Potent Xanthine Oxidase Inhibitor Research Articles

Synthesis of N-aryl-5-amino-4-cyanopyrazole derivatives as potent xanthine oxidase inhibitors

Some pyrazolo[3,4- d]pyrimidines, structurally related with allopurinol, a well known xanthine oxidase inhibitor, clinically used in the therapy of gout, have also been reported as potent inhibitors of xanthine oxidase and the growth of several human tumour cell lines. Considering the potential interest of this family of compounds, the aim of the present study was to synthesise and provide a full chemical characterization of new N-aryl-5-amino-4-cyanopyrazole derivatives and their corresponding pyrazolo[3,4- d]pyrimidines. Their biological activity pertaining to the xanthine oxidase inhibition and effect on the growth of three tumour cell lines (MCF-7, NCI-H460, and SF-268) are also provided. With only one exception, the synthesised compounds showed no effect on the growth of the three tumour cell lines. However, a strong xanthine oxidase inhibitory activity was observed for almost all pyrazolo[3,4- d]pyrimidines tested, revealing some of them IC 50 values below 1 μM. The results of the molecular docking studies of these compounds, against xanthine oxidoreductase are also described, providing an atomistic explanation of the differences in the inhibitory efficiency. MEP calculations were used to explain different inhibitory efficiency of similar inhibitors.

The screening and characterization of 6-aminopurine-based xanthine oxidase inhibitors

Xanthine oxidase (XO) is a key enzyme which can catalyze xanthine to uric acid causing hyperuricemia in humans. By using the fractionation technique and inhibitory activity assay, an active compound that prevents XO from reacting with xanthine was isolated from wheat leaf. It was identified by the Mass and NMR as 6-aminopurine (adenine). A structure–activity study based on 6-aminopurine was conducted. The inhibition of XO activity by 6-aminopurine (IC 50 = 10.89 ± 0.13 μM) and its analogues was compared with that by allopurinol (IC 50 = 7.82 ± 0.12 μM). Among these analogues, 2-chloro-6(methylamino)purine (IC 50 = 10.19 ± 0.10 μM) and 4-aminopyrazolo[3,4- d] pyrimidine (IC 50 = 30.26 ± 0.23 μM) were found to be potent inhibitors of XO. Kinetics study showed that 2-chloro-6(methylamino)purine is non-competitive, while 4-aminopyrazolo[3,4- d]pyrimidine is competitive against XO.

Synthesis of Thieno[3,2-e][1,2,4]Triazolo[1,5-c]pyrimidin-5(6H)-ones via Their [1,2,4]triazolo[4,3-c]pyrimidine Compounds as New Ring Systems by Dimroth-Type Rearrangement

- General and facile syntheses of thieno|3,2-e|[1,2,4|triazolo|,5-c|-pyrimidin-5(6H)-one (6a) and its 2-substituted derivatives (6b-j) produced by instantaneous isomerization of their |4,3-c| compounds (7a-j), which were prepared by condensation of 4-hydrazinothieno|2,3-d(pyrimidin-2(1H)-one (10) with appropriate triethyl orthoesters or by oxidative cyclization of 4-(benzylidenehydrazino)thieno|2,3-d(pyrimidin-2(1H)-ones (llc-j), are described as novel ring systems and as a new class of potential xanthine oxidase inhibitors. The | 1,5-c| isomers (6a-c) were further prepared by condensation of 3-amino-4-imino-2-oxo-1,2,3,4-tetrahydrothieno|2,3-d(pyrimidine (14) with appropriate triethyl orthoesters as a synthetic method for a reliable structure of the tricyclic ring systems.

