Targeting bacterial nickel transport with aspergillomarasmine A suppresses virulence-associated Ni-dependent enzymes.

Microbial Ni2+ homeostasis underpins the virulence of several clinical pathogens. Ni2+ is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization and persistence. Many microbes produce metallophores to sequester metals necessary for their metabolism and starve competing neighboring organisms. The fungal metallophore aspergillomarasmine A (AMA) shows narrow specificity for Zn2+, Ni2+, and Co2+. Here, we show that this specificity allows AMA to block the uptake of Ni2+ and attenuate bacterial Ni-dependent enzymes, offering a potential strategy for reducing virulence. Bacterial exposure to AMA perturbs H2 metabolism, ureolysis, struvite crystallization, and biofilm formation and shows efficacy in a Galleria mellonella animal infection model. The inhibition of Ni-dependent enzymes was aided by Zn2+, which complexes with AMA and competes with the native nickelophore for the uptake of Ni2+. Biochemical analyses demonstrated high-affinity binding of AMA-metal complexes to NikA, the periplasmic substrate-binding protein of the Ni2+ uptake system. Structural examination of NikA in complex with Ni-AMA revealed that the coordination geometry of Ni-AMA mimics the native ligand, Ni-(L-His)2, providing a structural basis for binding AMA-metal complexes. Structure-activity relationship studies of AMA identified regions of the molecule that improve NikA affinity and offer potential routes for further developing this compound as an anti-virulence agent.

Machine Learning-Driven Classification of Urease Inhibitors Leveraging Physicochemical Properties as Effective Filter Criteria.

Urease, a pivotal enzyme in nitrogen metabolism, plays a crucial role in various microorganisms, including the pathogenic Helicobacter pylori. Inhibiting urease activity offers a promising approach to combating infections and associated ailments, such as chronic kidney diseases and gastric cancer. However, identifying potent urease inhibitors remains challenging due to resistance issues that hinder traditional approaches. Recently, machine learning (ML)-based models have demonstrated the ability to predict the bioactivity of molecules rapidly and effectively. In this study, we present ML models designed to predict urease inhibitors by leveraging essential physicochemical properties. The methodological approach involved constructing a dataset of urease inhibitors through an extensive literature search. Subsequently, these inhibitors were characterized based on physicochemical properties calculations. An exploratory data analysis was then conducted to identify and analyze critical features. Ultimately, 252 classification models were trained, utilizing a combination of seven ML algorithms, three attribute selection methods, and six different strategies for categorizing inhibitory activity. The investigation unveiled discernible trends distinguishing urease inhibitors from non-inhibitors. This differentiation enabled the identification of essential features that are crucial for precise classification. Through a comprehensive comparison of ML algorithms, tree-based methods like random forest, decision tree, and XGBoost exhibited superior performance. Additionally, incorporating the "chemical family type" attribute significantly enhanced model accuracy. Strategies involving a gray-zone categorization demonstrated marked improvements in predictive precision. This research underscores the transformative potential of ML in predicting urease inhibitors. The meticulous methodology outlined herein offers actionable insights for developing robust predictive models within biochemical systems.

Design and synthesis of new N-thioacylated ciprofloxacin derivatives as urease inhibitors with potential antibacterial activity.

A new series of N-thioacylated ciprofloxacin 3a-n were designed and synthesized based on Willgerodt-Kindler reaction. The results of in vitro urease inhibitory assay indicated that almost all the synthesized compounds 3a-n (IC50 = 2.05 ± 0.03-32.49 ± 0.32 µM) were more potent than standard inhibitors, hydroxyurea (IC50 = 100 ± 2.5 µM) and thiourea (IC50 = 23 ± 0.84 µM). The study of antibacterial activity against Gram-positive species (S. aureus and S. epidermidis) revealed that the majority of compounds were more active than ciprofloxacin as the standard drug, and 3h derivative bearing 3-fluoro group had the same effect as ciprofloxacin against Gram-negative bacteria (P. aeruginosa and E. coli). Based on molecular dynamic simulations, compound 3n exhibited pronounced interactions with the critical residues of the urease active site and mobile flap pocket so that the quinolone ring coordinated toward the metal bi-nickel center and the essential residues at the flap site like His593, His594, and Arg609. These interactions caused blocking the active site and stabilized the movement of the mobile flap at the entrance of the active site channel, which significantly reduced the catalytic activity of urease. Noteworthy, 3n also exhibited IC50 values of 5.59 ± 2.38 and 5.72 ± 1.312 µg/ml to inhibit urease enzyme against C. neoformans and P. vulgaris in the ureolytic assay.

