Xanthine

About: Xanthine is a research topic. Over the lifetime, 4046 publications have been published within this topic receiving 129820 citations. The topic is also known as: Xanthine.

Free radical scavenging reactions and phytochemical analysis of triphala, an ayurvedic formulation

Abstract: In order to understand the factors responsible for the potent antioxidant and radioprotecting ability of triphala, it has been evaluated for radical scavenging ability, xanthine oxidase inhibitory activity and phytochemical (phenolics) content. The radical scavenging experiments were carried out using fast reaction kinetic tools and the reactivity of triphala towards different radicals such as hydroxyl radicals, superoxide radicals, DPPH and ABTS • •was determined. When triphala was tested for superoxide radical scavenging activity using xanthine and xanthine oxidase assay, it was observed that in addition to reacting with superoxide radical, it also inhibited uric acid formation, indicative of xanthine oxidase enzyme inhibitory activity. Phytochemical ana lysis showed that triphala is rich in phenols/polyphenols (38 ± 3%) and tannins (35 ± 3%), while flavonoids were found to be absent. HPLC analysis showed that triphala contains 73 ± 5 mg gallic acid per gram of triphala, which was found to increase to 150 ± 5 mg/g upon acid hydrolysis. Relevance of these studies to the antioxidant and radio protection properties of triphala has also been discussed.

Role of hydrogen peroxide in the cytotoxicity of the xanthine/xanthine oxidase system.

Abstract: 1. The survival of mammalian epithelial cells exposed in vitro to the xanthine/xanthine oxidase system in phosphate-buffered saline (PBS) or serum-containing medium (SCMEM) was investigated. 2. The cytotoxic effect observed depended on the composition of the medium in which the enzymic reaction was carried out; a surviving fraction of 5 x 10(-5) was found for cells exposed in PBS and 5.2 x 10(-1) for those in SCMEM. 3. The cytotoxic product(s) formed by the xanthine/xanthine oxidase system was relatively stable in PBS; survival of cells incubated after completion of the enzymic reaction was always less than that found for cells exposed during the reaction in the same system. 4. Superoxide dismutase or mannitol present during the enzymic reaction did not inhibit the cytotoxic effect. 5. NaN3 (a single-oxygen quencher and a catalase inhibitor) added to the system in SCMEM caused a reduction in survival to the level observed for cells exposed to the enzymic reaction in PBS. 6. Catalase completely protected cells, but no protection was observed when both catalase and NaN3 were present in the reaction mixture. 7. A similar cytotoxic effect was produced when cells were treated with H2O2 alone. 8. The rate of H2O2 decomposition in medium was accelerated by the presence of serum, but this was completely inhibited by NaN3. 9. It is concluded that H2O2 is the major cytotoxic product formed by the xanthine/xanthine oxidase system.

Uricase, Guanase, and Xanthine Oxidase from the Fat Body of the Cockroach, Leucophaea Maderae

Abstract: Uricase was isolated from homogenates of the fat body of the nymph and adult cockroach, Leucophaea maderae, by the method of Praetorius (1949). Its activity is of the first-order with an average Michaelis constant of 1.7 × 105 moles per liter at a pH of 9.2. Guanase was isolated from the fat body by the method of Kalckar (1947) and its activity measured spectrophotometrically. Xanthine oxidase was found in homogenates of the nymph and adult cockroach. Nymphal homogenates demonstrated a higher ability to oxidize the oxypurines than those of the adult. Homogenates of both stages were more active with hypoxanthine than with xanthine as the substrate.