Uric acid Properties

The process of reabsorption depends on the HpophiHc—hydrophiHc balance of the molecule. Charged and ioni2ed molecules are reabsorbed slowly or not at all. Reabsorption of acidic and basic metaboHtes is pH-dependent, an important property in detoxification processes in dmg poisoning. Both passive and active carrier-mediated mechanisms contribute to tubular dmg reabsorption. The process of active tubular secretion handles a number of organic anions and cations, including uric acid, histamine, and choline. Dmg metaboHtes such as glucuronides and organic acids such as penicillin are handled by this process. 

Enzymes are proteins of high molecular weight and possess exceptionally high catalytic properties. These are important to plant and animal life processes. An enzyme, E, is a protein or protein-like substance with catalytic properties. A substrate, S, is the substance that is chemically transformed at an accelerated rate because of the action of the enzyme on it. Most enzymes are normally named in terms of the reactions they catalyze. In practice, a suffice -ase is added to the substrate on which die enzyme acts. Eor example, die enzyme dial catalyzes die decomposition of urea is urease, the enzyme dial acts on uric acid is uricase, and die enzyme present in die micro-organism dial converts glucose to gluconolactone is glucose oxidase. The diree major types of enzyme reaction are ... 

Uric acid is odourless in spite of three carbonyl groups, four trivalent nitrogen atoms and a double bond, and that it is similarly colourless in spite of four chromophores. Measurements of its refractive and dispersive properties indicate that it is a saturated body which suggests that molecular attraction exists between the various groups. 

The first CNT-modified electrode was reported by Britto et al. in 1996 to study the oxidation of dopamine [16]. The CNT-composite electrode was constructed with bro-moform as the binder. The cyclic voltammetry showed a high degree of reversibility in the redox reaction of dopamine (see Fig. 15.3). Valentini and Rubianes have reported another type of CNT paste electrode by mixing CNTs with mineral oil. This kind of electrode shows excellent electrocatalytic activity toward many materials such as dopamine, ascorbic acid, uric acid, 3,4-dihydroxyphenylacetic acid [39], hydrogen peroxide, and NADH [7], Wang and Musameh have fabricated the CNT/Teflon composite electrodes with attractive electrochemical performance, based on the dispersion of CNTs within a Teflon binder. It has been demonstrated that the electrocatalytic properties of CNTs are not impaired by their association with the Teflon binder [15]. 

A large number of nonenzymatic compounds, including tocopherols, caroti-noids, vitamins C and D, steroids, ubiquinones, thiols, uric acid, bilirubin, ino-sine, taurine, pyruvate, CRP, and so on, demonstrate qualitative antioxidant properties under experimental conditions. However, the quantitative relevance of most findings remains unclear. 

Physical Properties. When crystallized from aqueous solutions above 5°C natural (R-K-.R" l-tar(uric acid is obtained in the anhydrous lornt. Below 5 C. tartaric acid forms a inunohydrnte which is unstable at room temperature. Some of the physical properties of i R-R .R l-tartaric aeid are listed in Table 3. 

Other antioxidant species are synthesized by cells like uric acid, ubiquinol or thiols (cystein, homocystein, etc.). In addition, many compounds found in food display antioxidant properties retinol (vitamin A) and its precursor /(-carotene, and polyphenols (flavonoids, etc.). Figure 8.2 shows the apparent standard potential of some LMWA and ROS explaining the spontaneous oxido-reduction reactions at the origin of the antioxidant protection system. 

On the other hand, drugs may inhibit the metabolism of other drugs. For example, allopurinol (a xanthine oxidase inhibitor that inhibits the synthesis of uric acid) increases the effectiveness of anticoagulants by inhibiting their metabolism. Chloramphenicol (a potent inhibitor of microsomal protein synthesis) and cimetidine (an H2-receptor blocker used in acid-pepsin disease) have similar properties. In addition, drugs may compete with each other in metabolic reactions. In methyl alcohol (methanol) poisoning, ethyl alcohol may be given intravenously to avert methanol-induced blindness and minimize the severe acidosis. Ethyl alcohol competes with methyl alcohol for... 

