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 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.

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.

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.

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.

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.

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.

Bio-oriented synthesis of new sulphadiazine derivatives for urease inhibition and their pharmacokinetic analysis

Current research is based on biology-oriented synthesis of sulphadiazine derivatives and determination of their urease inhibitory activity. In this regard, a series of (E)-4-(benzylideneamino)-N-(pyrimidin-2-yl)benzenesulfonamide was synthesized from sulphadiazine and substituted aromatic aldehydes. The structures of synthesized compounds were ascertained by spectroscopic techniques, such as, FTIR, NMR and HRMS analysis, and in-vitro and in-silico investigation were carried out for the inhibition of urease. Ureases are harmful for humans by producing by-products of urea (ammonia and carbon dioxide). The most active compound (3l) against urease exhibited IC50 value of 2.21 ± 0.45 µM which is 10 times more potent than the standard thiourea (20.03 ± 2.06 µM). It is noteworthy that most of our synthesized compounds showed significant to excellent activities against urease enzyme and most of them substituted by halogen or hydroxy groups at ortho and para positions in their structures. Inhibition of enzyme by the synthesized analogues was in descending order as 3l > 3a > 3b > 3q > 3e > 3o > 3s > 3t > 3g > 3k > 3r > 3f > 3m > 3p > 3n > 3j > 3i > 3h. Moreover, molecular docking studies were performed to rationalize the binding interactions of the synthesized motifs with the active pocket of the urease enzyme. The synthesized sulphadiazine derivatives (3a-u) were found to be non-toxic, and presented passive gastrointestinal absorption.

Zerumbone Inhibits Helicobacter pylori Urease Activity

Helicobacter pylori (H. pylori) produces urease in order to improve its settlement and growth in the human gastric epithelium. Urease inhibitors likely represent potentially powerful therapeutics for treating H. pylori; however, their instability and toxicity have proven problematic in human clinical trials. In this study, we investigate the ability of a natural compound extracted from Zingiber zerumbet Smith, zerumbone, to inhibit the urease activity of H. pylori by formation of urease dimers, trimers, or tetramers. As an oxygen atom possesses stronger electronegativity than the first carbon atom bonded to it, in the zerumbone structure, the neighboring second carbon atom shows a relatively negative charge (δ⁻) and the next carbon atom shows a positive charge (δ⁺), sequentially. Due to this electrical gradient, it is possible that H. pylori urease with its negative charges (such as thiol radicals) might bind to the β-position carbon of zerumbone. Our results show that zerumbone dimerized, trimerized, or tetramerized with both H. pylori urease A and urease B molecules, and that this formation of complex inhibited H. pylori urease activity. Although zerumbone did not affect either gene transcription or the protein expression of urease A and urease B, our study demonstrated that zerumbone could effectively dimerize with both urease molecules and caused significant functional inhibition of urease activity. In short, our findings suggest that zerumbone may be an effective H. pylori urease inhibitor that may be suitable for therapeutic use in humans.

Therapeutic potential of N4-substituted thiosemicarbazones as new urease inhibitors: Biochemical and in silico approach

Urease enzyme plays a key role in pathogenesis of gastritis and peptic ulcers. Its inhibition averts our bodies from many disorders including formation of urinary calculi. In agriculture, the high urease content causes severe environmental and hence economic problems. Due to deficiency of effective and safer drugs to tackle the aforementioned disorders, the quest for new scaffolds becomes mandatory in the field of medicinal chemistry. In this regard, we herein report a new series of N⁴-substituted thiosemicarbazones 3a-v as potential candidates for urease inhibition. These new N⁴-substituted thiosemicarbazones 3a-v of distant chemical scaffolds were characterized by advanced spectroscopic techniques, such as FTIR, ¹HNMR, ¹³CNMR, ESI-MS and in the case of compound 3g by single crystal X-ray analysis. The compounds were evaluated for their urease inhibitory potential. All newly synthesized compounds showed significant urease inhibitions with IC₅₀ values in range of 2.7 ± 0.320-109.2 ± 3.217 μM. Molecular docking studies were used for interactions pattern and structure-activity relationship for all compounds, which demonstrated excellent binding interactions with the active site residues, such as hydrogen bonding, π-π interactions, π-H and nickel atom coordination.

