Complexes of iron with phenolic compounds from soybean nodules and other legume tissues: prooxidant and antioxidant properties.
The low-molecular-mass fraction of the soybean nodule cytosol contains Fe capable of catalyzing free radical production through Fenton chemistry. A large portion of the pool of catalytic Fe, measured as bleomycin-detectable Fe, was characterized as complexes of Fe with phenolic compounds of three classes: phenolic acids, cinnamic acids, and flavonoids. Many of these compounds, along with other phenolics present in legume tissues, were used for a systematic structure-activity relationship study. All phenolics tested were able to chelate Fe, as judged from their inhibitory effect on site-specific deoxyribose degradation (minus EDTA assay). However, only those having catechol, pyrogallol, or 3-hydroxy-4-carbonyl groupings were potent chelators and reductants of Fe3+ at pH 5.5. The same phenolics promoted oxidative damage to DNA (bleomycin assay) and to deoxyribose (plus EDTA assay), but inhibited linolenic acid peroxidation by chelating and reducing Fe3+ and by neutralizing lipid radicals. Also, phenolics having a pyrogallol nucleus attenuated the free radical-mediated inactivation of glutamine synthetase, which was used as a model system, by chelating Fe2+. It is reasoned that under the microaerobic (10-20 nM O2) and acidic (pH 5.5-6.4) conditions prevailing in nodules, phenolics are likely to act primarily as antioxidants, decreasing oxidative damage to biomolecules.
Moran
J F
JF
Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, CSIC, Zaragoza, Spain.
Klucas
R V
RV
Grayer
R J
RJ
Abian
J
J
Becana
M
M
D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D004249:DNA Damage; D003855:Deoxyribose / Q000378:metabolism; D007887:Fabaceae / Q000378:metabolism; D005609:Free Radicals / Q000378:metabolism; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D015227:Lipid Peroxidation; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010636:Phenols / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism; D010946:Plants, Medicinal; D013025:Glycine max / Q000378:metabolism*
D000975:Antioxidants; D005609:Free Radicals; D016877:Oxidants; D010636:Phenols; D010940:Plant Proteins; D003855:Deoxyribose; D007501:Iron