Synthesis and evaluation of novel 1, 2, 4-substituted triazoles for urease and anti-proliferative activity.

1,2,4-triazoles are a major group of heterocyclic compounds. In the current work, a concise library of such triazoles synthesized through a multistep protocol. The synthesis involved hydrazinolysis of ethyl-2-(p-Cl-phenoxy) acetate followed by reflux with phenyl isothiocyanate to yield the intermediate 2-[2-(p-Cl-phenoxy)acetyl)-N-phenyl-hydrazinecarbothioamide. This intermediate was then cyclized to form 5-[p-(Cl-phenoxy)-methyl]-4-phenyl-4H-1,2,4-triazole-3-thiol (the parent moiety) at alkaline pH. In parallel, 3-bromopropionyl bromide was reacted with a series of phenylamines to yield N-(substituted-phenyl)bromopropanamides. In the final step, N-substitution of 5-[p-(Cl-phenoxy)-methyl]-4- phenyl-4H-1,2,4-triazole-3-thiol was carried out with N-(substituted-phenyl)bromopropanamides to give desired library of 3-[5-[(p-Cl-phenoxy)-methyl]-4- phenyl-4H-1,2,4-triazole-3-ylthio]-N-(substituted-phenyl) propan-amides (8a-l). The prepared moieties were identified via IR, NMR, & EIMS and evaluated for urease and anti-proliferative activities. 3-[5-[(p-Cl-phenoxy)-methyl]-4- phenyl-4H-1,2,4-triazole-3-ylthio]-N-(3-methyl-phenyl)propanamide 8k, was found to be most prominent hit as urease inhibitor (IC50= 42.57± 0.13 µM) using thiourea as standard (IC50= 21.25±0.15µM). The interaction of 8k with urease were studied using docking studies. Anti-proliferative activity results showed 8k as promising candidates and rest of the synthesized derivatives were found to be moderately anti-proliferative. Molecular docking results also displayed 8k, 8h, and 8c as potential hits for further study.

Urease inhibition and DPPH radical scavenging potential of phytoconstituent from Alstonia scholaris and molecular docking interactions of bioactive luteolin with target proteins.

A polyphenolic flavone Luteolin (3',4',5,7-tetrahydroxyflavone) is found in various plants and is traditionally used in Chinese medicine. It is obtained from Alstonia scholaris (L.) R.Br Flower belonging to the family Apocynaceae while investigation. Various studies have been demonstrated the antioxidant or antiulcer potential of luteolin from different plant sources. In the present investigation the antioxidant or antiulcer effect of the Luteolin has been carried out using molecular docking simulations. The objective of this study was to analyze the antioxidant and antiulcer potential of luteolin obtained during isolation. The in vitro biological evaluation has been supported by the in silico studies using Autodock vina 4 shows the ligand-protein interaction of lute olin with 1HD2, 4GY7 and 3O1Q. Luteolin showed significant DPPH scavenging and urease inhibition activity i.e., 23.4 ± 0.87, 6.21±0.45 IC50 (uM) respectively as compared to the standard BHA and thiourea 44.2±0.45, 22.4±0.29 IC50 (uM) respectively. The docking simulations showed significant binding pocket sites with the respective proteins1HD2, 4GY7 and 3O1Q with the least binding energy -6.8, -8.0 and -8.2 kcal/mol respectively. Thus, Strong evidence has been presented with their confirmation structural interaction via molecular docking with proteins that serve as binding sites for available Luteolin molecule. The findings justify the application of the compound as a novel antioxidant and antiulcer agent.

Design and synthesis of novel nitrothiazolacetamide conjugated to different thioquinazolinone derivatives as anti-urease agents.