Although equivalent to aspirin as an effective analgesic and antipyretic agent, acetaminophen differs in that it lacks anti-inflammatory properties. It does not affect uric acid levels and lacks... 

The strong alterative properties are made considerable use of in rheumatic and general uric acid disorders, as well as various skin diseases. Decoction of 1/2 ounce to 1 1/2 pints (reduced to 1 pint) is taken in tablespoonful doses four times daily. 

The diuretic property of celery has been used to prepare herbal medicine (Houghton, 1995). The ripe seeds, herb and root are diuretic (Lust, 1983 Chiej, 1984 Grieve, 1984). The seeds are used mainly as a diuretic and can help clear toxins from the system, especially in cases of gout where uric acid crystals collect in the joints. Root tinctures have been used to cure urinary disorders, such as urinary stones, and used as a kidney stimulant and cleanser. Fresh juice from the whole plant is also used as a cure for urinary tract inflammations and urethritis (http //www.innvista.com/health/herbs/ celery.htm). The herb is used against kidney complaints (Launert, 1981). 

Understand the properties of purine and pyrimidine bases and nucleosides, and nucleotides with varying amounts of phosphate. Recognize the structures of the various xanthines, cyclic nucleotides, uric acid, and bases found in nucleic acids. 

The lung also possesses nonenzymatic antioxidants such as vitamin E, beta-carotene, vitamin C, and uric acid. Vitamin E is lipid-soluble and partitions into lipid membranes, where it is positioned optimally for maximal antioxidant effectiveness. Vitamin E converts superoxide anion, hydroxyl radical, and lipid peroxyl radicals to less reactive oxygen metabolites. Beta-carotene also accumulates in cell membranes and is a metabolic precursor to vitamin A. Furthermore, it can scavenge superoxide anion and react directly with peroxyl-free radicals, thereby serving as an additional lipid-soluble antioxidant. Vitamin C is widely available in both extracellular and intracellular spaces where it can participate in redox reactions. Vitamin C can directly scavenge superoxide and hydroxyl radical. Uric acid formed by the catabolism of purines also has antioxidant properties and primarily scavenges hydroxyl radical and peroxyl radicals from lipid peroxidation. 

Uric acid in very low concentrations, very strongly absorbs UV radiation and for this reason, has been used to protect various FD C colors against fading when they will be probably exposed to direct sunlight (112). Uric acid has been found to enhance the photostability of solutions of colchicine (70) and FD C Blue No. 2 (82,113). Sodium urate, the neutral salt of uric acid, has a photoprotective effect on solutions of metronidazole (68), doxorubicin hydrochloride (77), and physostigmine sulfate (108). In addition to its photon-absorbing property, uric acid has been reported to also possess antioxidant quality (114). 

The examples provided above indicate that single enantiomers are not always better alternatives to their respective racemates. Another interesting example is 5-dimethyl-sulphamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxilic acid, a racemic diuretic whose diuretic activity is attributed to the S(—)-enantiomer, while theR(+)-enantiomer has uricosuric properties that suppress the S-enantiomer-induced side-effect of elevated blood uric acid (21). It is not known if marripulation of the S R ratio of this drug, as is seen for indocrinone (below), results in a better diuretic agent. 

The diuretic properties of indocrinone have been reported to improve by manipulation of the enantiomers rario (22) Although the diuretic property is predominantly ascribed to R(-)-indocrinone, both enantiomers possess urisocuric activity. The uricosuric effect is desirable as it counteracts the diuretic-induced rise in plasma uric acid concentration. However, this property of racemic indocrinone is transient. Examination of the overall pharmacodynamic profile of various formulations of indocrinone suggests that the patients remain isouricemic during a 7-day treatment period with an R S ratio of 10 40. 

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