Biochemical characterization of some pyrazolopyrimidine-based inhibitors of xanthine oxidase

Inhibition of xanthine oxidase-catalyzed conversion of xanthine to uric acid by various pyrazolopyrimidine-based inhibitors (allopurinol derivatives) was evaluated and compared with the standard inhibitor allopurinol. Three compounds out of the seven compounds used in the study were found to be reasonably good inhibitors of xanthine oxidase (XO). 4-Amino-6-mercaptopyrazolo-3,4-d-pyrimidine was found to be the most potent inhibitor of XO (IC50 = 0.600 +/- 0.009 microM). 4-Mercapto-1H-pyrazolo-3,4-d-pyrimidine (IC50 = 1.326 +/- 0.013 microM) and 4-amino-6-hydroxypyrazolo-3,4-d-pyrimidine (IC50 = 1.564 +/- 0.065 microM) also showed comparable inhibitory activity to that of allopurinol (IC50 = 0.776 +/- 0.012 microM). All three compounds showed competitive type of inhibition with comparable Ki values. Induction of the electron transfer reaction catalyzed by XO in the presence of these compounds monitored as reduction of 2,6-dichlorophenolindophenol (DCPIP) revealed that electron transfer by 4-amino-6-mercaptopyrazolo-3,4-d-pyrimidine is comparable to that obtained by allopurinol or xanthine. However, 4-mercapto-1H-pyrazolo-3,4-d-pyrimidine and 4-amino-6-hydroxypyrazolo-3,4-d-pyrimidine did not show DCPIP reduction. On the other hand, enzymatic reduction of cytochrome c in the presence of the three compounds was found to be insignificant and much less in comparison to allopurinol and xanthine. Therefore, both 4-amino-6-hydroxypyrazolo-3,4-d-pyrimidine and 4-mercapto-1H-pyrazolo-3,4-d-pyrimidine displayed the inhibitory property and also did not produce XO-mediated reactive oxygen species (ROS). Since 4-mercapto-1H-pyrazolo-3,4-d-pyrimidine was found to have some toxicity, the effect of 4-amino-6-hydroxypyrazolo-3,4-d-pyrimidine on the enzymatic formation of uric acid and ROS was investigated and it was found that this compound was inhibiting enzymatic generation of both uric acid and ROS. It can be noted that the standard inhibitor, allopurinol, inhibits uric acid formation but produces ROS.

Flow Injection Determination of Xanthine Oxidase Inhibitory Activity and Its Application to Food Samples

The enzyme xanthine oxidase (XOD) has been recognized as a key enzyme causing oxidative injury to tissues by ischemia-reperfusion. For this reason, XOD inhibitor, which effectively suppresses this enzyme, plays an important role in the inhibition of many diseases related to reactive oxygen species (ROS). In order to screen XOD inhibitors rapidly and conveniently, a novel assay using flow injection analysis (FIA) was proposed in the present investigation. To optimize the practical FIA system, we studied the effect of the reagent concentrations and the flow condition on the enzymatic reaction, and then selected the optimum condition as follows: 200-mU/ml XOD concentration, 0.5-mM xanthine concentration, 0.5-ml/min flow rate, and 2-m mixing coil length. Under this condition, a typical XOD inhibitor quercetin was determined in the concentration range 0.1 - 1.5 mM at a sampling frequency of 10 samples/h. Using the optimized FIA method, we determined the XOD inhibitory activity of some food samples: onions, apples and teas, which are the high sources of flavonoids known as the potential XOD inhibitors. Among these samples, tea leaves showed the highest activity, the second was onions and the lowest was apples. Based on the result of the assay, not only quercetin, but also other components in investigated samples, contributed to the XOD inhibitory activity.

HPTLC Densitometric Analysis of Orthosiphon stamineus. Leaf Extracts and Inhibitory Effect on Xanthine Oxidase Activity

ABSTRACTOrthosiphon stamineus. Benth. was cultivated at different locations in Malaysia to compare the xanthine oxidase inhibitory potential of the methanol extracts of the leaf. The extracts showed superoxide scavenging and xanthine oxidase inhibitory activities using in vitro. methods. By means of HPTLC densitometric technique and UV-Vis spectra, sinensetin (SEN) and 3′-hydroxy-5,6,7,4′-tetramethoxyflavone (TMF) concentrations in the extracts were found to vary from 0.09% to 0.36% and 0.02% to 0.10% of the day weight, respectively. The study provided evidence that the leaf of the plant can be useful for studying its anti-gout action.

