Design, synthesis and biological evaluation of 1-alkyl-5/6-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)-1H-indole-3-carbonitriles as novel xanthine oxidase inhibitors

Heterocyclic compounds as xanthine oxidase inhibitors for the management of hyperuricemia: synthetic strategies, structure-activity relationship and molecular docking studies (2018-2024)

Hyperuricemia is characterized by higher-than-normal levels of uric acid in the bloodstream. This condition can increase the likelihood of developing gout, a form of arthritis triggered by the deposition of urate crystals in the joints, leading to inflammation and pain. An essential part of purine metabolism is played by the enzyme xanthine oxidase (XO), which transforms xanthine and hypoxanthine into uric acid. Despite its vital role, diseases such as gout have been associated with elevated uric acid levels, which are linked to increased XO activity. To manage hyperuricemia, this study focuses on potential nitrogen based heterocyclic compounds that may serve as XO inhibitors which may lower uric acid levels and prevent hyperuricemia. Xanthine oxidase inhibitors are a class of medications used to treat conditions like gout by reducing the production of uric acid. The present study demonstrates numerous compounds, particularly nitrogen containing heterocyclic compounds including their synthesis, structure-activity relationship, and molecular docking studies. This paper also contains drugs undergoing clinical studies and the xanthine oxidase inhibitors that have been approved by the FDA.

Design, synthesis, and biological evaluation of 5-(1H-indol-5-yl)isoxazole-3-carboxylic acids as novel xanthine oxidase inhibitors

Xanthine oxidase (XO) is a key enzyme for the production of uric acid in the human body. XO inhibitors (XOIs) are clinically used for the treatment of hyperuricemia and gout, as they can effectively inhibit the production of uric acid. Previous studies indicated that both indole and isoxazole derivatives have good inhibitory effects against XO. Here, we designed and synthesized a novel series of N-5-(1H-indol-5-yl)isoxazole-3-carboxylic acids according to bioisosteric replacement and hybridization strategies. Among the obtained target compounds, compound 6c showed the best inhibitory activity against XO with an IC50 value of 0.13 μM, which was 22-fold higher than that of the classical antigout drug allopurinol (IC50 = 2.93 μM). Structure-activity relationship analysis indicated that the hydrophobic group on the nitrogen atom of the indole ring is essential for the inhibitory potencies of target compounds against XO. Enzyme kinetic studies proved that compound 6c acted as a mixed-type XOI. Molecular docking studies showed that the target compound 6c could not only retain the key interactions similar to febuxostat at the XO binding site but also generate some new interactions, such as two hydrogen bonds between the oxygen atom of the isoxazole ring and the amino acid residues Ser876 and Thr1010. These results indicated that 5-(1H-indol-5-yl)isoxazole-3-carboxylic acid might be an efficacious scaffold for designing novel XOIs and compound 6c has the potential to be used as a lead for further the development of novel anti-gout candidates.

Past, present and future of xanthine oxidase inhibitors: design strategies, structural and pharmacological insights, patents and clinical trials

Xanthine oxidase, a molybdo-flavoenzyme, and an isoform of xanthine dehydrogenase both exist as xanthine oxidoreductase and are responsible for purine catabolism. Xanthine oxidase is more involved in pathological conditions when extensively modulated. Elevation of xanthine oxidase is not only the prime cause of gout but is also responsible for various hyperuricemia associated pathological conditions like diabetes, chronic wounds, cardiovascular disorders, Alzheimer's disease, etc. Currently available xanthine oxidase inhibitors in clinical practice (allopurinol, febuxostat and topiroxostat) suffer from fatal side effects that pose a serious problem to the healthcare system, raising global emergency to develop novel, potent and safer xanthine oxidase inhibitors. This review will provide key and systematic information about: a. design strategies (inspired from both marketed drugs in clinical practice and natural products), structural insights and pharmacological output (xanthine oxidase inhibition and associated activities) of various pre-clinical candidates reported by various research groups across the globe in the past two decades; b. patented xanthine oxidase inhibitors published in the last three decades and c. clinical trials and their outcomes on approved drug candidates. Information generated in this review has suggested fragment-based drug design (FBDD) and molecular hybridization techniques to be most suitable for development of desired xanthine oxidase inhibitors as one provides high selectivity toward the enzyme and the other imparts multifunctional properties to the structure and both may possess capabilities to surpass the limitations of currently available clinical drugs. All in combination will exclusively update researchers working on xanthine oxidase inhibitors and allied areas and potentially help in designing rational, novel, potent and safer xanthine oxidase inhibitors that can effectively tackle xanthine oxidase related disease conditions and disorders.

