Oxalic acid

About: Oxalic acid is a research topic. Over the lifetime, 11584 publications have been published within this topic receiving 173263 citations. The topic is also known as: ethanedioic acid & H2ox.

Manganese Peroxidase-Dependent Oxidation of Glyoxylic and Oxalic Acids Synthesized by Ceriporiopsis subvermispora Produces Extracellular Hydrogen Peroxide.

Abstract: The ligninolytic system of the basidiomycete Ceriporiopsis subvermispora is composed of manganese peroxidase (MnP) and laccase. In this work, the source of extracellular hydrogen peroxide required for MnP activity was investigated. Our attention was focused on the possibility that hydrogen peroxide might be generated by MnP itself through the oxidation of organic acids secreted by the fungus. Both oxalate and glyoxylate were found in the extracellular fluid of C. subvermispora cultures grown in chemically defined media, where MnP is also secreted. The in vivo oxidation of oxalate was measured; 14CO2 evolution was monitored after addition of exogenous [14C]oxalate to cultures at constant specific activity. In standard cultures, evolution of CO2 from oxalate was maximal at day 6, although the MnP titers were highest at day 12, the oxalate concentration was maximal (2.5 mM) at day 10, and the glyoxylate concentration was maximal (0.24 mM) at day 5. However, in cultures containing low nitrogen levels, in which the pH is more stable, a better correlation between MnP titers and mineralization of oxalate was observed. Both MnP activity and oxidation of [14C]oxalate were negligible in cultures lacking Mn(II). In vitro assays confirmed that Mn(II)-dependent oxidation of [14C]oxalate by MnP occurs and that this reaction is stimulated by glyoxylate at the concentrations found in cultures. In addition, both organic acids supported phenol red oxidation by MnP without added hydrogen peroxide, and glyoxylate was more reactive than oxalate in this reaction. Based on these results, a model is proposed for the extracellular production of hydrogen peroxide by C. subvermispora.

Relationships between calcium and oxalic acid intake in the diet and their excretion in the urine of normal and renal-stone-forming subjects.

Abstract: 1. The short-term effects of different intakes of calcium and oxalic acid on the urinary excretion of these substances was studied in eight normal men and eight men with a history of calcium-containing renal stones. 2. The effect of dietary oxalate on urine oxalate depended partly upon the calcium intake. Thus, on a normal calcium intake an increase in oxalate intake caused an increase in oxalate excretion that corresponded to 3·6% of the additional dietary oxalate; on a low calcium diet, however, the increase corresponded to 8·1%. 3. A decrease in daily calcium intake from 1000 to 250 mg caused a fall in calcium excretion averaging 150 mg/day in the patients and 60 mg/day in the controls but this was accompanied by average rises of 10 and 7 mg/day respectively in oxalate excretion, with the result that the calcium oxalate activity products remained almost unchanged. 4. A decrease in oxalate as well as calcium intake resulted in a fall in calcium excretion that was not accompanied by a rise in oxalate excretion, and there was a statistically significant fall in the calcium oxalate activity product in both the patients and normal subjects.

Synthesis of some Compounds Possessing Vitamin A Activity

Abstract: WE have prepared â vitamin A acidâ (VII) from I-ionone as indicated in the following scheme: