ascorbic-acid and Favism

Favism is an acute hemolysis occurring in glucose-6-phosphate dehydrogenase (G6PD)-deficient (Mediterranean variant) individuals after intake of fava beans. Divicine (D), 2,6-diamino-4,5-dihydroxypyrimidine, is present in high amounts in the beans, and is suspected to play a role in hemolysis. Its mechanism of action was studied in a cell-free system and in G6PD (Mediterranean variant)-deficient red cells (RBC). Upon hydrolysis of the inactive beta-glucoside vicine, reduced divicine is formed. Oxygen acts as a one- or two-electron acceptor; superoxide anion and hydrogen peroxide are formed, respectively, together with the semiquinoid free-radical form of D. This free radical gives an electron spin resonance (ESR) signal, which is similar to that of the alloxan free radical. Added reduced glutathione (GSH) is rapidly oxidized with a stoichiometry of one to one, and the ESR signal is abolished. Additional GSH is oxidized by hydrogen peroxide and by a slow redox cycle which continuously regenerates oxidized D. The fast-direct and the slow-indirect oxidation result in nonstoichiometric oxidation of GSH. D added to G6PD-deficient RBC rapidly oxidizes GSH with an end point kinetics and a stoichiometry of one to one. Hydrogen peroxide and superoxide anion are scavenged in the RBC and no redox cycling is taking place. No GSH is regenerated even after long incubation periods. After the primary event, i.e., oxidation of GSH and--SH groups, a number of metabolic, rheologic, and membrane modifications, together with increased erythrophagocytosis take place in G6PD-deficient, D-treated RBC only.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Ascorbic Acid; Cell-Free System; Cytochrome c Group; Erythrocytes; Favism; Glucosephosphate Dehydrogenase Deficiency; Glutathione; Hemolysis; Humans; Hydrogen Peroxide; In Vitro Techniques; Kinetics; Male; Oxidation-Reduction; Pyrimidinones; Superoxides

Enzymatic activity of purified or membrane-bound acetylcholine esterase was lost when incubated aerobically in the presence of both favism-inducing agent (isouramil or divicine) and copper ions. The requirement for oxygen could be substituted by hydrogen peroxide. Chelating agents provided total protection to the proteins. The suggested mechanism of enzymatic inactivation is analogous to that suggested earlier for the effects of superoxide and ascorbate, and involves the site-specific formation of hydroxyl radicals in the metal-mediated Haber-Weiss reaction. These findings may be relevant to the understanding of the pathogenesis of favism.

Topics: Ascorbic Acid; Barbiturates; Cholinesterase Inhibitors; Copper; Electron Spin Resonance Spectroscopy; Favism; Humans; In Vitro Techniques; Oxidation-Reduction; Pyrimidinones

Red blood cells of favism patients with acute hemolytic crisis have markedly more superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) and less glutathione peroxidase (glutathione:hydrogenperoxide oxidoreductase, EC 1.11.1.9) than either normal controls, glucose-6-phosphate dehydrogenase-deficient subjects or favism patients outside hemolytic crisis. This altered value of the two enzyme activities is not due to increased reticulocyte content of blood. The electrophoretic triplet pattern of superoxide dismutase is also changed, with significant increase of the most positively charged band. Similar modifications of the two enzyme activities are observed after treatment of normal red blood cells with high concentrations of divicine and ascorbate, which are redox compounds that are contained in fava seeds. This treatment produces no hemolysis, but leads to hemolysis if the treated cells are resuspended in the homologous plasma. These results suggest a possible role of active oxygen species in the development of favism.

Topics: Ascorbic Acid; Electrophoresis, Polyacrylamide Gel; Erythrocyte Aging; Erythrocytes; Favism; Glutathione Peroxidase; Hemolysis; Humans; Oxidation-Reduction; Pyrimidinones; Reticulocytes; Superoxide Dismutase

Fava beans contain high amounts (up to 6.7 g/100 g dry weight) vicine and convicine. Their active aglycones divicine and isouramil have equivalent metabolic effects. They rapidly oxidize GSH to GSSG in normal and G6PD-deficient red cells. No regeneration of GSH occurs in deficient cells. The stoichiometry of the divicine oxidation of GSH is 1:1. Ascorbic acid is quickly oxidized by isouramil in both normal and deficient cells but regenerates only in normal cells. Isouramil oxidizes NADH at a much lesser extent than NADPH. Glycolysis is activated at the glyceraldehyde 3-phosphate dehydrogenase step. Divicine strongly stimulates hexone monophosphate shunt only in normal red cells. Divicine alone or associated with ascorbic acid has almost no effect in deficient red cells. Malonyl dialdehyde production is slight and virtually the same in normal and deficient cells treated with 5 mM isouramil. Large polypeptide aggregates are formed after 12 and 24 hours incubation with 1 mM divicine in deficient cells only. Divicine (0.25 mM) markedly decreases the filterability of deficient cells. The results are consistent with a causal role of divicine/isouramil in the genesis of the hemolytic crisis occurring in G6PD-deficient subjects after fava bean ingestion.

Topics: Ascorbic Acid; Barbiturates; Erythrocytes; Favism; Glucosephosphate Dehydrogenase Deficiency; Glucosides; Glutathione; Humans; Kinetics; Pyrimidinones; Reference Values; Species Specificity; Toxins, Biological; Uracil; Uridine

Covicine + vicine, L-DOPA-glucoside + L-DOPA and ascorbic acid were determined in different lines of Vicia faba beans throughout the biological cycle of the plant. As the seed matures the levels of convicine + vicine as well as of ascorbic acid decrease with seed maturation in all the lines examined. L-DOPA, which is lacking in cotyledons but present in the tegument, also decrease and is nearly undectable in some lines with white flowers.

Topics: Ascorbic Acid; Fabaceae; Favism; Glucosides; Hemolysin Proteins; Levodopa; Plants, Medicinal; Pyrimidinones; Seeds; Uracil; Uridine

Topics: Adult; Ascorbic Acid; Edema; Favism; Female; Fetal Diseases; Glucosephosphate Dehydrogenase Deficiency; Humans; Infant, Newborn; Male; Pregnancy; Pregnancy Complications, Hematologic

Topics: Aminosalicylic Acid; Aminosalicylic Acids; Anemia; Anemia, Hemolytic; Ascorbic Acid; Drug Therapy; Favism; Glucosephosphate Dehydrogenase Deficiency; Glucosephosphates; Metabolism; Pharmacology; Toxicology; Tuberculosis; Tuberculosis, Cutaneous