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.
"The Antioxidant Vitamins C and E: Packer L, Traber MG, Kramer K and Frei B. (Eds) AOCS Press, Champaign, Illinois, 2002." Free Radical Research, 37(10), p. 1146
Free radicals and other reactive species are constantly generated in vivo and cause oxidative damage to DNA at a rate that is probably a significant contributor to the age-related development of cancer. Agents that decrease oxidative DNA damage should thus decrease the risk of cancer development. That is, oxidative DNA damage is a “biomarker” for identifying persons at risk (for dietary or genetic reasons, or both) of developing cancer and for suggesting how the diets of these persons could be modified to decrease that risk. This biomarker concept presupposes that we can measure oxidative damage accurately in DNA from relevant tissues. Little information is available on whether oxidative DNA damage in blood cells mirrors such damage in tissues at risk of cancer development. Measurement of 8-hydroxylated guanine (eg, as 8-hydroxy-2′-deoxyguanosine; 8OHdG) is the commonest method of assessing DNA damage, but there is no consensus on what the true levels are in human DNA. If the lowest levels reported are correct, 8OHdG may be only a minor product of oxidative DNA damage. Indeed, 8OHdG may be difficult to measure because of the ease with which it is formed artifactually during isolation, hydrolysis, and analysis of DNA. Mass spectrometry can accurately measure a wide spectrum of DNA base damage products, but the development of liquid chromatography–mass spectrometry techniques and improved DNA hydrolysis procedures is urgently required. The available evidence suggests that in Western populations, intake of certain fruit and vegetables can decrease oxidative DNA damage, whereas ascorbate, vitamin E, and β-carotene cannot.
The most stable oxidation number of iron is ferric. Superoxide attack enzymes containing an iron-sulfur cluster, such as bacterial dihydroxyacid dehydratase, aconitase, or 6-phosphogluconate dehydrogenase. The search for cheap orally active alternatives to desferriox-amine has led to the development of a range of hydroxypyridone iron chelators. Hydroxypyridones can apparently remove iron ions from transferrin and lactoferrin, which are "safe" forms of iron unable to catalyze free-radical reactions. The importance of iron ions in mediating oxidative damage naturally leads to the question as to what forms of iron might be available to catalyze radical reactions in vivo. Bleomycin-detectable iron has also been measured in human sweat, in some cerebrospinal fluid samples, in synovial fluid from human knee joints, and in extracts of several bacterial strains. The ability of lactoferrin to resist damage by oxidants generated at sites of inflammation is consistent with such a role.
The term antioxidant is widely used but rarely defined. One suggested definition is that an antioxidant is 'a substance that, when present at low concentrations compared with those of an oxidizable substrate, significantly delays or prevents oxidation of that substrate'. Many substances have been suggested to act as antioxidants in vivo, but few have been proved to do so. This chapter addresses the criteria necessary to evaluate a proposed antioxidant activity. Simple methods for assessing the possibility of physiologically feasible scavenging of important biological oxygen-derived species (superoxide, hydrogen peroxide, hydroxyl radical, hypochlorous acid, haem-associated ferryl species, radicals derived from activated phagocytes and peroxyl radicals, both lipid-soluble and water-soluble) are presented. Methods that may be used to gain evidence that a compound actually does function as an antioxidant in vivo are discussed.
Fungal systems have harnessed the power of reactive oxygen species to achieve breakdown of one of the world's toughest substances, wood. To attain this goal, powerful oxidizing agents must be used. However, such agents present a risk to the fungal cells generating them. If they are highly reactive, there is a further risk that they will be dissipated in non-productive reactions with environmental biomolecules unless they are selectively delivered to their sites of action. Let us examine the basic chemistry of some reactive species to see what might be possible. Oxidations by oxygen Oxygen itself is a biradical, containing two unpaired electrons. The parallel spin of these two electrons makes it difficult for oxygen to react directly with nonradicals. As a result, direct oxidation of most biomolecules with O2 is slow. Wood is the perfect example; it resists direct oxidation by O2 for centuries. However oxygen does react fast with
The carbonyl assay has been developed as a general assay of oxidative protein damage to assess steady-state protein damage in animal tissues and body fluids. The assay is based on the fact that several ROS can attack amino acid residues in proteins (particularly histidine, arginine, lysine, and proline) to produce carbonyl functions that can react with 2,4-dinitrophenylhydrazine (DNPH) to generate chromophoric dinitrophenylhydrazones. This reaction can, therefore, be used to estimate the carbonyl content of proteins in human tissues and body fluids. Western blotting assays based on the use of anti-dinitrophenol antibodies have also been developed to identify oxidatively damaged proteins in tissues and body fluids after their extraction and derivatization with DNPH. The carbonyl assay has become widely used and many laboratories have developed individual protocols for it. Sometimes, the assay procedures used are not precisely specified, and when they are, they may differ from those originally proposed by the group of Stadtman et al. This point is important, because there is considerable variation in the baseline levels of protein carbonyls in certain tissues, depending on how the assay is performed.
