Uric acid isolation

Modified procedure (ASC kit) Ascorbic acid is isolated from plasma proteins and uric acid in a single-step liquid gel chromatography procedure and its amount... 

Isoguanine (94), which is found in Prioneris wings along with hypoxanthine (92), xanthine (91), and uric acid (95), shows antineoplastic activities (Table VI) (57). Isolation of urocanic acid (137) from this wing material represents the first detection of this histidine derivative in an arthropod (Table VIII). A nonpteridine pigment, xanthommatin (58) (cf. Section II,B,l,b), is found in the larval body of Pieris brassicae (Table V). 

LDL becomes oxidized in vivo. There is evidence that LDL is protected against oxidation in plasma by water-soluble antioxidative substances, such as ascorbic acid, uric acid, or bilirubin. Thus, it is likely that the majority of oxidative modification of LDL occurs in the artery wall, where LDL is largely isolated from the plasmatic antioxidants. Recent evidence suggests that metal ions (copper or iron) and the enzymes myeloperoxidase and lipoxygenase play major parts in the modification of LDL [161]. 

The issues of whether hyperuricemia is an independent risk factor for cardiovascular disease and the clinical relevance of the rise in serum uric acid caused by diuretic treatment are controversial (SED-14, 660 351). In the Systolic Hypertension in the Elderly Program (SHEP), diuretic-based treatment in 4327 men and women, aged 60 years or more, with isolated systolic hypertension was associated with significant reduction in cardiovascular events (SED-14, 657). Serum uric acid independently... 

Xanthine oxidase catalyzes the oxidation of hypox-anthine and xanthine to uric acid. Xanthine oxidase is a complex metalloflavoprotein containing one molybdenum, one FAD and two iron-sulfur centers of the ferredoxine type in each of its two independent subunits. Usually, the enzyme is isolated from cow s milk. The enzyme is inhibited by allopurinol and related compounds. The production of uric acid from the substrate (xanthine) can be determined by measuring the change in optical density in the UV range. 

A very small number of children have been reported who are unable to synthesize molybdopterin they show severe neurological abnormalities shordy after birth and fail to survive more than a few days. As expected from the metabolic roles of molybdopterin, they have low blood concentrations of uric acid and sulfate, and abnormally high levels of xanthine and sulfite. The neurological damage is probably caused by sulfite, because similar abnormalities are seen in children with isolated sulfite oxidase deficiency (Reiss, 2000). 

The system was first named by Fischer 0899CB435) but the correct ring structure was proposed much earlier <1875LA( 175)243) in a formula for uric acid. In the general literature purine nomenclature has been to a large extent affected by the abundance of trivial names for compounds which were isolated before their structures were known and by variation in description of tautomeric forms. 

Alkylation of the triethylsilylated uric acid (120) with methyl iodide is unusual in produdng 1-methyluric acid but at 150 °C with dimethyl sulfate the major products isolated were... 

Purine derivatives are considered to be prebiotic molecules. Purine as well as adenine (HCN) can be formed from hydrogen cyanide in the presence of ammonia in a prebiotic atmosphere. Similar reaction in the presence of water can lead to other purines. Purine chemistry goes back to the roots of organic chemistry. Uric acid was the first purine isolated from bladder stones by Scheelc in 1776. The correct empirical formula of uric acid was established much later by Liebig and Mitscherlich. The correct structure was suggested by L. Medicus and was shown to be correct by the syntheses ofHorbaezewski. Behrend and Roosen, and unambiguously by E. Fischer. The development of purine chemistry by E. Fischer is a milestone in heterocyclic chemistry. 

The isolation of allantoin (7), after lead peroxide oxidation of uric acid was followed by the recognition of other oxidation products, the main product of which are oxonic acid (8), allantoxaidine (9) and oxaluric acid (HjNOCHNCOCOjH). Their structures have been clarified by comprehensive studies using isotopically labeled compounds. ... 

Oxidation of uric acid (LXIV) and its iV-methylated derivatives at a graphite anode produces a quinonoid product (LXV), which adds water or another nucleophile across a C=N double bond to an unstable intermediate (LXVI), which reacts to products. From the oxidation of uric acid can be isolated, depending on pH, allantoin, 5-hydroxyhydan-toin, alloxan, and urea [362, 363] ... 

Isolation of Uric Acid from Urine (Section 410).—Add... 

Xanthine oxidase, which is capable of catalyzing the conversion of hypoxanthine and xanthine to uric acid, was first detected in 1882 by Horbaczewski (Hll), who noted that extracts of various tissues could catalyze the conversion of xanthine to uric acid. A similar enzyme was detected in milk (M15). These enzymes contain a flavin-adenine dinucleotide prosthetic group (C9). As a result of the essential nature of the flavin-adenine dinucleotide portion of the enzjmie, a striking parallelism was seen between the riboflavin content of the diet and the xanthine oxidase concentration in tissues of growing rats (DIO). The enzyme contains molybdenum. That the molybdenum is contained in a functionally important component has been demonstrated by several workers (G13, T5). Totter and his associates injected labeled molybdate into a cow, and then isolated the enzyme from the milk to show that the proportion between the molybdenum and flavin remained constant at a value of 0.5. Corran et al. (C9) postulated that the xanthine oxidase of milk is identical with the xanthine oxidase of liver, but the protein portions of the enzyme appear to differ. 

There were early reports that in patients with psoriasis there was a greater output of urinary uric acid (Bll) and increases in serum uric acid levels (E2). Eisen and Weissman showed that the increase in uric acid excreted was proportional to the amount of skin involved in the disease. This increase in uric acid may be partially the result of increased turnover of the diseased cells and release of their nucleic acid to the purine catabolic pool. There are other alterations in nucleic acids related to cellular metabolism in psoriasis. The ribonucleic acid concentration of psoriatic tissues is approximately 3 times that of normal skin, and the DNA can be as much as 13-14 times greater than in normal tissues (H8, W5). A fundamental change in the nature of psoriatic deoxyribonucleic acid was suggested by Steigleder et al. (S36), who isolated DNA s from psoriatic skin and from normal skin and... 

Since the discovery of hydantoin in 1861, when Baeyer isolated it in his uric acid studies, that system has been an important precursor of a-amino acids owing to its lability toward alkali, especially for those acids that are difficult to prepare by other methods.300 Furthermore, the stereochemical courses of the Bucherer-Bergs and Read methods of synthesis for hydantoins (Section II,E), permit the preparation of epimeric amino acids.301-305 Some of these amino acids have been tested as possible tumor growth inhibitors,306,307 as metabolism-resistant amino acid analogues for transport system studies,72,308... 

Caffeine (1,3,7-triniethylxanthine) is the well-known stimnlant present in tea and coffee. Uric acid, the end product of nucleic acid catabolism in humans, birds and reptiles (nric acid was one of the first heterocyclic compounds to be isolated as a pure substance, by the Swedish chemist Carl Scheele in 1776) is formed by the action of the enzyme xanthine oxidase. In cases of excess uric acid, deposition of crystals of uric acid can occur, leading to the joint pain known as gout, usually initially in the big toe and usually in males. 

Uric acid ribonucleoside (13) has been isolated from beef blood and liver. It is hydrolyzed in acid to uric acid and n-ribose, and a comparison of its ultraviolet spectrum with those of the four monomethyl-uric acids indicate that the D-ribose moiety is attached to the 9-nitrogen atom. Although it is reasonable to assume that the D-ribose moiety is in the... 

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