Enzyme Inhibitory Kinetics and Molecular Docking Studies of Halo-Substituted Mixed Ester/Amide-Based Derivatives as Jack Bean Urease Inhibitors

A series of halo-substituted mixed ester/amide-based analogues 4a-l have been prepared as jack bean urease inhibitor, which showed good to excellent inhibition of enzyme activity. The role of halo-substituted benzoyl moieties and alkyl substituted anilines in urease inhibitory kinetics was also investigated. The alkyl-substituted anilines 1a-b reacted with chloroacetyl chloride to afford intermediates 2a-b, which were then reacted with different halo-substituted benzoic acids 3a-f to prepare the title compounds 4a-l. The chemical structures of final products 4a-l were ascertained by FTIR, 1H NMR, 13C NMR, and mass spectra. The compound 4b showed remarkable activity with IC501.6 ± 0.2 nM, better than the standard thiourea having IC50472.1 ± 135.1 nM. The 2-chloro-substituted phenyl ring on one side of compound 4b and 4-isopropyl-substituted benzene on the other side play an essential role in inhibition of urease activity. Lineweaver-Burk plots (kinetics study) indicated about 4b derivative as a mixed type of inhibitor. The virtual screening performed against urease enzyme (PDBID 4H9M) showed that compounds 4b and 4e have binding energies of -7.8 and -7.9 Kcal/mol, respectively. Based upon our results, it was found that derivative 4b is a highly potent urease inhibitor, better than the standard thiourea.

Flavonoid analogues as urease inhibitors: Synthesis, biological evaluation, molecular docking studies and in-silico ADME evaluation

A series of novel flavonoid analogues were designed and synthesized. The aimed compounds for urease inhibitory activities were clearly superior to the control drug thiourea (more than 10 times). Among these compounds, L2 (IC₅₀ = 1.343 µM) and L12 (IC₅₀ = 1.207 µM) exhibited the most excellent urease inhibitory activity in vitro. The molecular dockings of L2, L12 and L22 into urease were performed to explore the binding modes and their structure-activity relationship. Furthermore, these aimed compounds showed good druggable properties.

Bioassay-guided isolation and identification of anti-ulcer ecdysteroids from the seeds of Sphenocentrum jollyanum Pierre (Menispermaceae)

Sphenocentrum jollyanum seeds (MeOH extract and n butanol fraction) exhibited urease inhibitory activity (IC₅₀ 40.0 ± 0.92, 28.6 ± 0.41). The Ethyl acetate (EtOAc) fraction gave significant antacid activity with an increase in the baseline pH value of 1.2 to 1.61 ± 0.00 and 1.53 ± 0.00 at 50 and 100 mg, respectively, compared to the antacid activity of sodium bicarbonate (1.53 ± 0.00, 1.47 ± 0.00). Five known ecdysteroid compounds isolated from S. jollyanum ethyl acetate and n butanol fractions are Pinnatasterone (1), Polypodine B (2), 20-hydroxyecdysone (3), 20, 26-dihydroxyecdysone, (4) and Atrotosterone A (5). The compounds' structures were determined using extensive 1D and 2D NMR experiments, and the molecular mass for each of the compounds was confirmed by FAB-MS. Compounds 1-5 were evaluated for their urease inhibitory and antacid activities. Fractions were active in comparison with the standard drug acetohydroxamic acid, and sodium bicarbonate, respectively. Compounds 2, 3 and 1 showed significant urease inhibitory activity (IC₅₀ 7.0 ± 0.56, 13.8 ± 0.49 and 14.1 ± 0.59), respectively. The activity of compounds 4 and 5 were moderate compared to that of acetohydroxamic acid (IC₅₀ value 20.3 ± 0.43). Very few compounds have been isolated from this plant despite the numerous biological activities reported for it. The antacid and urease inhibitory activities of this plant and isolated compounds are described for the first time.

Synthesis, in vitro urease inhibitory potential and molecular docking study of benzofuran-based-thiazoldinone analogues

In continuation of our work on enzyme inhibition, the benzofuran-based-thiazoldinone analogues (1-14) were synthesized, characterized by HREI-MS, 1H and 13CNMR and evaluated for urease inhibition. Compounds 1-14 exhibited a varying degree of urease inhibitory activity with IC50 values between 1.2 ± 0.01 to 23.50 ± 0.70 µM when compared with standard drug thiourea having IC50 value 21.40 ± 0.21 µM. Compound 1, 3, 5 and 8 showed significant inhibitory effects with IC50 values 1.2 ± 0.01, 2.20 ± 0.01, 1.40 ± 0.01 and 2.90 ± 0.01 µM respectively, better than the rest of the series. A structure activity relationship (SAR) of this series has been established based on electronic effects and position of different substituents present on phenyl ring. Molecular docking studies were performed to understand the binding interaction of the compounds.