The present article describes the design, synthesis, in vitro urease inhibition, and in silico molecular docking studies of a novel series of nitrothiazolacetamide conjugated to different thioquinazolinones. Fourteen nitrothiazolacetamide bearing thioquinazolinones derivatives (8a-n) were synthesized through the reaction of isatoic anhydride with different amine, followed by reaction with carbon disulfide and KOH in ethanol. The intermediates were then converted into final products by treating them with 2-chloro-N-(5-nitrothiazol-2-yl)acetamide in DMF. All derivatives were then characterized through different spectroscopic techniques (1H, 13C-NMR, MS, and FTIR). In vitro screening of these molecules against urease demonstrated the potent urease inhibitory potential of derivatives with IC50 values ranging between 2.22 ± 0.09 and 8.43 ± 0.61 µM when compared with the standard thiourea (IC50 = 22.50 ± 0.44 µM). Compound 8h as the most potent derivative exhibited an uncompetitive inhibition pattern against urease in the kinetic study. The high anti-ureolytic activity of 8h was confirmed against two urease-positive microorganisms. According to molecular docking study, 8h exhibited several hydrophobic interactions with Lys10, Leu11, Met44, Ala47, Ala85, Phe87, and Pro88 residues plus two hydrogen bound interactions with Thr86. According to the in silico assessment, the ADME-Toxicity and drug-likeness profile of synthesized compounds were in the acceptable range.

Expression, Purification, and Comparative Inhibition of Helicobacter pylori Urease by Regio-Selectively Alkylated Benzimidazole 2-Thione Derivatives.

The urease enzyme has been an important target for the discovery of effective pharmacological and agricultural products. Thirteen regio-selectively alkylated benzimidazole-2-thione derivatives have been designed to carry the essential features of urease inhibitors. The urease enzyme was isolated from Helicobacter pylori as a recombinant urease utilizing the His-tag method. The isolated enzyme was purified and characterized using chromatographic and FPLC techniques showing a maximal activity of 200 mg/mL. Additionally, the commercial Jack bean urease was purchased and included in this study for comparative and mechanistic investigations. The designed compounds were synthesized and screened for their inhibitory activity against the two ureases. Compound 2 inhibited H. pylori and Jack bean ureases with IC50 values of 0.11; and 0.26 mM; respectively. While compound 5 showed IC50 values of 0.01; and 0.29 mM; respectively. Compounds 2 and 5 were docked against Helicobacter pylori urease (PDB ID: 1E9Y; resolution: 3.00 Å) and exhibited correct binding modes with free energy (ΔG) values of -9.74 and -13.82 kcal mol-1; respectively. Further; the in silico ADMET and toxicity properties of 2 and 5 indicated their general safeties and likeness to be used as drugs. Finally, the compounds' safety was authenticated by an in vitro cytotoxicity assay against fibroblast cells.

Synthesis, Biological Evaluation and in Silico Studies of New Pyrazoline Derivatives Bearing Benzo[d]thiazol-2(3H)-one Moiety as Potential Urease Inhibitors.

Novel pyrazoline derivatives containing benzo[d]thiazol-2(3H)-one moiety were synthesized and screened for their inhibitory properties against urease, a clinically important metabolic enzyme. In vitro enzyme inhibition studies revealed that all pyrazolines (7.21-87.77 µM) were more potent than the standard inhibitor acetohydroxamic acid (251.74 µM) against the urease enzyme. Most notably, compound 2m, which is more active than the other compounds in vitro and molecular docking studies, showed a significant inhibition potential and efficient IC50 values (7.21±0.09 µM) and in silico inhibition constant (0.11 µM). Furthermore, molecular dynamics (MD) simulation analysis suggests that the binding stability of urease enzyme and compound 2m were stably maintained during the 100 ns simulation time. Compound 2m also exhibited good physicochemical and pharmacokinetic parameters. The overall results of urease inhibition have indicated that these pyrazoline derivative compounds can be further optimized and developed for the discovery of novel urease inhibitors.

Muricazine, a new hydrazine derivative from Ranunculus muricatus L. with antioxidant, lipoxygenase and urease inhibitory activities.

Ranunculus muricatus L., an important member of family Ranunculaceae upon submission to phytochemical studies, led to the isolation of a novel natural hydrazine derivative, muricazine (1). Chemical structure of the compound was established with the aid of advanced spectroscopic techniques. It was evaluated for in vitro antioxidant, lipoxygenase, and urease (jack-bean) inhibitory activities. Results suggested that compound 1 could scavenge the DPPH free radical (42.1 ± 0.12 µM) to a great extent as compared to the standard (40.6 ± 0.91 µM). However, it showed moderate inhibitory potential against lipoxygenase (65.2 ± 0.45 µM) and urease (54.8 ± 0.23 µM) enzymes.

Recent Efforts in the Discovery of Urease Inhibitor Identifications.

