High Concentration Of Oxalic Acid Research Articles

Dietary calcium and health

Dietary calcium and health

Enhancing resistance to Sclerotinia minor in peanut by expressing a barley oxalate oxidase gene.

Sclerotinia minor Jagger is the causal agent of Sclerotinia blight, a highly destructive disease of peanut (Arachis hypogaea). Based on evidence that oxalic acid is involved in the pathogenicity of many Sclerotinia species, our objectives were to recover transgenic peanut plants expressing an oxalic acid-degrading oxalate oxidase and to evaluate them for increased resistance to S. minor. Transformed plants were regenerated from embryogenic cultures of three Virginia peanut cultivars (Wilson, Perry, and NC-7). A colorimetric enzyme assay was used to screen for oxalate oxidase activity in leaf tissue. Candidate plants with a range of expression levels were chosen for further analysis. Integration of the transgene was confirmed by Southern-blot analysis, and gene expression was demonstrated in transformants by northern-blot analysis. A sensitive fluorescent enzyme assay was used to quantify expression levels for comparison to the colorimetric protocol. A detached leaflet assay tested whether transgene expression could limit lesion size resulting from direct application of oxalic acid. Lesion size was significantly reduced in transgenic plants compared to nontransformed controls (65%-89% reduction at high oxalic acid concentrations). A second bioassay examined lesion size after inoculation of leaflets with S. minor mycelia. Lesion size was reduced by 75% to 97% in transformed plants, providing evidence that oxalate oxidase can confer enhanced resistance to Sclerotinia blight in peanut.

Oxalic acid concentrations in Purslane ( Portulaca oleraceae L.) is altered by the stage of harvest and the nitrate to ammonium ratios in hydroponics

Oxalic acid (OA) occurs naturally in a large number of plant species. When present in the human diet, OA may combine with essential minerals such as calcium and iron, to form insoluble salts known as oxalates and hinder their bio-availability. Purslane ( Portulaca oleracea, Portulacaceae) is an excellent source of omega-3 fatty acids and anti-oxidant vitamins. However, its consumption as a green vegetable is limited by high concentrations of OA. In previous studies we reported the influence of nitrate to ammonium ratios in hydroponics on the leaf omega-3 fatty acid concentrations. In this study we determined the NO 3 −-N:NH 4 +-N ratio in hydroponics and the stage of harvest that would minimize the oxalic acid concentrations in purslane leaves. Fully expanded leaves were harvested at 8-true leaf and at 16-true leaf stages from purslane plants grown in hydroponic systems containing nitrogen (200 μg ml −1) as nitrate (NO 3 −) to ammonium (NH 4 +) ratios (1:0, 0.75:0.25, 0.5:0.5 and 0.25:0.75), and analyzed for OA concentrations. Results indicate that at both stages of harvest the OA concentrations were ≈40–50% lower in the leaves grown in solutions containing ammonium compared to the leaves grown with no ammonium. Leaves harvested at 16-true leaf stage had ≈36–45% lower OA concentrations compared to the leaves harvested at 8-true leaf stage. The dry weight (DW), fresh weight (FW) and leaf area (LA) were greater at 16-true leaf stage than at 8-true leaf stage, but were not influenced by the NO 3 −:NH 4 + ratios in hydroponics.

Protein extraction from Atriplex lampa leaves: potential use as forage for animals used for human diets.

The purpose of this study was to evaluate the effect of pH on the extraction of protein nitrogen from Atriplex lampa leaves (Moquin) Dietrich. The chemical characterization of the dry matter indicated the following (g/100 g): protein, 26.93; ash, 21.80; ether extract, 4.65; dry matter, 37.30; sodium, 6.05; and calcium, 0.41. Non-critical values were obtained for saponins and nitrates. The high concentration of oxalic acid (8.52 g/100 g), together with elevated salt content account for the low palatability of the studied species. In order to determine the parameters needed to improve the extraction in protein nitrogen from leaves, fresh material was macerated with 2% sodium metasulfite, followed by pulping with a hand-driven grinder. Extractions were performed at different pH values (2-12) adjusting the value with 5N HCL or NaOH, with agitation followed by centrifugation and pressing. Supernatants were collected and kept. The last extraction was performed with Tween 20 in order to obtain maximum nitrogen recovery from the residue cake. Highest extraction (41.23%) was obtained at pH 10 with a 1:5 ratio (leaf: deionized water, w/v). It is proposed that this regional natural resource may be used to elaborate a protein concentrate, which can be made more palatable by decreasing potassium and sodium salt content with the use of membrane technology.