N’-(2-Hydroxybenzylidene)-3-Methylbenzohydrazide and its Copper(II) Complex: Syntheses, Characterization, Crystal Structures and Biological Activity

The hydrazone compound N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide (H2L) was prepared. With H2L and copper acetate a new copper complex [Cu(HL)(NCS)]·CH3OH was synthesized. Both the hydrazone and the copper complex were characterized by physico-chemical methods and single crystal X-ray diffraction techniques. The complex is a thiocyanato-coordinated copper(II) species. The Cu atom in the complex is in square planar geometry. The complex is a promising urease inhibitor.

Synthesis and spectroscopic characterization of novel methoxy bridged benzimidazolyl-substituted phthalocyanines as potent inhibitors of urease

In this study, novel peripherally 4-[(1H-benzimidazol-1-yl)methoxy] substituted Zn(II) (3) Cu(II) (4) and Co(II) (5) phthalocyanines were prepared and their structures were characterized spectroscopically. The light absorption behaviors of the synthesized compounds (3-5) were studied by UV-Vis spectroscopy at different concentrations in different solvents. The urease inhibition activities of the synthesized compounds were also investigated. Among the synthesized molecules, compound 4 showed the best inhibitory effect against jack bean urease with IC₅₀ values of 0.0036 ± 0.0010 μM.

Insight into the inhibitory effects of Zanthoxylum nitidum against Helicobacter pylori urease and jack bean urease: Kinetics and mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum nitidum (Roxb.) DC. is a traditional Chinese medicine characterised by anti-inflammatory and anti-Helicobacter pylori, which is widely used to treat H. pylori-induced gastric disease in China. However, the underlying mechanism related to its anti-H. pylori activity remains unclear. Urease plays a crucial role in the colonisation and survival of H. pylori.

AIM OF THE STUDY

The root aqueous extract of Z. nitidum against H. pylori urease (HPU) and jack bean urease (JBU) was investigated to illuminate the inhibitory potency, kinetics and potential mechanism.

MATERIALS AND METHODS

Z. nitidum components were determined by UPLC. The enzyme inhibitory effects of Z. nitidum were examined using modified spectrophotometric Berthelot (phenol-hypochlorite) method. Urease inhibition kinetics were determined by Lineweaver-Burk plots. Sulfhydryl group reagents and Ni²⁺-binding inhibitors were used in the mechanism study. Moreover, the molecular docking technique was used to investigate the binding conformations of the main compounds of Z. nitidum on Urease.

RESULTS

According to UPLC results, the major components of Z. nitidum were magnoflorine, sanguinarine, nitidine chloride, chelerythrine, skimmianine and L-Sesamin. Z. nitidum has higher enzyme inhibitory activity on HPU (IC₅₀ = 1.29 ± 0.10 mg/mL) than on JBU (IC₅₀ = 2.04 ± 0.27 mg/mL). Enzyme inhibitory kinetic analysis revealed that the type of Z. nitidum inhibition against HPU was a slow-binding and mixed-type, whereas a slow-binding and non-competitive type inhibited JBU. Further mechanism study indicated that the active site of sulfhydryl group might be the target of inhibition by Z. nitidum. The molecular docking study indicated that the above six main components of Z. nitidum exhibited stronger affinity to HPU than to JBU through interacting with the key amino acid residues located on the mobile flap or interacting with the active site Ni²⁺. Results indicated that these components are potential active ingredients directed against urease.

CONCLUSIONS

Z. nitidum inactivated urease in a concentration-dependent manner through slow-binding inhibition and binding to the urease active site sulfhydryl group. Our investigation might provide experimental evidence for the traditional application of Z. nitidum in the treatment of H. pylori-associated gastric disorders.