Urease is an attractive drug target for designing anti-infective agents against pathogens such as Helicobacter pylori, Proteus mirabilis, and Ureaplasma urealyticum. In the past century, hundreds of medicinal chemists focused their efforts on explorations of urease inhibitors. Despite the FDA's approval of acetohydroxamic acid as a urease inhibitor for the treatment of struvite nephrolithiasis and the widespread use of N-(n-butyl)thiophosphoric triamide as a soil urease inhibitor as nitrogen fertilizer synergists in agriculture, urease inhibitors with high potency and safety are urgently needed. Exploration of novel urease inhibitors has therefore become a hot research topic recently. Herein, inhibitors identified worldwide from 2016 to 2021 have been reviewed. They structurally belong to more than 20 classes of compounds such as urea/thioure analogues, hydroxamic acids, sulfonamides, metal complexes, and triazoles. Some inhibitors showed excellent potency with IC50 values lower than 10 nM, having 10000-fold higher potency than the positive control thiourea.

Monte-Carlo method-based QSAR model to discover phytochemical urease inhibitors using SMILES and GRAPH descriptors.

Urease inhibitors are known to play a vital role in the field of medicine as well as agriculture. Special attention is attributed to the development of novel urease inhibitors with a view to treat the Helicobacter pylori infection. Amongst a number of urease inhibitors, a large number of molecules fail in vivo and in clinical trials due to their hydrolytic instability and toxicity profile. The search for potential inhibitors may require screening of large and diverse databases of small molecules and to design novel molecules. We developed a Monte-Carlo method-based QSAR model to predict urease inhibiting potency of molecules using SMILES and GRAPH descriptors on an existing diverse database of urease inhibitors. The QSAR model satisfies all the statistical parameters required for acceptance as a good model. The model is applied to identify urease inhibitors among the wide range of compounds in the phytochemical database, NPACT, as a test case. We combine the ligand-based and structure-based drug discovery methods to improve the accuracy of the prediction. The method predicts pIC50 and estimates docking score of compounds in the database. The method may be applied to any other database or compounds designed in silico to discover novel drugs targeting urease.Communicated by Ramaswamy H. Sarma.

Synthesis and Biological Evaluation of Dithiobisacetamides as Novel Urease Inhibitors.

Thirty-eight disulfides containing N-arylacetamide were designed and synthesized in an effort to develop novel urease inhibitors. Biological evaluation revealed that some of the synthetic compounds exhibited strong inhibitory potency against both cell-free urease and urease in intact cell with low cytotoxicity to mammalian cells even at concentration up to 250 µM. Of note, 2,2'-dithiobis(N-(2-fluorophenyl)acetamide) (d7), 2,2'-dithiobis(N-(3,5-difluorophenyl)acetamide) (d24), and 2,2'-dithiobis(N-(3-fluorophenyl)acetamide) (d8) were here identified as the most active inhibitors with IC50 of 0.074, 0.44, and 0.81 µM, showing 32- to 355-fold higher potency than the positive control acetohydroxamic acid. These disulfides were confirmed to bind urease without covalent modification of the cysteine residue and to inhibit urease reversibly with a mixed inhibition mechanism. They also showed very good anti-Helicobacter pylori activities with d8 showing a comparable potency to the clinical used drug amoxicillin. The impressive in vitro biological profile indicated their immense potential as therapeutic agents to tackle H. pylori caused infections.

Discovery of urease inhibitory effect of sulfamate derivatives: Biological and computational studies.

The discovery of life-changing medicines continues to be the driving force for the rapid exploration and expansion of chemical space, enabling access to innovative small molecules of medicinal importance. These small molecules remain the backbone for modern drug discovery. In this context, the treatment of ureolytic bacterial infections inspires the identification of potent and effective inhibitors of urease, a promising and highly needed target for H. pylori eradication. The present study explores the evaluation of sulfamate derivatives for the inhibition of urease enzyme. The tested compounds showed remarkable inhibitory effect and high level of potency. Compound 1q emerged as the lead inhibitor with an IC50 value of 0.062 ± 0.001 µM, ∼360-fold more potent than thiourea (IC50 = 22.31 ± 0.031 µM). The assessment of various contributing factors towards the inhibition profile allowed for the establishment of diverse structure-activity relationships. Kinetics studies revealed the competitive mode of inhibition of compound 1q while molecular modeling analysis identified various crucial binding interactions with ARG609, ARG439, HIS519, HIS492, HIS593, ALA440, and ALA636 in the active pocket of the enzyme. Finally, the calculated pharmacokinetic properties suggest a promising profile of our potent sulfamate-based urease inhibitors.