Agents for the Treatment of Gout: Current Advances and Future Perspectives

Gout is characterized by hyperuricemia and the deposition of monosodium urate (MSU) crystals around joints. Despite the availability of several drugs on the market, its treatment remains challenging owing to the notable side effects, such as hepatorenal toxicity and cardiovascular complications, that are associated with most existing agents. This perspective aims to summarize the current research progress in the development of antigout agents, particularly focusing on xanthine oxidase (XO) and urate anion transporter 1 (URAT1) inhibitors from a medicinal chemistry viewpoint and their preliminary structure-activity relationships (SARs). This perspective provides valuable insights and theoretical guidance to medicinal chemists for the discovery of antigout agents with novel chemical structures, better efficiency, and lower toxicity.

Therapeutic voyage of synthetic and natural xanthine oxidase inhibitors

Xanthine oxidase (XO) inhibitors are commonly used to treat gout, nephropathy, and renal stone diseases related to hyperuricemia. However, recent research has shown that these inhibitors may also have potential benefits in preventing vascular diseases, including those affecting the cerebrovasculature. This is due to emerging evidence suggesting that serum uric acid is involved in the growth of cardiovascular disease, and XO inhibition can reduce oxidative stress in the vasculature. There is a great interest in the development of new XO inhibitors for the treatment of hyperuricemia and gout. The present review discusses the many synthetic and natural XO inhibitors that have been developed which are found to have greater potency.

Identification of 5-[5-cyano-1-(pyridin-2-ylmethyl)-1H-indole-3-carboxamido] thiazole-4-carboxylic acid as a promising dual inhibitor of urate transporter 1 and xanthine oxidase

In combination with allopurinol, tranilast is used as an urate transporter 1 (URAT1) inhibitor for the treatment of hyperuricemia, but its structure-activity relationship concerning URAT1 inhibitory activity is rarely studied. In this paper, analogs 1-30 were designed and synthesized using scaffold hopping strategy on the basis of tranilast and the privileged scaffold indole. Then, URAT1 activity was evaluated using ¹⁴C-uric acid uptake assay with HEK293-URAT1 overexpressing cells. Compared with tranilast (inhibitory rate = 44.9% at 10 μM), most compounds displayed apparent inhibitory effects, ranging from 40.0% to 81.0% at 10 μM on URAT1. Surprisingly, along with the bringing in of a cyano group at the 5-position of indole ring, compounds 26 and 28-30 exerted xanthine oxidase (XO) inhibitory activity. In particular, compound 29 presented potency on URAT1 (48.0% at 10 μM) and XO (IC₅₀ = 1.01 μM). Molecular simulation analysis revealed that the basic structure of compound 29 had an affinity with URAT1, and XO. Furthermore, compound 29 demonstrated a significant hypouricemic effect in a potassium oxonate-induced hyperuricemia rat model at an oral dose of 10 mg/kg during in vivo tests. In summary, tranilast analog 29 was identified as a potent dual-target inhibitor of URAT1 and XO, and a promising lead compound for further investigation.

A consensual machine-learning-assisted QSAR model for effective bioactivity prediction of xanthine oxidase inhibitors using molecular fingerprints

Xanthine oxidase inhibitors (XOIs) have been widely studied due to the promising potential as safe and effective therapeutics in hyperuricemia and gout. Currently, available XOI molecules have been developed from different experiments but they are with the wide structure diversity and significant varying bioactivities. So it is of great practical significance to present a consensual QSAR model for effective bioactivity prediction of XOIs based on a systematic compiling of these XOIs across different experiments. In this work, 249 XOIs belonging to 16 scaffolds were collected and were integrated into a consensual dataset by introducing the concept of IC₅₀ values relative to allopurinol (RIC₅₀). Here, extended connectivity fingerprints (ECFPs) were employed to represent XOI molecules. By performing effective feature selection by machine-learning method, 54 crucial fingerprints were indicated to be valuable for predicting the inhibitory potency (IP) of XOIs. The optimal predictor yields the promising performance by different cross-validation tests. Besides, an external validation of 43 XOIs and a case study on febuxostat also provide satisfactory results, indicating the powerful generalization of our predictor. Here, the predictor was interpreted by shapely additive explanation (SHAP) method which revealed several important substructures by mapping the featured fingerprints to molecular structures. Then, 15 new molecules were designed and predicted by our predictor to show superior IP than febuxostat. Finally, molecular docking simulation was performed to gain a deep insight into molecular binding mode with xanthine oxidase (XO) enzyme, showing that molecules with selenazole moiety, cyano group and isopropyl group tended to yield higher IP. The absorption, distribution, metabolism, excretion and toxicity (ADMET) prediction results further enhanced the potential of these novel XOIs as drug candidates. Overall, this work presents a QSAR model for accurate prediction of IP of XOIs, and is expected to provide new insights for further structure-guided design of novel XOIs.