Oxalic acid production by Aspergillus niger

Aspergillus niger is able to produce a quite high concentration of oxalic acid using sucrose as carbon and energy source. Operating at pH higher than 6 and an enriched N and P medium is necessary in order to conduct the fermentation towards oxalic acid production. A pH shift technique, operating at acid pH in the first two days and then setting pH to 6, allowed the productivity to slightly increase in shaking flasks cultures up to 3.0 kg/m3 · d, with a final oxalic acid concentration of 29 kg/m3. When operating at more controlled conditions, in a stirred tank, both productivity and oxalic acid concentration were improved (4.1 kg/m3 · d and 33.8 kg/m3, respectively). However the main drawback of this fermentation is the low yield attained (about 0.3 kg oxalic acid/kg sucrose) because most of glucose, resulting from the hydrolysis of sucrose by the extracellular enzymes secreted at the beginning of the fermentation, is very quickly oxidised to gluconic acid, a process which is favoured at a pH close to 6. Milk whey was proved to be a very good substrate as it allows oxalic acid to be produced with a similar productivity (2.5 kg/m3 · d in shaking flasks) giving excellent yields of almost 0.6 kg oxalic acid/kg lactose.

Oxalic acid production by Aspergillus niger

Aspergillus niger is able to produce a quite high concentration of oxalic acid using sucrose as carbon and energy source. Operating at pH higher than 6 and an enriched N and P medium is necessary in order to conduct the fermentation towards oxalic acid production. A pH shift technique, operating at acid pH in the first two days and then setting pH to 6, allowed the productivity to slightly increase in shaking flasks cultures up to 3.0 kg/m 3 . d, with a final oxalic acid concentration of 29 kg/m 3 . When operating at more controlled conditions, in a stirred tank, both productivity and oxalic acid concentration were improved (4.1 kg/m 3 . d and 33.8 kg/m 3 , respectively). However the main drawback of this fermentation is the low yield attained (about 0.3 kg oxalic acid/kg sucrose) because most of glucose, resulting from the hydrolysis of sucrose by the extracellular enzymes secreted at the beginning of the fermentation, is very quickly oxidised to gluconic acid, a process which is favoured at a pH close to 6. Milk whey was proved to be a very good substrate as it allows oxalic acid to be produced with a similar productivity (2.5 kg/m 3 . d in shaking flasks) giving excellent yields of almost 0.6 kg oxalic acid/ kg lactose.

Low molecular weight organic acids released from roots of durum wheat and flax into sterile nutrient solutions

Knowledge of the composition and quantity of organic substances released from roots of different plant species is necessary for understanding the chemical and biological processes in the rhizosphere. The present study was undertaken to quantify low molecular weight organic acids (LMWOAs) released from roots of five cultivars/lines of durum wheat (Triticum turgidum var. durum L.): Kyle, Sceptre, DT618, DT627, and DT637 and four cultivars/ lines of flax (Linum usitatissiumum L.): Somme, Flanders, AC Emerson, and YSED 2. Plants were grown in sterile nutrient solution cultures and amounts of organic acids exuded by roots were analyzed by gas chromatography. The LMWOAs varied significantly among both durum wheat and flax cultivars and oxalic, malonic, fumaric, succinic, acetic, malic, citric and tartaric acids were detected in root exudates of both species. Generally, oxalic and acetic acids were predominant in durum wheat exudates and oxalic, acetic and malic acids were predominant in flax root exudates. High oxalic acid concentrations occurred in root exudates of durum wheat cultivars DT627 and DT637, and flax cultivar YSED 2. Compared with the other durum wheat cultivars, Kyle released the lowest total amount of LMWOAs, whereas among the flax cultivars, YSED 2 had the highest total amount of acids secreted from roots. The data showed that the release of LMWOAs from roots was cultivar dependent. The results provide valuable background information for studying the role of root exudates in soil‐plant relationships.

Source and reaction pathways of dicarboxylic acids, ketoacids and dicarbonyls in arctic aerosols: One year of observations

Normal saturated (C 2C 11) and unsaturated (C 4C 5, C 8) dicarboxylic acids were measured in arctic aerosol samples collected weekly at Alert, Canada in 1987–1988. In all seasons, oxalic (C 2) acid was usually the dominant diacid species (1.8−70 ng m −3, av. 14 ± 12 ng m −3) followed by malonic (C 3; 0.05−19 ng m −3, av. 2.5 ± 3.3 ng m −3) and succinic (C 4; 0.51−18 ng m −3, av. 3.8 ± 3.5 ng m −3) acids. The total concentrations of dicarboxylic acids showed a seasonal variation (4.3−97 ng m −3, av. 25 ± 20 ng m −3),with two maxima in September to October and in March to April. The autumn peak is characterized by high concentrations of oxalic acid and azelaic (C 9) acids, which were probably caused by enhanced contributions from anthropogenic and biogenic sources, respectively, followed by photochemical reactions. This is consistent with higher concentrations of n-alkanes from terrestrial plant waxes and of soil-derived aluminum in the autumn aerosol samples. On the other hand, during “Arctic Sunrise” in March to April, oxalic, malonic and succinic acids as well as some other (C 5C 6) diacids were 5 to 20 times more abundant than in the preceding dark winter months, suggesting that diacids are produced in situ by secondary photochemical oxidation of organic pollutants carried to the Arctic. ω-Oxocarboxylic acids (C 2C 5, C 9), pyruvic acid and α-dicarbonyls (methylglyoxal and glyoxal) were also detected in the arctic aerosols. Their concentration also showed spring maxima; however, they were observed a few weeks earlier than the spring peak of diacids. The ω-oxoacids are likely intermediates to the production of α,ω-dicarboxylic acids at the polar sunrise.