Synthesis, Characterization and Crystal Structures of Schiff Base Copper Complexes with Urease Inhibitory Activity.

Urease inhibitors can inhibit the decomposition rate of urea, and decrease the air pollution caused by ammonia. In this paper, four new copper(II) complexes [CuL(ONO2)]n (1), [Cu2L2(µ1,3-N3)2] (2), [CuBrL] (3), and [CuClL] (4), where L = 5-bromo-2-(((2-methylamino)ethyl)imino)methyl)phenolate, have been synthesized and characterized. The complexes were characterized by elemental analyses, IR and UV-Vis spectroscopy, molar conductivity, and single crystal X-ray diffraction. X-ray analysis reveals that Cu atoms in complexes 1 and 2 are in square pyramidal coordination, and those in complexes 3 and 4 are in square planar coordination. The molecules of the complexes are linked through hydrogen bonds and π···π interactions. The inhibitory effects of the complexes on Jack bean urease were studied, which showed that the complexes have effective activity on urease.

Synthesis, Crystal Structures and Urease Inhibition of 4-Bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide and Its Dinuclear Copper(II) Complex.

A new dinuclear copper(II) complex [Cu2(µ-Br)2L2]·0.5MeOH with the benzohydrazone ligand 4-bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL) has been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopic studies. Single crystal structures of the complex and the benzohydrazone compound were studied. The Cu atoms in the complex are coordinated by two benzohydrazone ligands and two Br bridging groups, forming square pyramidal coordination. The complex has good inhibitory activity on Jack bean urease, with IC50 value of 1.38 µmol·L-1.

Effect of High Hydrostatic Pressure Treatment on Urease Activity and Inhibition of Fishy Smell in Mackerel (Scomber japonicus) during Storage.

In this study, the physicochemical changes related to fishy smell were determined by storing high hydrostatic pressure (HHP)-treated mackerel (Scomber japonicus) meat in a refrigerator for 20 days. The inhibition of crude urease activity from Vibrio parahaemolyticus using HHP treatment was also investigated. The mackerel meat storage experiment demonstrated that production of trimethylamine (TMA) and volatile basic nitrogen (VBN), the main components of fishy smell, was significantly reduced on the 20th day of storage after the HHP treatment compared to the untreated mackerels. The results demonstrated that the increased ammonia nitrogen rates in the 2000, 3000, and 4000 bar, HHP-treated groups decreased by 23.8%, 23.8%, and 31.0%, respectively, compared to the untreated groups. The enzyme activity of crude urease was significantly reduced in the HHP-treated group compared to that in the untreated group. Measurement of the volatile organic compounds (VOCs) in mackerel meat during storage indicated that the content of ethanol, 2-butanone, 3-methylbutanal, and trans-2-pentenal, which are known to cause off-flavor due to spoilage, were significantly reduced by HHP treatment. Collectively, our results suggested that HHP treatment would be useful for inhibiting the activity of urease, thereby reducing the fishy smells from fish and shellfish.

Exploring Amantadine Derivatives as Urease Inhibitors: Molecular Docking and Structure-Activity Relationship (SAR) Studies.

This article describes the design and synthesis of a series of novel amantadine-thiourea conjugates (3a-j) as Jack bean urease inhibitors. The synthesized hybrids were assayed for their in vitro urease inhibition. Accordingly, N-(adamantan-1-ylcarbamothioyl)octanamide (3j) possessing a 7-carbon alkyl chain showed excellent activity with IC50 value 0.0085 ± 0.0011 µM indicating that the long alkyl chain plays a vital role in enzyme inhibition. Whilst N-(adamantan-1-ylcarbamothioyl)-2-chlorobenzamide (3g) possessing a 2-chlorophenyl substitution was the next most efficient compound belonging to the aryl series with IC50 value of 0.0087 ± 0.001 µM. The kinetic mechanism analyzed by Lineweaver-Burk plots revealed the non-competitive mode of inhibition for compound 3j. Moreover, in silico molecular docking against target protein (PDBID 4H9M) indicated that most of the synthesized compounds exhibit good binding affinity with protein. The compound 3j forms two hydrogen bonds with amino acid residue VAL391 having a binding distance of 1.858 Å and 2.240 Å. The interaction of 3j with amino acid residue located outside the catalytic site showed its non-competitive mode of inhibition. Based upon these results, it is anticipated that compound 3j may serve as a lead structure for the design of more potent urease inhibitors.

