allopurinol and morin

Hyperuricemia is associated with a number of pathological conditions such as gout. Lowering of elevated uric acid level in the blood could be achieved by xanthine oxidase inhibitors and inhibitors of renal urate reabsorption. Some natural compounds isolated from herbs used in traditional Chinese medicine have been previously demonstrated to possess xanthine oxidase inhibitory activities. In the present investigation, morin (3,5,7,2',4'-pentahydroxyflavone), which occurs in the twigs of Morus alba L. documented in traditional Chinese medicinal literature to treat conditions akin to gout, was demonstrated to exert potent inhibitory action on urate uptake in rat renal brush-border membrane vesicles, indicating that this compound acts on the kidney to inhibit urate reabsorption. Lineweaver-Burk transformation of the inhibition kinetics data demonstrated that the inhibition of urate uptake was of a competitive type, with a K(i) value of 17.4 microM. In addition, morin was also demonstrated to be an inhibitor of xanthine oxidase. Lineweaver-Burk analysis of the enzyme kinetics indicated that the mode of inhibition was of a mixed type, with K(i) and K(ies) values being 7.9 and 35.1 microM, respectively. Using an oxonate-induced hyperuricemic rat model, morin was indeed shown to exhibit an in vivo uricosuric action, which could explain, in part at least, the observed hypouricemic effect of morin in these rats. The potential application of this compound in the treatment of conditions associated with hyperuricemia was discussed.

Topics: Alkaline Phosphatase; Animals; Antioxidants; Creatinine; Enzyme Inhibitors; Flavonoids; Hyperuricemia; In Vitro Techniques; Kidney; Kinetics; Male; Microvilli; Oxonic Acid; Rats; Rats, Sprague-Dawley; Uric Acid; Uricosuric Agents; Xanthine Oxidase

Free radicals are responsible for tissue injury in corneal preservation and transplantation. Morin hydrate, a flavonoid from Brazil wood, has been shown to be cytoprotective in several types of cells. The aim of this study was to investigate the effectiveness of morin hydrate on rabbit corneal endothelial cells against damage induced by oxyradicals and nitric oxide.. Corneal endothelial cell cultures were prepared from New Zealand white rabbits, using standard microcarrier technique. Two free-radical-generating systems were used-17 IU/L xanthine oxidase/1 mM hypoxanthine and 5 mM 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1, a nitric oxide-donating agent).. Over 95% of cultured corneal endothelial cells necrosed within 3.6 +/- 1.5 min after exposure to xanthine oxidase/hypoxanthine. Adding morin hydrate delayed cell necrosis to 5.8 +/- 0.3 min (0.25 mM morin hydrate), 13.3 +/- 5.0 min (0.5 mM), and 41.5 +/- 8.6 min (1.0 mM). Exposed to nitric oxide generated by SIN-1, cells necrosed by 9.5 +/- 2.5 min, versus 14.1 +/- 1.3 min (0.25 mM morin hydrate), 27.2 +/- 2.0 min (0.5 mM), and 43.3 +/- 5.4 min (1.0 mM). Morin hydrate significantly prolonged survival of cells compared to equimolar concentrations of purpurogallin, Trolox, or ascorbate (P < 0.01).. This study demonstrates that morin hydrate behaves as a broad-spectrum antioxidant: it scavenges not only xanthine oxidase/hypoxanthine-generated oxyradicals, but also nonenzymatic, nitrogen-derived radicals, better than those above mentioned antioxidants. This property of morin hydrate may help prevent free radical damage in corneal preservation solutions.

Topics: Animals; Antioxidants; Benzocycloheptenes; Cell Survival; Cells, Cultured; Chromans; Cytoprotection; Endothelium, Corneal; Flavonoids; Free Radical Scavengers; Free Radicals; Hypoxanthine; Molsidomine; Rabbits; Xanthine Oxidase

Oxygen-derived free radicals are known to injure the endothelium of aorta in diverse disorders. In this study we compared the cytoprotective effects of three flavonoids against oxyradical damage to porcine aortic endothelial cells in vitro. Cultured porcine aortic endothelial cells were exposed to oxyradicals generated by xanthine oxidase--hypoxanthine (XO-HP). The cytoprotective activities of morin, quercetin, and catechin on these systems were compared using established morphologic criteria. The results in the XO-HP system showed that morin at 0.125, 0.25, and 0.5 mM delayed cell necrosis to 27.4 +/- 1.3, 46.8 +/- 1.8, and longer than 70 min, respectively, compared with 12.0 +/- 1.3 min in the control group. These degrees of protection were significantly stronger than those provided by quercetin and catechin at corresponding concentrations (p < 0.01). Morin and quercetin were moderate inhibitors of xanthine oxidase on the basis of the oxygen consumption rate, whereas catechin at the same concentrations had little inhibitory effect. The data from uric acid formation and cytochrome c reduction were consistent with the oxygen consumption measurement for the three flavonoids.

Topics: Animals; Antioxidants; Aorta; Catechin; Cells, Cultured; Endothelium, Vascular; Flavonoids; Necrosis; Quercetin; Reactive Oxygen Species; Swine; Xanthine Oxidase

Morin hydrate is a bioactive pigment found in yellow Brazil wood. Recently, we reported that morin hydrate prolongs the survival of three types of cells from the human circulatory system against oxyradicals generated in vitro. The protection excels that given by equimolar concentrations of ascorbate, mannitol, and Trolox. Here, we demonstrate that, in vivo, morin hydrate at 5 mumol/kg actually reduced by > 50% the tissue necrosis in post-ischemic and reperfused rabbit hearts. Mechanistically, morin hydrate not only scavenges oxyradicals, but also moderately inhibits xanthine oxidase, a free-radical generating enzyme from the ischemic endothelium. Among other possibilities, morin hydrate appears to chelate some metal ions (e.g. Fe2+) in oxyradical formation, although this needs to be examined further. Nuclear magnetic resonance (at 500 mHz) and electron-impact mass spectrometry also supported a molecular formula of C15H10O7 for morin hydrate. Only by X-ray crystallography was it clearly revealed that there are two water molecules attached by intermolecular hydrogen bonds to a morin molecule. Also, the three rings of morin hydrate approach coplanarity. This conformation favours a delocalization of electrons after oxyradical reduction, making morin an effective antioxidant. Thus, we have documented some of the molecular properties and myocardial salvage effects of morin hydrate.

Topics: Animals; Antioxidants; Coronary Disease; Crystallography, X-Ray; Flavonoids; Heart; Magnetic Resonance Spectroscopy; Mass Spectrometry; Myocardial Reperfusion; Myocardium; Necrosis; Rabbits; Xanthine Oxidase

Cultured rat glomerular mesangial cells were damaged when exposed to oxyradicals generated either from xanthine oxidase plus hypoxanthine, or by superoxide radicals formed from menadione. Morin hydrate is an antioxidant extracted from yellow Brazil wood. When morin hydrate was added to cultured rat glomerular mesangial cells which were attacked by oxyradicals generated by xanthine oxidase plus hypoxanthine, the survival time of the cells was doubled. However, this protective effect of morin hydrate was less marked when the cells were attacked by menadione. Note that the protective effects of Trolox which is a polar analogue of vitamin E were miniscule relative to those of morin hydrate with both oxidants.

Topics: Animals; Antioxidants; Cell Survival; Cells, Cultured; Chromans; Flavonoids; Free Radicals; Glomerular Mesangium; Hypoxanthine; Hypoxanthines; Microscopy, Electron; Rats; Reactive Oxygen Species; Superoxides; Vitamin K; Xanthine Oxidase