Design, synthesis and structure-activity relationship of N-phenyl aromatic amide derivatives as novel xanthine oxidase inhibitors

Our previous studies suggested that N-phenyl aromatic amides are a class of promising xanthine oxidase (XO) inhibitor chemotypes. In this effort, several series of N-phenyl aromatic amide derivatives (4a-h, 5-9, 12i-w, 13n, 13o, 13r, 13s, 13t and 13u) were designed and synthesized to carry out an extensive structure-activity relationship (SAR). The investigation provided some valuable SAR information and identified N-(3-(1H-imidazol-1-yl)-4-((2-methylbenzyl)oxy)phenyl)-1H-imidazole-4-carboxamide (12r, IC₅₀ = 0.028 µM) as the most potent XO inhibitor with close in vitro potency to that of topiroxostat (IC₅₀ = 0.017 µM). Molecular docking and molecular dynamics simulation rationalized the binding affinity through a series of strong interactions with the residues Glu1261, Asn768, Thr1010, Arg880, Glu802, etc. In vivo hypouricemic studies also suggested that the uric acid lowering effect of compound 12r was improved compared with the lead g25 (30.61 % vs 22.4 % reduction in uric acid levels at 1 h; 25.91 % vs 21.7 % reduction in AUC of uric acid) . Pharmacokinetic studies revealed that compound 12r presented a short t_1/2 of 0.25 h after oral administration. In addition, 12r has non-cytotoxicity against normal cell HK-2. This work may provide some insights for further development of novel amide-based XO inhibitors.

Chalcone derivatives as xanthine oxidase inhibitors: synthesis, binding mode investigation, biological evaluation, and ADMET prediction

Xanthine oxidase (XO) is a crucial target for the treatment of hyperuricemia and gout. A series of derivatives based on natural 3,4-dihydroxychalcone, obtained from Carthamus tinctorious and Licorice, were designed and synthesized. Nine derivatives (9a-e, 10b,c, and 15a,b) exhibited apparent XO inhibitory activity in vitro (IC₅₀ values varied from 0.121 to 7.086 μM), 15b presented the most potent inhibitory activity (IC₅₀ = 0.121 µM), which was 27.47-fold higher than that of allopurinol (IC₅₀ = 3.324 µM). The SAR analysis indicated that introducing hydroxyl groups at 3'/4'/5'-position on ring A was more beneficial to the inhibition of XO than at 2'/6'-position; the removal of 3‑hydroxyl group on ring B could weaken the inhibitory potency of hydroxychalcones on XO, but it was beneficial to the XO inhibitory potency of methoxychalcones. Molecule modeling studies afforded insights into the binding mode of 15b with XO and supported the findings of SAR analysis. Additionally, kinetics studies demonstrated that 15b presented a reversible and competitive XO inhibitor, which spontaneously combined with XO through hydrophobic force, and finally changed the secondary conformation of XO. Furthermore, the acute hyperuricemia model was employed to investigate the hypouricemic effect of 15b, which could effectively reduce the serum uric acid levels of rats at an oral dose of 10 mg/kg. ADMET prediction suggested that compound 15b possessed good pharmacokinetic properties. Briefly, compound 15b emerges as an interesting XO inhibitor for the treatment of hyperuricemia and gout with beneficial effects on serum uric acid levels regulating. Meanwhile, the XO inhibitors with chalcone skeleton will deserve further attention and discussion.

Research progress on the synthesis and pharmacology of 1,3,4-oxadiazole and 1,2,4-oxadiazole derivatives: a mini review

Oxadiazole is a five-membered heterocyclic compound containing two nitrogen atoms and one oxygen atom. The 1,3,4-oxadiazole and 1,2,4-oxadiazole have favourable physical, chemical, and pharmacokinetic properties, which significantly increase their pharmacological activity via hydrogen bond interactions with biomacromolecules. In recent years, oxadiazole has been demonstrated to be the biologically active unit in a number of compounds. Oxadiazole derivatives exhibit antibacterial, anti-inflammatory, anti-tuberculous, anti-fungal, anti-diabetic and anticancer activities. In this paper, we report a series of compounds containing oxadiazole rings that have been published in the last three years only (2020–2022) as there was no report or their activities described in any article in 2019, which will be useful to scientists in research fields of organic synthesis, medicinal chemistry, and pharmacology.

