Synthesis of some 5-phenylisoxazole-3-carboxylic acid derivatives as potent xanthine oxidase inhibitors

Xanthine oxidase inhibitors beyond allopurinol and febuxostat; an overview and selection of potential leads based on in silico calculated physico-chemical properties, predicted pharmacokinetics and toxicity

Xanthine oxidase (XO), a versatile metalloflavoprotein enzyme, catalyzes the oxidative hydroxylation of hypoxanthine and xanthine to uric acid in purine catabolism while simultaneously producing reactive oxygen species. Both lead to the gout-causing hyperuricemia and oxidative damage of the tissues where overactivity of XO is present. Over the past years, significant progress and efforts towards the discovery and development of new XO inhibitors have been made and we believe that not only experts in the field, but also general readership would benefit from a review that addresses this topic. Accordingly, the aim of this article was to overview and select the most potent recently reported XO inhibitors and to compare their structures, mechanisms of action, potency and effectiveness of their inhibitory activity, in silico calculated physico-chemical properties as well as predicted pharmacokinetics and toxicity. Derivatives of imidazole, 1,3-thiazole and pyrimidine proved to be more potent than febuxostat while also displaying/possessing favorable predicted physico-chemical, pharmacokinetic and toxicological properties. Although being structurally similar to febuxostat, these optimized inhibitors bear some structural freshness and could be adopted as hits for hit-to-lead development and further evaluation by in vivo studies towards novel drug candidates, and represent valuable model structures for design of novel XO inhibitors.

2-Benzamido-4-methylthiazole-5-carboxylic Acid Derivatives as Potential Xanthine Oxidase Inhibitors and Free Radical Scavengers

The new chemical entities febuxostat and topiroxostat have been approved by the US Food and Drug Administration, opening new avenues for exploiting different heterocycles other than purines as xanthine oxidase (XO) inhibitors. A different series of substituted 2-benzamido-4-methylthiazole-5-carboxylic acid derivatives (5a-r) was synthesized and characterized by the collective use of IR, ¹ H and ¹³ C NMR, and mass spectroscopy, for the treatment of gout and hyperuricemia. In vitro studies of the synthesized derivatives revealed that the presence of a fluoro group at the para position in 5b (IC50 = 0.57 μm) and a chloro group in 5c (IC50 = 0.91 μm) signifies excellent XO inhibitory activity among the series, along with their DPPH free radial scavenging activity. In vivo serum uric acid inhibition studies established that 5b and 5c displayed 62 and 53% uric acid inhibition, respectively. Studies on enzyme kinetics indicated that 5b acts as a mixed type inhibitor. In silico prediction by various softwares also helped in the recognition of potent XO inhibitors.

Antihyperuricemic effects of thiadiazolopyrimidin-5-one analogues in oxonate treated rats

Hyperuricemia is a risk factor for not only gout, but also to a variety of disorders that affect the vital organ systems of the human body. The xanthine oxidase (XO) is the key enzyme in the production of uric acid and its inhibition can inhibit hyperuricemia. Although, XO inhibitor allopurinol is widely prescribed antigout agent but its use is not without any side effects. Previously, we described the synthesis of four novel thiadiazolopyrimidin-5-one analogues as effective XO inhibitors and molecular docking studies also confirmed this. When these analogues were tested in potassium oxonate treated rats, their serum uric acid and creatinine levels were dropped significantly from 4.85±0.03 mg/dl to 1.21±0.01 mg/dl and 0.92±0.02 mg/dl to 0.40±0.02 mg/dl respectively. Among the pyrimidine analogues tested, 6a was most potent. Histological examinations of both liver and kidney tissues exhibited severe necrosis in oxonate treated rats and pyrimidine analogues could significantly attenuate this with a correlative inhibitory profile of hepatic XO from the same rats. Our results demonstrate antihyperuricemic effect of novel thiadiazolopyrimidin-5-one analogues in oxonate treated rats, which can be further explored not only as antigout therapeutics but also in other systems where hyperuricemia is the driving cause of the disease.

Synthesis and bioevaluation of 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acids as potent xanthine oxidase inhibitors

A series of 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acid derivatives (8a-f, 9a-m) were synthesized and evaluated for inhibitory activity against xanthine oxidase in vitro. Structure-activity relationship analyses have also been presented. Most of the target compounds exhibited potency levels in the nanomolar range. Compound 9e emerged as the most potent xanthine oxidase inhibitor (IC50 = 5.5 nM) in comparison to febuxostat (IC50 = 18.6 nM). Steady-state kinetics measurements with the bovine milk enzyme indicated a mixed type inhibition with Ki and Ki' values of 0.9 and 2.3 nM, respectively. A molecular modeling study on compounds 9e was performed to gain an insight into its binding mode with xanthine oxidase, and to provide the basis for further structure-guided design of new non-purine xanthine oxidase inhibitors related with 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acid scaffold.