6-(N-benzoylamino)purine as a novel and potent inhibitor of xanthine oxidase: Inhibition mechanism and molecular modeling studies

The inhibition of xanthine oxidase (XO) activity by the purine analogue 6-(N-benzoylamino)purine was evaluated and compared with the standard inhibitor, allopurinol and the parent compound adenine. 6-(N-benzoylamino)purine is a highly potent inhibitor of XO and comparable to allopurinol . Furthermore, 6-(N-benzoylamino)purine neither produced any enzymatic superoxide nor reduced XO by an electron transfer reaction unlike allopurinol. 6-(N-benzoylamino)purine is about 10000-fold more potent as a XO inhibitor compared to the only known purine analogue 8-bromoxanthine . 6-(N-Benzoylamino)purine is a competitive inhibitor of XO and the inhibition was not completely reversed even at 100 μM xanthine concentration. The calculated interaction energy [Ecomplex − (Eligand+Eprotein)] of − 30.5, − 22.6, and − 17.2 kcal/mol, respectively, of 6-(N-benzoylamino)purine, 8-bromoxanthine and the parent compound adenine provided the rationale for the better enzyme inhibitory activity of 6-(N-benzoylamino)purine. To understand the role of the benzamido group in the inhibition process, molecular docking studies were carried out and it was revealed that the hydrogen bonding interactions involving N-7 of the purine ring and the N–H of Arg880, N–H of the purine ring and OH of Thr1010, as well as non-bonded interactions of the benzamido group of 6-(N-benzoylamino)purine with amino acid residues Gly799, Glu802, Phe914, Ala1078, Ala1079 and Glu1261 in the active site of XO play an important role in the stabilization of the E–I complex.

Novel 3‐O‐Acyl Mesquitol Analogues as Free‐Radical Scavengers and Enzyme Inhibitors: Synthesis, Biological Evaluation and Structure—Activity Relationship.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel 3-O-acyl mesquitol analogues as free-radical scavengers and enzyme inhibitors: synthesis, biological evaluation and structure-activity relationship.

A new isomer of mesquitol (2,3-trans-3',4',7,8-tetrahydroxyflavan-3-ol) was isolated from Dichrostachys cinerea in excellent yields. It has shown free-radical scavenging property and alpha-glucosidase inhibitory activities but, it could not display xanthine oxidase inhibitory property. However, it was observed that acylation of 3-OH group significantly enhanced the alpha-glucosidase inhibition and displayed xanthine oxidase inhibitory potential. The structure activity relationship revealed that the degree of lipophilicity played a major role in improving enzyme inhibitory activities. A positive correlation was observed between enzyme inhibitory potential and acyl chain length (upto C-16) of aliphatic esters.

Induction of G1 phase arrest in MCF human breast cancer cells by pentagalloylglucose through the down-regulation of CDK4 and CDK2 activities and up-regulation of the CDK inhibitors p27 Kip and p21 Cip

Pentagalloylglucose (5GG) is a potent and specific inhibitor of NADPH dehydrogenase or xanthine oxidase. In our previous study, we showed that 5GG was able to induce apoptosis in HL-60 cells in a time- and concentration-dependent manner via the activation of caspase-3. Recently, we found that 5GG was capable of perturbing the cell cycle of the human breast cancer cell line MCF-7. DNA flow cytometric analysis showed that 5GG exhibited the ability of blocking MCF-7 cell cycle progression at the G1 phase. The level of several G1 phase-related cyclins and cyclin-dependent kinases did not change in these cells during a 24-hr exposure to 5GG. However, the activity of cyclin E/CDK2 was decreased in a concentration- and time-dependent manner and the activity of cyclin D/CDK4 was inhibited when serum-starved synchronized cells were released from synchronization. p27 Kip and p21 Cip, inhibitors of cyclin/CDK complexes in G1-phase, were gradually increased after 5GG treatment in a time-dependent manner and the induction of p21 Cip was correlated with an increase in p53 levels. These results suggest that the suppression of cell-cycle progression in the G1 phase by 5GG was mediated in MCF-7 cells, at least in part, by either the inhibition of cyclin D/CDK4 and cyclin E/CDK2 activity or the induction of the CDK inhibitors p27 Kip and p21 Cip.