Synthetic heterocyclic derivatives as promising xanthine oxidase inhibitors: An overview

Inhibition of xanthine oxidase is an effective and most prominent therapeutic approach for the management of gout. Discovery of its association in the pathophysiology of diabetes, cardiovascular disorders, etc., widened its therapeutic horizons. Limited drug candidates in clinical practice along with side effects forced researchers to develop more efficacious and safer xanthine oxidase inhibitors for the management of gout and other disorders associated with xanthine oxidase hyperactivity. In this regard, this review focus on: (a) Various drug candidates in clinical practice and under clinical trials, (b) Development of various heterocyclic motifs as xanthine oxidase inhibitors in last two decades and (c) Various patented synthetic xanthine oxidase inhibitors.

Design, synthesis and biological evaluation of N-(4-alkoxy-3-(1H-tetrazol-1-yl)phenyl) heterocyclic aromatic amide derivatives as xanthine oxidase inhibitors

Xanthine oxidase (XO) is a flavoprotein that exists in various organisms and can catalyze the uric acid formation in the human body. Based on the amide framework of N-(4-((3-cyanobenzyl)oxy)-3-(1H-tetrazol-1-yl)phenyl)isonicotinamide (compound 1) reported in our previous work, a series of N-(4-alkoxy-3-(1H-tetrazol-1-yl)phenyl) heterocyclic aromatic amide derivatives were designed, synthesized and evaluated as novel amide-based XO inhibitors. Structure-activity relationship campaign identified the most promising compound g25 (IC₅₀ = 0.022 μM), which possesses a special 1H-imidazole-5-carboxamide scaffold and presented comparable XO inhibitory potency to topiroxostat (IC₅₀ = 0.017 μM). Enzyme kinetic studies revealed that compound g25 acted as a mixed-type XO inhibitor. Molecular docking and molecular dynamics indicated that imidazole NH of g25 formed two stable hydrogen bonds with Glu1261 residue of XO that provided a vital contribution for the binding affinity. In addition, in vivo activity evaluation demonstrated that compound g25 exhibited obviously hypouricemic effect on a potassium oxonate induced hyperuricemic rat model.

Synthesis and biological evaluation of thiazolidine-2-thione derivatives as novel xanthine oxidase inhibitors

Xanthine oxidase (XO) is a key enzyme in the generation and development of hyperuricemia. Thiazolidine-2-thione, a typical heterocyclic compound, have been widely used in the field of drug synthesis. In this study, a series of novel thiazolidine-2-thione derivatives were synthesized as XO inhibitors, and the XO inhibitory potencies of obtained compounds were evaluated by in vitro enzyme catalysis. The result shown that compound 6k behaved the strongest XO inhibitory activity with an IC₅₀ value of 3.56 μmol/L, which was approximately 2.5-fold more potent than allopurinol. The structure-activity relationship revealed that the phenyl-sulfonamide group was indispensable for thiazolidine-2-thione derivatives to produce XO inhibitory activity. The enzyme inhibition kinetics analyses confirmed that compound 6k exerted a mixed-type XO inhibition. Additionally, the molecular docking results suggested that the 4-fluorophenyl-sulfonyl moiety could interact with Gly260 and Ile264 in the innermost part of the active pocket through 2 hydrogen bonds, while the thiazolidinethione moiety could form two hydrogen bonds with Glu263 and Ser347 in hydrophobic pockets. In summary, the results described above suggested that compound 6k could be a valuable lead compound for the treatment of hyperuricemia as a novel XO inhibitor.

