired have been compared with those of matched serum, and inflammatory knee‐joint SF samples. Results obtained indicate that the healthy human knee‐joint has a hypoxic status (high lactate level when expressed relative to that of paired serum) that is milder than that of the inflamed human knee‐joint. Moreover, normal SF differs from that of inflammatory SF in that it contains little or no NMR‐detectable lipoprotein‐associated fatty acids and ‘acute‐phase’ glycoproteins, an observation reflecting the limited passage of these macromolecules from plasma into the synovial space in healthy subjects.

Action of Uric Acid, Allopurinol and Oxypurinol on the Myeloperoxidase-Derived Oxidant Hypochlorous Acid

Both oxypurinol and uric acid react with the myeloperoxidase-derived oxidant hypochlorous acid at physiological pH, and they can protect the elastase-inhibitory capacity of human alpha 1-antiprotease against inactivation by hypochlorous acid. Allopurinol does not protect alpha 1-antiprotease, possibly because the redox potential of allopurinol at physiological pH is too positive to permit oxidation by hypochlorous acid.

Control of oxidative damage in rheumatoid arthritis by gold(I)-thiolate drugs

The roles of anti-arthritic gold(I)-thiolate drugs such as disodium aurothiomalate (Myocrisin) in the modulation or promotion of oxygen radical-mediated oxidative damage in vivo are reviewed. In particular, the precise molecular mechanisms by which these novel second-line agents exert their therapeutic effects are discussed in terms of (i) the direct and indirect control of enzymes involved in the generation or scavenging of reactive oxygen species (ROS) such as superoxide ion, hydrogen peroxide and hydroxyl radical, (ii) the protection of proteins and relevant enzyme systems against attack by ROS and (iii) their direct involvement in the production (at appropriate target sites) or scavenging of ROS in vivo. In addition, the role of the orally-effective gold(I)-phosphine complex auranofin in the control of oxidative damage in rheumatoid arthritis is also discussed.

The detection of irradiated foodstuffs

Abstract The development of effective test systems for detecting the irradiation of foodstuffs is an essential requirement for the establishment of legislative control and consumer choice. Treatment of foodstuffs with ionizing radiation initially generates extremely reactive free radical species (hydroxyl radicals, hydrated electrons or hydrogen atoms for foodstuffs consisting mainly of water) which cause small, but detectable, chemical changes. This review describes recent advances in the assessment of the irradiation status of foods by methods involving the identification of unique radiolytic products derived from aromatic compounds, DNA and fatty acids. We also review the applications of spectroscopic methods such as thermoluminescence and electron spin resonance spectroscopy in this area. In particular, attention is focused on the recent application of high-field, high-resolution nuclear magnetic resonance (NMR) spectroscopy as a method for distinguishing between irradiated and non-irradiated foodstuffs. Where appropriate, attention is drawn to limitations or potential sources of error in the analytical methods employed.

1H NMR investigations of the molecular nature of low-molecular-mass calcium ions in biofluids

Abstract. High-resolution 1H NMR spectroscopy was employed to explore the complexation of Ca2+ by low-molecular-mass biomolecules in human saliva. The results acquired revealed that the organic acid anion (OAA) citrate acts as a powerful oxygen-donor chelator for salivary Ca2+, and accurate determination of its resonances frequencies and spin-system pattern could be successfully utilized to determine its degree of saturation with this metal ion. Computer modelling studies demonstrated that the OAA lactate is the only competing salivary Ca2+ complexant available. Moreover, the Ca2+-complexation status of salivary citrate is substantially modified by dentifrice-mediated elevations in its concentration. 1H NMR analysis was also applied to determinations of the Ca2+ saturation status of citrate in a variety of alternative biofluids and the biochemical significance of these results is discussed.

An optical hydroxyl radical sensor

A hydroxyl radical (.OH) fibre-optic sensor has been developed. An .OH radical-sensitive reagent phase (nitrophenol) was immobilized onto XAD-7 methacrylate beads. Subsequently the beads were attached to the distal end of a polymethylmethacrylate fibre optic. Nitrocatechol, generated from the attack of .OH radical on nitrophenol, exhibits a strong absorption band in the visible region of the electromagnetic spectrum (lambda max = 510 nm). Here, reflectance spectroscopy was employed to monitor the concomitant intensity decrease in the reflectance spectrum upon .OH radical attack. The sensor exhibited excellent stability and linearity of response to .OH generated by a Fenton reaction system (EDTA, Fe(II) and H2O2) with H2O2 over the concentration range of 3.6 x 10(-6)-8.0 x 10(-2) M.