Analysis of patents on anti-gout therapies issued in China

INTRODUCTION

The incidence of gout and hyperuricemia has been increasing. The demand for new anti-gout therapies today presents exciting opportunities to organizations and individuals offering such products.

AREAS COVERED

This review analyzes the patents of anti-gout products to help pharmaceutical companies and individuals in the patenting of potential candidate drugs for gout treatment in China.

EXPERT OPINION

In this review, 786 patents were found, among which, 215 are in the protection period. The latter group of patents includes 183 patents for traditional Chinese medicines (TCM, 85%), 30 for synthetic compounds (14%) and 2 for combinations of synthetic compounds and TCM (CST). Among the TCM patents, 84% contain various dosage formulae for different Chinese medicines, 13% are herbal extracts and only 7 patents are from herbal extract derivatives. Synthetic compound patents mainly target xanthine oxidase, urate transporter 1 and uric acid oxidase. Searching for new targets and drugs acting on multiple targets should provide a new stimulus in the field of synthetic compound patents. CST has the smallest proportion of Chinese anti-gout patents, although it is still in the test stage and has not been widely accepted, but has provided a new direction for the field of anti-gout patents.

3-Benzyl-1-{[3-(4-chloro-phen-yl)isoxazol-5-yl]meth-yl}-1H-benzimidazol-2(3H)-one

In the title compound, C24H18ClN3O2, the benzimidazole plane is nearly perpendicular to the phenyl ring and to the isoxazole ring, making dihedral angles of 75.95 (7) and 73.04 (8)°, respectively, but the two residues point in opposite directions with respect to the benzimidazole plane. The dihedral angle between the chloro-phenyl and isoxazole rings is 7.95 (8)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds into inversion dimers.

Synthesis and biological evaluation of some 4-functionalized-pyrazoles as antimicrobial agents

1,3-Diaryl-4-formylpyrazoles 8 bearing benzenesulfonamide moiety at position-1 were synthesized as important intermediates following Vilsmeier-Haack strategy. Aldehyde moiety of 4-formylpyrazole was then converted into carboxylic acid 9, cyano 10 and carbothioamide 11 using established procedures. Out of these 4-functionalized pyrazoles, pyrazole-4-carboxylic acids 9 and carbothioamides 11 were evaluated for their in vitro antibacterial activity against four pathogenic bacterial strains namely, Staphylococcus aureus, Bacillus subtilis (Gram-positive), Escherichia coli, Pseudomonas aeruginosa (Gram-negative), and in vitro antifungal activity against two pathogenic fungal strains namely, Aspergillus niger and Aspergillus flavus. Three tested compounds, 9e, 11b and 11f exhibited moderate antibacterial activity against Gram-positive bacteria and 9g showed moderate antifungal activity against the tested fungi. However, none of the compounds showed any activity against Gram-negative bacteria.

Synthesis and xanthine oxidase inhibitory activity of 7-methyl-2-(phenoxymethyl)-5H-[1,3,4]thiadiazolo[3,2-a]pyrimidin-5-one derivatives

An elevated level of blood uric acid (hyperuricemia) is the underlying cause of gout. Xanthine oxidase is the key enzyme that catalyzes the oxidation of hypoxanthine to xanthine and then to uric acid. Allopurinol, a widely used xanthine oxidase inhibitor is the most commonly used drug to treat gout. However, a small but significant portion of the population suffers from adverse effects of allopurinol that includes gastrointestinal upset, skin rashes and hypersensitivity reactions. Moreover, an elevated level of uric acid is considered as an independent risk factor for cardiovascular diseases. Therefore use of allopurinol-like drugs with minimum side effects is the ideal drug of choice against gout. In this study, we report the synthesis of a series of pyrimidin-5-one analogues as effective and a new class of xanthine oxidase inhibitors. All the synthesized pyrimidin-5-one analogues are characterized by spectroscopic techniques and elemental analysis. Four (6a, 6b, 6d and 6f) out of 20 synthesized molecules in this class showed good inhibition against three different sources of xanthine oxidase, which were more potent than allopurinol based on their respective IC(50) values. Molecular modeling and docking studies revealed that the molecule 6a has very good interactions with the Molybdenum-Oxygen-Sulfur (MOS) complex a key component in xanthine oxidase. These results highlight the identification of a new class of xanthine oxidase inhibitors that have potential to be more efficacious, than allopurinol, to treat gout and possibly against cardiovascular diseases.