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Tamoxifen and related compounds decrease membrane fluidity in ox‐brain phospholipid liposomes: their order of effectiveness is, 4‐hydroxytamoxifen > 17β‐oestradiol > tamoxifen > cis ‐tamoxifen > N ‐desmethyltamoxifen > cholesterol. A good positive correlation was demonstrated between the decrease in membrane fluidity by these compounds and their antioxidant ability as inhibitors of liposomal and microsomal lipid peroxidation (correlation coefficient, r = 0.99, P < 0.001, in both cases). The ability of tamoxifen to decrease membrane fluidity is suggested to be the mechanism of its antioxidant action and is discussed in relation to its anticancer and cardioprotective actions.
The elastase-inhibitory capacity of purified human alpha 1-antiproteinase is inactivated by low concentrations of the myeloperoxidase-derived oxidant hypochlorous acid, but much higher concentrations are required to inhibit the elastase-inhibitory capacity of serum samples. The protective effect of serum appears to be largely due to albumin. High concentrations of H2O2 also inactivate the elastase-inhibitory capacity of alpha 1-antiproteinase, by a mechanism not involving formation of hydroxyl radicals. Serum offers protection against H2O2 inactivation of alpha 1-antiproteinase. The relevance of these results to the tissue damage produced by activated phagocytes is discussed.
Correspondence| August 01 1988 The deoxyribose assay: an assay both for 'free' hydroxyl radical and for site-specific hydroxyl radical production J M C Gutteridge; J M C Gutteridge Search for other works by this author on: This Site PubMed Google Scholar B Halliwell B Halliwell Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1988) 253 (3): 932–933. https://doi.org/10.1042/bj2530932 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation J M C Gutteridge, B Halliwell; The deoxyribose assay: an assay both for 'free' hydroxyl radical and for site-specific hydroxyl radical production. Biochem J 1 August 1988; 253 (3): 932–933. doi: https://doi.org/10.1042/bj2530932 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1988 London: The Biochemical Society1988 Article PDF first page preview Close Modal You do not currently have access to this content.
Peroxynitrite is a cytotoxic species generated by the reaction between superoxide and nitric oxide. The ability of catechins and their gallate esters to decrease peroxynitrite-induced nitration of tyrosine and to limit surface charge alteration of low density lipoprotein (LDL) was investigated. All compounds tested were found to be potent peroxynitrite scavengers preventing the nitration of tyrosine. The ability of the catechin polyphenols at 10 μM to minimise tyrosine nitration induced by peroxynitrite (500 μM) was ECG (38.1 ± 3.6%) ≈ EGCG (32.1 ± 7.5%) ≈ gallic acid (32.1 ± 1.9%) > catechin (23.9 ± 5.4%) ≈ epicatechin (22.9 ± 3.3%) ≈ EGC (19.9 ± 2.0%). Trolox (10 μM) was used as the standard for comparative purposes and was found to be less effective than the polyphenols in inhibiting tyrosine nitration (13.6 ± 2.9%). The catechin polyphenols were also found to offer protection from peroxynitrite-induced modification of critical amino acids of apolipoprotein B-100 of LDL which contribute towards its surface charge.
Scavenging of the ABTS (2,2'-azinobis[3-ethylbenzothiazoline-6-sulphonate])-derived nitrogen-centred radical cation (ABTS*+) was used to compare the total antioxidant activities of several seasonings used in Asian cooking. The results were expressed as Trolox equivalent antioxidant capacity (TEAC). The TEAC activities of dark soy sauces were found to be exceptionally high. In evaluating the TEAC of commercial products, attention must be paid to the addition of preservatives by manufacturers to the seasonings tested. Sodium benzoate (a preservative added to several seasonings) did not react significantly with ABTS*+, but the sulphite content of certain white wines may have led to an over-estimation of their TEAC.
Hydrogen peroxide (H2O2) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H2O2 is poorly reactive in the absence of transition metal ions. Exposure of certain human tissues to H2O2 may be greater than is commonly supposed; levels of H2O2 in the human body may be controlled not only by catabolism but also by excretion, and H2O2 could play a role in the regulation of renal function and as an antibacterial agent in the urine. Cell culture is a widely used method for the investigation of “physiological” processes such as signal transduction and regulation of gene expression, but chemical reactions involving cell culture media are rarely considered. Addition of reducing agents to commonly used cell‐culture media can lead to generation of substantial amounts of H2O2. Some or all of the reported effects of ascorbic acid and polyphenolic compounds (e.g., quercetin, catechin, epigallocatechin, epigallocatechin gallate) on cells in culture may be due to H2O2 generation by interaction of these compounds with cell culture media.
