Biomedical subjects

S Y Sheu

Publications and source records attributed to S Y Sheu.

25 records · Page 2Linked to original sources

PubMedDate not supplied

Inhibition of xanthine oxidase by benzothiazinone analogues.

Fourteen synthetic benzothiazinone analogues were tested for their inhibitory effects on xanthine oxidase. The enzyme, xanthine oxidase (XO) catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid, which has a lambda max of 295 nm, forming the basis for a spectrophotometric assay for the activity of xanthine oxidase. The results showed that 2-amino-4H-1,3-benzothiazine-4-one (1), 2-guanidino-4H-1,3-benzothiazin-4-one (2) and rhodanine (3) display inhibitory effects on xanthine oxidase with an order of activity of IC50 = 5.54, 5.60 and 121.40 microM respectively. The apparent inhibition constants (Ki) were 5.12, 19.47 and 206.23 microM, and induced non-competitive, mixed type (non-competitive-uncompetitive) and mixed type (non-competitive-uncompetitive) inhibitions respectively with respect to the substrate xanthine.

Enzyme Inhibitors↗

PubMedDate not supplied

Benzophenones as xanthine oxidase inhibitors.

Eight synthetic benzophenones were tested for their inhibitory effects on xanthine oxidase (XO). The enzyme, XO catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid, which has a lambda max of 295 nm, forming the basis for a spectrophotometric assay for the activity of XO. The results showed that 2,2',4,4'-tetrahydroxybenzophenone (6), 3,4,5,2',3',4'-hexahydroxybenzophenone (8) and 4,4'-dihydroxybenzophenone (3) displayed the inhibitory effects on XO with an order of activity of IC50 = 47.59, 69.40 and 82.94 microM, respectively. The apparent inhibition constants (Ki) of (8) and (3) were 15.61 and 64.86 microM respectively, and both of them induced mixed type (non-competitive-uncompetitive) inhibitions of the substrate xanthine.

Benzophenones↗

PubMedDate not supplied

Inhibitory effects of plant growth regulators on xanthine oxidase.

Several plant hormones and analogues were tested for their inhibitory effects on xanthine oxidase. The flavoprotein enzyme, xanthine oxidase, catalyses the oxidation of hypoxanthine to xanthine and then xanthine to uric acid which has lambda max 295 nm. Uric acid was thus the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that trans-zeatin displayed the strongest activity (IC50 = 23.5 muM) on xanthine oxidase inhibition, followed by indole-3-acrylic acid (IC50 = 136.0 muM) and then by the mixed isomers of zeatin (trans-zeatin and cis-zeatin) (IC50 = 198.65 muM). Trans-zeatin induced an uncompetitive inhibition of the enzyme with respect to the substrate xanthine and the apparent inhibition constant (Ki) was 5.09 muM. However, zeatin riboside was inactive. Since xanthine oxidase serum levels are increased in hepatitis, mild hepatic intoxication, tumours brain tissues, and DNA damage induced by cytotoxic agents, it is expected that trans-zeatin may be useful for the treatment of these diseases as well as gout which is caused by deposition of uric acid in the joints and oxidative damage of tissue caused by generation of superoxide anion radical.

Enzyme Inhibitors↗

PubMedDate not supplied

Inhibition of xanthine oxidase by cytokinins and related substances.

Fourteen cytokinins were tested for their inhibitory effects on xanthine oxidase. The enzyme, xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid which has lambda max of 295 nm, forming the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that adenine-HCl, N6-(2-isopentenyl)-adenine, purine and DL-dihydrozeatin displayed very potent activities (IC50 = 1.92, 10.99, 60.98 and 86.36 microM respectively). Their apparent inhibition constants (Ki) were 2.20, 17.99, 13.59 and 115.62 microM, and induced competitive, uncompetitive, competitive and non-competitive type inhibitions respectively with respect to the substrate xanthine.

Adenine↗

PubMedDate not supplied

Inhibition of xanthine oxidase by synthetic cytokinin analogues.

Thirteen synthetic cytokinin analogues were tested for their inhibitory effects on xanthine oxidase. The enzyme, xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid, which has a gamma max of 295 nm, forming the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that 8-azaadenine(1), 4-amino-6-hydroxypyrazolo [3,4-d] pyrimidine(4), 4-amino-6-mercaptopyrazolo [3,4-d] pyrimidine(5) and 4-aminopyrazolo [3,4-d] pyrimidine(6) display inhibitory effects on xanthine oxidase with an order of activity of IC50 = 0.54, 5.91, 8.17 and 25.46 microM, respectively. Their apparent inhibition constants (Ki) were 0.66, 1.54, 6.61 and 26.79 microM, and induced mixed(competitive-non-competitive), competitive, mixed (competitive-non-competitive), and competitive types of inhibition respectively, with respect to the substrate xanthine.

Cytokinins↗

PubMedDate not supplied

Inhibition of xanthine oxidase by hydroxylated anthraquinones and related compounds.

Eighteen anthraquinones and related compounds were tested for their inhibitory effects on xanthine oxidase. The enzyme, xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid, which has a lambda max of 295nm, forming the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that anthrarobin and purpurin showed moderate effects on xanthine oxidase inhibition (IC50 = 68.35 and 105.13 microM; Ki = 122.38 and 130.49 microM respectively), and both of them induced mixed type (competitive-non-competitive) inhibition with respect to the substrate xanthine.

Anthraquinones↗

PubMedDate not supplied

Inhibition of xanthine oxidase by purpurogallin and silymarin group.

Thirteen phenolic compounds were tested for their inhibitory effects on xanthine oxidase. The enzyme xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and of xanthine to uric acid, which has lambda max of 295 nm, forming the basis for a spectrophotometric assay of the activity of xanthine oxidase. The results showed that purpurogallin and silymarin group displayed the inhibitory effects on xanthine oxidase (IC50 = 2.96 +/- 0.12 and 27.58 +/- 3.48 microM, respectively). Their apparent inhibition constants (Ki) were 1.16 and 5.85 microM, and induced uncompetitive and mixed type (non-competitive-uncompetitive) inhibitions respectively, with respect to the substrate xanthine.

Antioxidants↗