Design, synthesis, and biological evaluation of N-(3-cyano-1H-indol-5/6-yl)-6-oxo-1,6-dihydropyrimidine-4-carboxamides and 5-(6-oxo-1,6-dihydropyrimidin-2-yl)-1H-indole-3-carbonitriles as novel xanthine oxidase inhibitors

Xanthine oxidase (XO) has been an important target for the treatment of hyperuricemia and gout. The analysis of potential interactions of pyrimidinone and 3-cyano indole pharmacophores present in the corresponding reported XO inhibitors with parts of the XO active pocket indicated that they both can be used as effective fragments for the fragment-based design of nonpurine XO inhibitors. In this paper, we adopted the fragment-based drug design strategy to link the two fragments with an amide bond to design the type 1 compounds 13a-13w,14c, 14d, 14f, 14g, 14j, 14k, and 15g. Compound 13g displayed an evident XO inhibitory potency (IC₅₀ = 0.16 μM), which was 52.3-fold higher than that of allopurinol (IC₅₀ = 8.37 μM). For comparison, type 2 compounds 5-(6-oxo-1,6-dihydropyrimidin-2-yl)-1H-indole-3-carbonitriles (25c-25g) were also designed by linking the two fragments with a single bond directly. The results showed that compound 25c from the latter series displayed the best inhibitory potency (IC₅₀ = 0.085 μM), and it was 98.5-fold stronger than that of allopurinol (IC₅₀ = 8.37 μM). These results suggested that amide and single bonds were applicable for linking the two fragments together to obtain potent nonpurine XO inhibitors. The structure-activity relationship results revealed that hydrophobic groups at N-atom of the indole moiety were indispensable for the improvement of the inhibitory potency in vitro against XO. In addition, enzyme kinetics studies suggested that compounds 13g and 25c, as the most promising XO inhibitors for the two types of target compounds, acted as mixed-type inhibitors for XO. Moreover, molecular modeling studies suggested that the pyrimidinone and indole moieties of the target compounds could interact well with key amino acid residues in the active pocket of XO. Furthermore, in vivo hypouricemic effect demonstrated that compounds 13g and 25c could effectively reduce serum uric acid levels at an oral dose of 10 mg/kg. Therefore, compounds 13g and 25c could be potential and efficacious agents for the treatment of hyperuricemia and gout.

Amide-based xanthine oxidase inhibitors bearing an N-(1-alkyl-3-cyano-1H-indol-5-yl) moiety: Design, synthesis and structure-activity relationship investigation

Our previous work identified a promising isonicotinamide based xanthine oxidase (XO) inhibitor, N-(3-cyano-4-((2-cyanobenzyl)oxy)phenyl)isonicotinamide (1), and concluded that amide is an effective linker in exploring the XO inhibitor chemical space that is completely different from the five-membered ring framework of febuxostat and topiroxostat. Indole, an endogenous bioactive substance and a popular drug construction fragment, was involved in the structural optimization campaign of the present effort. After the installation of some functional groups, N-(1-alkyl-3-cyano-1H-indol-5-yl) was generated and employed to mend the missing H-bond interaction between the 3'-cyano of 1 and Asn768 residue of XO by shortening their distance. In this context, eight kinds of heterocyclic aromatic amide chemotypes were rationally designed and synthesized to investigate the structure-activity relationship (SAR) of amide-based XO inhibitors. The optimized compound a6 (IC₅₀ = 0.018 μM) exhibits 17.2-fold improved potency than the initial compound 1 (IC₅₀ = 0.31 μM). Its potency is comparable to that of topiroxostat (IC₅₀ = 0.013 μM). Molecular docking and molecular dynamics studies proved the existence of the stable H-bond between the cyano group and the Asn768 residue. Moreover, oral administration of a6 (11.8 mg/kg) could effectively reduce serum uric acid levels in an acute hyperuricemia rat model. Liver microsomal stability assay illustrated that compound a6 possesses well metabolic stability in rat liver microsomes. However, the in vivo potency of a6 was much lower than that of topiroxostat, which may be explained by the poor absorption found in the parallel artificial membrane permeability assay (PAMPA). In addition, 6a has non-cytotoxicity against normal cell lines MCF10A and 16HBE. Taken together, this work culminated in the identification of compound 6a as an excellent lead for further exploration of amide-based XO inhibitors.

Design, synthesis and bioactive evaluation of geniposide derivatives for antihyperuricemic and nephroprotective effects

Hyperuricemia is a principal factor mediating gout and kidney damage, and xanthine oxidase (XOD) is a key enzyme in the pathogenesis of hyperuricemia. In this context, a series of geniposide derivatives were designed and synthesized, and antihyperuricemic and nephroprotective effects of all derivatives was evaluated in vitro and in vivo. Compound 2e emerged as the most potent XOD inhibitor, with an IC₅₀ value of 6.67 ± 0.46 µM. Simultaneously, cell viability, ROS generation, and SOD levels assay showed that compound 2e could repair the damage of HKC cells by inhibiting the oxidative stress response. The results of the study indicated compound 2e significantly decreased uric acid levels by inhibiting the XOD activity, and repaired kidney damage by inhibiting the expression of TLR4/TLR2/MyD88/NF-κB and NALP3/ASC/caspase-1 signaling pathways. Enzyme inhibition kinetics suggested that compound 2e functioned via reversible mixed competitive inhibition. Moreover, a molecular docking study was performed to gain insight into the binding mode of compound 2e with XOD. These results suggest that geniposide derivatives were potential to be developed into a novel medicine to reveal healthy benefits in natural prevention and reduction risk of hyperuricemia and kidney damage.