1. In the presence of dihydroxyfumarate, horseradish peroxidase catalyses the conversion of p-coumaric acid into caffeic acid at pH 6. This hydroxylation is completely inhibited by superoxide dismutase. 2. Dihydroxyfumarate cannot be replaced by ascorbate H2O2, NADH, cysteine or sulphite. Peroxidase can be replaced by high (10 mM) concentrations of FeSO4, but this reaction is almost unaffected by superoxide dismutase. 3. Hydroxylation by the peroxidase/dihydroxyfumarate system is completely inhibited by low concentrations of Mn2+ or Cu2+. It is proposed that this is due to the ability of these metal ions to react with the superoxide radical O2--. 4. Hydroxylation is partially inhibited by mannitol, Tris or ethanol and completely inhibited by formate. This seems to be due to the ability of these reagents to react with the hydroxyl radical -OH. 5. It is concluded that O2-- is generated during the oxidation of dihydroxyfumarate by peroxidase and reacts with H2O2 to produce hydroxyl radicals, which then convert p-coumaric acid into caffeic acid.
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The antioxidant and antiviral actions of the herbal extracts Rovital and Carciverin-V (C1983) were assessed. Solutions of Rovital and C1983 are powerful scavengers of hydroxyl radicals. Rovital did not inhibit DNA damage by bleomycin or copper-phenanthroline systems, whereas C1983 inhibited moderately. C1983 had significant inhibitory effects on the peroxidation of phospholipid liposomes whereas Rovital did not. However, Rovital and C1983 also interfered with the ability of α1-antiproteinase to inhibit elastase. The extracts exhibited anti-HIV activity in C8166 cells at very low concentrations but were also cytotoxic.
When cells are exposed to oxidative stress, DNA damage frequently occurs. The molecular mechanisms causing this damage may include activation of nucleases and direct reaction of hydroxyl radicals with the DNA. Several oxygen‐derived species can attack DNA, producing distinctive patterns of chemical modification. Observation of these patterns and measurement of some of the products formed has been used to determine the role of different oxygen‐derived species in DNA cleavage reactions, to assess the extent of oxidative damage to DNA in vivo and to investigate the mechanism of DNA damage by ionizing radiation and chemical carcinogens.
There is considerable current interest in the possible beneficial health effects of quercetin, catechins, epigallocatechins, epigallocatechin gallates, and related phenolic compounds found in teas, wines, and other plant products. As a result, many laboratories are studying the effects of these compounds on cells in culture. The present paper shows that addition of these compounds to commonly used cell culture media leads to generation of substantial amounts of hydrogen peroxide (H2O2). Dulbecco's modified Eagle medium gives the highest H2O2 level for all the compounds tested, with levels reaching >400 μM within 2 h for addition of 1 mM concentrations of gallic acid, epigallocatechin gallate, and epigallocatechin. Catechin and quercetin produced lower, but still significant, levels of H2O2. McCoy's 5A and RPMI 1640 media also promoted H2O2 production from the above phenolic compounds. This rapid generation of H2O2 could account for some or all of the reported effects of phenolic compounds on cells in culture.
Thiourea and dimethylthiourea are powerful scavengers of hydroxyl radicals (.OH), and dimethylthiourea has been used to test the involvement of .OH in several animal models of human disease. It is shown that both thiourea and dimethylthiourea are scavengers of HOCl, a powerful oxidant produced by neutrophil myeloperoxidase. Hence the ability of dimethylthiourea to protect against neutrophil-mediated tissue damage cannot be used as evidence for a role of .OH in causing such damage. Dimethyl sulphoxide also reacts with HOCl, but at a rate that is probably too low to be biologically significant at dimethyl sulphoxide concentrations up to 10 mM. Neither mannitol nor desferrioxamine, at the concentrations normally used in radical-generating systems, appears to react with HOCl.