Calcium bioavailability and its relation to osteoporosis.

The balance of data suggests that calcium intake has a positive influence on bone mass in premenopausal women and has a preventive effect on the rate of bone loss in postmenopausal women. Even small advantages in bone mass provide great reductions in fracture rates. However, the majority of studies have tested the relationship of calcium intake and bone mass using calcium supplements. Few intervention studies have manipulated calcium intake through foods. Calcium is only useful to the skeleton once it is absorbed. Therefore, the bioavailability of dietary calcium becomes important in the prevention and treatment of osteoporosis. Isotopic tracer techniques have only recently been employed in the labeling of foods with calcium isotopes for evaluation of calcium absorption. Milk calcium is usually the referent food which is typically absorbed at 20-40% depending on the calcium status of the subject. The absorptive efficiency of most vegetable sources is as good or better than for dairy foods, unless they have high concentrations of oxalic acid (spinach, for example) or phytic acid (wheat bran cereal, for example). Few vegetable sources are concentrated sources of calcium. Therefore, it would be difficult to obtain adequate intakes of calcium to protect against osteoporosis without liberal use of dairy products in the diet. Alternately, calcium supplements provide concentrated amounts of absorbable calcium, but they do not provide other nutrients necessary for skeletal growth and maintenance.

Ligand Exchange and Redox Reactions of Chromium(V): Isolation of the Chromium(V) Oxalato Complexes From the Ligand Exchange Reaction of Bis[2-ethyl-2-hydroxybutanoato(2-)]oxochromate(V) With Oxalate in 50% Aqueous Acetic Acid

The moderately stable chromium(v) complex, trans-bis[2-ethyl-2-hydroxybutanoato(2-)] oxo -chromate(v), [Cr( ehba )2O]- (1), has been assessed for its suitability as a synthetic intermediate for the preparation of other chromium(v) complexes. This complex undergoes a ligand exchange reaction with excess oxalic acid to form an equilibrium mixture of chromium(v) complexes which have been assigned the structures [Cr( ehba )2O]-, [Cr( ehba )(ox)O]- (2), [Cr(ox)2O]- (3) and cis -[Cr(ox)2(OH2)O]- (4). The products of the ligand exchange reaction were characterized by a combination of u.v ./visible spectroscopy, e.p.r . spectroscopy and electrochemistry. The equilibrium mixture of chromium(v) complexes decays to form chromium(III) products by a redox reaction which is much slower than the initial ligand exchange reaction. The difference in the rates of ligand exchange and subsequent reduction allows the extraction of the chromium(v) ligand exchange products into dichloromethane. n.m.r. spectroscopy and electrochemical techniques were used to identify these products. Under appropriate conditions (high oxalic acid concentrations) the major species extracted are the bis [ oxalato (2-)] oxochromate (v) complexes which have been isolated as oily solids in relatively pure form (≥90% pure) for the first time. n.m.r. spectroscopic evidence indicates that the isolated solid was a mixture of (3) and (4) which explains the difficulty encountered in crystallizing the solid. These ligand exchange reactions may be of general utility in the synthesis of chromium(v) complexes.

Effect of Succinimide on Hyperoxaluria in the Rat

In the female rat intoxicated with ethylene glycol the oxaluria increases with the degree of intoxication. The increase is less in the animals treated with succinimide. The comparative study of the results of the dosages made with gas-liquid-chromatography and by various colorimetric methods show that this later gives varying results and underestimates high concentrations of oxalic acid. The result is that any study based on results of dosages of urinary oxalic acid made by colorimetry must be taken with some reserve, and this on whether the oxalic lithiasis is experimentally induced or human, or whether its evolution is spontaneous or influenced by a therapeutic.

Spectrophotometric determination of formaldehyde, glycollic and glyoxalic acids in the presence of glyoxal and some carboxylic acids

A spectrophotometric procedure is described for determining glycollic acid, glyoxalic acid and formaldehyde in the presence of high concentrations of oxalic acid and ammonium oxalate, and in the presence of glyoxal, formic acid, tartaric acid, and dihydroxytartaric acid. Three known spectrophotometric methods required modification. The experimental error under the specified conditions does not exceed ±5%.