Effect of Gamma Irradiation on the Biological Activities and Color Changes of Ethanol Extracts Lonicera japonica

Effects of irradiation on color removal, tyrosinase inhibition, xanthine oxidase inhibition and nitrite scavenging capacity of Lonicera japonica extracts were evaluated. Lonicera japonica extracts were irradiated at 10, 20, and 30 kGy. Hunter color L^*- and a^*-values increased but b^*-values decreased dose-dependently following irradiation. The extracts were potent inhibitors of tyrosinase and xanthine oxidase. Tyrosinase inhibition was higher in the irradiated sample than non-irradiated, and subsequently increased with increasing irradiation doses. The extracts had a higher inhibitory effect against xanthine oxidase, and the effect was not changed by irradiation. Nitrite scavenging capacity was the highest in the extract at pH 1.2, and was not significantly affected by irradiation. These results indicate that gamma irradiation may not influence the biological activities of Lonicera japonica extracts when irradiated up to 30 kGy. Furthermore, color of the extracts can be improved to have improved applicability for the food and cosmetic industries without any adverse change in biological functions.

ChemInform Abstract: 2‐Alkyloxyalkylthiohypoxanthines as New Potent Inhibitors of Xanthine Oxidase.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

2-Styrylchromones As Novel Inhibitors of Xanthine Oxidase. A Structure-activity Study

The purpose of this study was the evaluation of the xanthine oxidase (XO) inhibition produced by some synthetic 2-styrylchromones. Ten polyhydroxylated derivatives with several substitution patterns were synthesised, and these and a positive control, allopurinol, were tested for their effects on XO activity by measuring the formation of uric acid from xanthine. The synthesised 2-styrylchromones inhibited xanthine oxidase in a concentration-dependent and non-competitive manner. Some IC 50 values found were as low as 0.55 μM, which, by comparison with the IC 50 found for allopurinol (5.43 μM), indicates promising new inhibitors. Those 2-styrylchromones found to be potent XO inhibitors should be further evaluated as potential agents for the treatment of pathologies related to the enzyme's activity, as is the case of gout, ischaemia/reperfusion damage, hypertension, hepatitis and cancer.

2-Alkyloxyalkylthiohypoxanthines as new potent inhibitors of xanthine oxidase

The title compounds were prepared and tested as xanthine oxidase (XO) inhibitors. Results evidenced that potency was related to the position of the oxygen atom in the 2-linear chain and that it grew with distance from the sulfur atom until it became equipotent to 2- n-hexylthiohypoxanthine. Enzymatic oxidation on C(2) occurred in the 8-alkylthiohypoxanthines. On the contrary, oxidation on C(8) did not occur in the 2-alkythioderivatives, demonstrating that the chain forced these molecules to form a complex with molybdenum(VI) involving only the N(3) and N(9) nitrogen atoms.

Syntheses and biological evaluation of new glyco-modified angucyclin-antibiotics

The synthesis of novel aquayamycin-derived angucycline antibiotics 13a– d has been achieved. Glycosylation of aquayamycin ( 6) using 2-selenoglycosyl acetate 7 as glycosyl donor proceeded in excellent yield but attempts to reductively remove the selenyl group led to rearrangement or further aromatization of the aglycon. As a consequence of these results, it became possible to prepare urdamycinone B ( 10) starting from aquayamycin ( 6). In addition, silyl protected d-olivals 12a, b were attached to the C-glycoside domain of aquayamycin ( 6) under protic conditions. As expected, the hydroxy and phenol groups of the benz[ a]anthracene framework of 6 did not react under the glycosylation conditions employed. Stepwise removal of the silyl protecting group starting with tetrabutyl ammonium fluoride followed by use of the HF/pyridine complex suppressed a possible rearrangement of the aglycon and successfully terminated the sequence. The new angucycline-antibiotics 13a and 13b are some of the most potent xanthine oxidase inhibitors known and show cytotoxic activity with ED 50-values in the range of 12.6–2.9×10 −6 M

Inhibition of xanthine oxidase and suppression of intracellular reactive oxygen species in HL-60 cells by theaflavin-3,3'-digallate, (-)-epigallocatechin-3-gallate, and propyl gallate.