Synthesis, In Silico Studies, and Evaluation of Syn and Anti Isomers of N-Substituted Indole-3-carbaldehyde Oxime Derivatives as Urease Inhibitors against Helicobacter pylori.

Gastrointestinal tract infection caused by Helicobacter pylori is a common virulent disease found worldwide, and the infection rate is much higher in developing countries than in developed ones. In the pathogenesis of H. pylori in the gastrointestinal tract, the secretion of the urease enzyme plays a major role. Therefore, inhibition of urease is a better approach against H. pylori infection. In the present study, a series of syn and anti isomers of N-substituted indole-3-carbaldehyde oxime derivatives was synthesized via Schiff base reaction of appropriate carbaldehyde derivatives with hydroxylamine hydrochloride. The in vitro urease inhibitory activities of those derivatives were evaluated against that of Macrotyloma uniflorum urease using the modified Berthelot reaction. Out of the tested compounds, compound 8 (IC50 = 0.0516 ± 0.0035 mM) and compound 9 (IC50 = 0.0345 ± 0.0008 mM) were identified as the derivatives with potent urease inhibitory activity with compared to thiourea (IC50 = 0.2387 ± 0.0048 mM). Additionally, in silico studies for all oxime compounds were performed to investigate the binding interactions with the active site of the urease enzyme compared to thiourea. Furthermore, the drug-likeness of the synthesized oxime compounds was also predicted.

High-throughput tandem-microwell assay for ammonia repositions FDA-Approved drugs to inhibit Helicobacter pylori urease.

To date, little attempt has been made to develop new treatments for Helicobacter pylori (H. pylori), although the community is aware of the shortage of treatments for H. pylori. In this study, we developed a 192-tandem-microwell-based high-throughput assay for ammonia that is a known virulence factor of H. pylori and a product of urease. We could identify few drugs, that is, panobinostat, dacinostat, ebselen, captan, and disulfiram, to potently inhibit the activity of ureases from bacterial or plant species. These inhibitors suppress the activity of urease via substrate-competitive or covalent-allosteric mechanism, but all except captan prevent the antibiotic-resistant H. pylori strain from killing human gastric cells, with a more pronounced effect than acetohydroxamic acid, a well-known urease inhibitor and clinically used drug for the treatment of bacterial infection. This study offers several bases for the development of new treatments for urease-containing pathogens and to study the mechanism responsible for the regulation of urease activity.

Soil urease inhibition by various plant extracts.

Urea is the most popular and widely used nitrogenous fertilizer. High soil urease activity rapidly hydrolyses applied urea to ammonia which contributes to soil nitrogen (N) losses and reduces N use efficiency of crop plants. The ammonia losses can be minimized by the inhibition of soil urease activity which has been explored using various potential chemical inhibitors. However, the soil urease activity inhibition potential of plant extracts is rarely explored to date. In the present study, extracts of 35 plant materials were taken and evaluated against jack bean urease. Eleven extracts, showing >50% jack bean urease inhibition, were selected and further investigated in 13 soils collected from various districts of Punjab, Pakistan. Interestingly, except Capsicum annum, Melia azedarach, Citrus reticulata and Quercus infectoria, the plant extracts showed urease inhibition activities in soils, the extent of which was lower as compared to that observed in jack bean urease though. Maximum urea hydrolysis inhibition (70%) was noted with Vachellia nilotica which was 40% more than that of hydroquinone (50%) followed by that of Eucalyptus camaldulensis (24%). The extracts of V. nilotica and E. camaldulensis were coated on urea and applied to soil in the next step. At 21st day, 239% and 116% more urea-N was recovered from soil treated with V. nilotica and E. camaldulensis extracts coated urea, respectively, as compared to uncoated urea. Conclusively, these results indicated that the coating of V. nilotica and E. camaldulensis extracts on urea prills prolonged urea persistence in soil owing to minimum urea hydrolysis, probably, the extracts of V. nilotica and E. camaldulensis showed their urease inhibition potential. The results of this study provide a base line for the identification of new soil urease inhibitor compounds from plant materials in future.