Febuxostat-based amides and some derived heterocycles targeting xanthine oxidase and COX inhibition. Synthesis, in vitro and in vivo biological evaluation, molecular modeling and in silico ADMET studies

Various febuxostat derivatives comprising carboxamide functionalities and different substituted heterocycles were synthesized and evaluated for their biological activities as xanthine oxidase (XO) and cyclooxygenase (COX) inhibitors. All the tested compounds exhibited variable in vitro XO inhibitory activities (IC₅₀ values 0.009-0.077 µM), among which the analog 17 has emerged as the most potent derivative (IC₅₀ 0.009 µM), representing nearly 3-times the potency of febuxostat (IC₅₀ 0.026 µM). The same analogs were further investigated for their in vitro COX-1 and COX-2 inhibitory activity, where fifteen analogs demonstrated recognizable COX-2 inhibitory potential (IC₅₀ values range 0.04 - 0.1 µM), when correlated with celecoxib (IC₅₀ 0.05 µM), together with appreciable selectivity indices. Compounds 5a, 14b, 17, 19c, 19e and 21b that showed significant in vitro XO and/ or COX inhibitory potentials were further investigated for their in vivo hypouricemic as well as anti-inflammatory activities. Interestingly, the in vivo results were concordant with the collected in vitro data. Docking of compounds 5a, 14b, 17, 19c, 19e and 21b with the active sites of XO and COX-2 isozymes demonstrated superior binding profile compared with the reported ligands (febuxostat and celecoxib, respectively). Their docking scores were reasonable and cohering to a great extent with their corresponding in vitro IC₅₀ values. Moreover, in silico computation of the predicted pharmacokinetic and toxicity properties (ADMET), together with the ligand efficiency (LE) of the same six compounds suggesting their liability to act as new orally active drug candidates with a predicted high safety profile.

Synthesis and biological evaluation of 2-(4-alkoxy-3-cyano)phenylpyrimidine derivatives with 4-amino or 4-hydroxy as a pharmacophore element binding with xanthine oxidase active site

Xanthine oxidase is the rate-limiting enzyme critical for the synthesis of uric acid, and therefore xanthine oxidase inhibitors are considered as one of the promising therapies for hyperuricemia and gout. In our previous study, series of 2-(4-alkoxy-3-cyano)phenyl-6-oxo-1,6-dihydropyrimidine-5-carboxylic acids and 2-(4-alkoxy-3-cyano)phenyl-6-imino-1,6-dihydropyrimidine-5-carboxylic acids were synthesized that presented excellent in vitro xanthine oxidase inhibitory potency. Interestingly, molecular docking studies revealed that the interaction behavior of these compounds with xanthine oxidase was changed after the conversion from a hydroxy group to amine group. To further investigate the structure-activity relationships of these pyrimidine-containing xanthine oxidase inhibitors and explore the contribution of amino or hydroxy group on xanthine oxidase inhibitory potency, several 2-phenylpyrimidine derivatives with amino or hydroxy functional group were designed and synthesized. Thereafter, the structure-activity research and molecular modeling study proved that hydroxy and amino groups could be used as pharmacophore elements for the design of 2-phenylpyrimidines xanthine oxidase inhibitors. Particularly, the optimized compound, 2-(3-cyano-4-isopentoxy)phenylpyrimidine-4-ol, emerged the strongest xanthine oxidase inhibitor potency, with an IC₅₀ value of 0.046 µM, which was approximately 120-fold more potent than that of allopurinol (IC₅₀ = 5.462 µM). Additionally, Lineweaver-Burk plot analysis revealed that the optimized compound acted as a mixed-type inhibitor. Furthermore, the in vivo hypouricemic effect of the optimized compound was investigated in a hyperuricemia rat model induced by potassium oxonate, and the results showed that the optimized compound could effectively reduce serum uric acid levels at an oral dose of 30 mg/kg.