The inhibitory effects of five tea polyphenols, namely theaflavin (TF1), theaflavin-3-gallate (TF2), theaflavin-3,3'-digallate (TF3), (-)-epigallocatechin-3-gallate (EGCG), and gallic acid, and propyl gallate (PG) on xanthine oxidase (XO) were investigated. These six antioxidant compounds reduce oxidative stress. Theaflavins and EGCG inhibit XO to produce uric acid and also act as scanvengers of superoxide. TF3 acts as a competitive inhibitor and is the most potent inhibitor of XO among these compounds. Tea polyphenols and PG all have potent inhibitory effects (>50%) on PMA-stimulated superoxide production at 20 approximately 50 microM in HL-60 cells. Gallic acid (GA) showed no inhibition under the same conditions. At 10 microM, only EGCG, TF3, and PG showed significant inhibition with potency of PG > EGCG > TF3. The superoxide scavenging abilities of these six compunds are as follows: EGCG > TF2 > TF1 > GA > TF3 > PG. PG was the most potent inhibitor of PMA-stimulated H(2)O(2) production in HL-60 cells. The order of H(2)O(2) scavenging ability was TF2 > TF3 > TF1 > EGCG > PG > GA. Therefore, the antioxidative activity of tea polyphenols and PG is due not only to their ability to scavenge superoxides but also to their ability to block XO and related oxidative signal transducers.

Effect of losartan and furosemide on the urinary excretion of oxypurinol and uric acid.

Losartan potassium (losartan) is an angiotensin II receptor antagonist used for the treatment of hypertension1, which opposes the action of angiotensin II at the AT1 receptor. Losartan has a uricosuric action, which depends on the inhibition of uric acid reabsorption in the proximal tubules2. On the other hand, furosemide is diuretic and is used for the treatment of heart failure, hypertension and edema. It inhibits the absorption of chloride and sodium at Henle’s loop, resulting in an increase in the rate of urine formation together with natriuresis. Further, it increases the concentration of serum uric acid, which is attributable to a furosemide-induced decrease in extracellular fluid and the urinary excretion of uric acid. Many previous studies 5-7 have demonstrated that glucagon, amino acids, benzbromarone, and probenecid increase the urinary excretion of oxypurinol and uric acid, suggesting that latter share a renal transport pathway. With these findings in mind, we speculated that losartan may increase the urinary excretion of oxypurinol, while furosemide may have the opposite effect causing its urinary excretion to decrease. Oxypurinol is a metabolite of allopurinol, which is used for the treatment of hyperuricemia. Although both allopurinol and oxypurinol are potent inhibitors of xanthine oxidase, the biological half time of oxypurinol is longer than that of allopurinol. Accordingly, the

Novel xanthine oxidase inhibitor studies. Part 3. Convenient and general syntheses of 3-substituted 7H-pyrazolo[4,3-e]-1,2,4-triazolo[4,3-c]pyrimidin-5(6H)-ones as a new class of potential xanthine oxidase inhibitors

Convenient and general syntheses of 3-substituted 7H-pyrazolo[4,3-e]-1,2,4-triazolo[4,3-c]pyrimidin-5(6H)-ones (12), a new class of potent xanthine oxidase inhibitors, involving the oxidative cyclisation of 6-substituted 4-alkylidenehydrazino- or 4-arylmethylidenehydrazino-1H-pyrazolo[3,4-d]pyrimidines (3 and 11) with 70% nitric acid as the key step, are reported. The hydrazones 3 and 11 were obtained by a versatile synthetic route via the key intermediates, 6-chloro-4-hydrazino-1H-pyrazolo[3,4-d]pyrimidine 2 or oxypurinol 4, starting from 2,4,6-trichloropyrimidine-5-carbaldehyde 1. Their inhibitory activities against bovine milk xanthine oxidase in vitro are also described; i.e. the pyrazolotriazolopyrimidines 12 were several hundred times more potent than allopurinol.

ChemInform Abstract: Facile and General Syntheses of 3‐ and/or 5‐Substituted 7H‐Pyrazolo[4,3‐e]‐1,2,4‐triazolo[4,3‐c]pyrimidines as a New Class of Potential Xanthine Oxidase Inhibitors.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Facile and General Syntheses of 3‐ and/or 5‐Substituted 7‐β‐D‐Ribofuranosyl‐7H‐[1,2,4]triazolo[3,4‐i]purines as a New Class of Potential Xanthine Oxidase Inhibitors.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.