Biology-oriented drug synthesis (BIODS), in vitro urease inhibitory activity, and in silico studies on ibuprofen derivatives

Novel ibuprofen derivatives 1-19 including ibuprofen hydrazide 1, and substituted thiourea derivatives 2-19 were synthesized and characterized by EI-MS, FAB-MS, HREI-MS, HRFAB-MS, ¹H-, and ¹³C-NMR spectroscopic techniques. The synthetic molecules 1-19 were examined for their in vitro urease inhibition and were found to display a diversified degree of inhibitory potential in the range of IC₅₀ = 2.96-178 μM as compared to the standard thiourea (IC₅₀ = 21.32 ± 0.22 μM). Out of nineteen, thirteen derivatives 2-4, 6, 7, 9, 11-15, 17, and 18 demonstrated remarkable inhibitory activity with IC₅₀ values of 2.96 ± 1.11 to 16.1 ± 1.07 μM, compound 5 exhibited moderate inhibition with IC₅₀ value of 37.3 ± 0.41 μM, whereas, compounds 1, 8, and 10 demonstrated weak inhibition against urease enzyme. Almost all structural features are participating in the activity; however, limited structure-activity relationship was discussed on the basis of different structural features, i.e., different functional groups and their positions at aryl part. In addition, molecular docking study was performed in order to understand the ligands binding interactions with the active site of urease enzyme.

Novel N,N-dimethylbarbituric-pyridinium derivatives as potent urease inhibitors: Synthesis, in vitro, and in silico studies

A new series of N,N-dimethylbarbituric-pyridinium derivatives 7a-n was synthesized and evaluated as Helicobacter pylori urease inhibitors. All the synthesized compounds (IC₅₀ = 10.37 ± 1.0-77.52 ± 2.7 μM) were more potent than standard inhibitor hydroxyurea against urease (IC₅₀ = 100.00 ± 0.2 μM). Furthermore, comparison of IC₅₀ values of the synthesized compounds with the second standard inhibitor thiourea (IC₅₀ = 22.0 ± 0.03 µM) revealed that compounds 7a-b and 7f-h were more potent than thiourea. Molecular modeling study of the most potent compounds 7a, 7b, 7f, and 7g was also conducted. Additionally, the drug-likeness properties of the synthesized compounds, based on Lipinski rule and other filters, were evaluated.

Effect of patchouli alcohol on macrophage mediated Helicobacter pylori digestion based on intracellular urease inhibition

BACKGROUND

Helicobacter pylori infects almost half of the world population and is listed as a type I carcinoma factor since 1994. Pogostemon cablin (Blanco) Benth. (Labiatae) has been used to treat gastro-intestinal diseases for thousands of years in many east Asian countries, and the key ingredient, patchouli alcohol (PA), has been observed to exert anti-H. pylori and anti-urease activities.

PURPOSE

We investigated the effect of PA on H. pylori urease and its subsequent influence on macrophage phagosome maturation and function.

METHODS

In H. pylori experiment, the berthelot method and pH shock assay were adopted to evaluate the effect of PA on extracellular and intracellular H. pylori urease. And then, Q-PCR and Western blot were carried out to analyze the alterations in the expression of urease-related genes and proteins after PA treatment. In the H. pylori and macrophage cell (RAW264.7) co-culture experiment, the effects of PA on H. pylori-induced phagocytosis and intracellular killing of RAW264.7 were investigated using gentamycin protection assay, and the underlying mechanism was explored by immunofluorescence.

RESULTS

PA at 25 and 50 μM inhibited intracellular H. pylori urease activity but not isolated urease by down-regulating the gene expression levels of ureB, ureE, ureI and nixA and reducing the protein expression level of UreB, thereby inhibiting the acid resistance of H. pylori. PA also recovered the function of macrophage bacterial digestion, and prior treatment with ammonium chloride inhibited the efficacy of PA.

CONCLUSION

PA suppressed intracellular H. pylori urease function and maturation, which increased macrophage digestion ability.

Toxicity comparison of three imidazolium bromide ionic liquids to soil microorganisms

Ionic liquids (ILs) are extensively used in several chemistry fields. And research about the effects of ILs on soil microbes is needed. In this study, brown soil was exposed to 1-butyl-3-methylimidazolium bromide ([C₄mim]Br), 1-hexyl-3-methylimidazolium bromide ([C₆mim]Br) and 1-decyl-3-methylimidazolium bromide ([C₁₀mim]Br). The toxicities of the three ILs are evaluated by measuring the soil culturable microbial number, enzyme activity, microbial diversity and, abundance of the ammonia monooxygenase (amoA) genes of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Results showed that all tested ILs caused a decrease in culturable microbial abundance. Tested ILs exposure inhibit urease activity and promote acid phosphatase and β-glucosidase activities. Tested ILs reduced soil microbial diversity and the abundances of AOB-amoA and AOA-amoA genes significantly. After a comparison of the integrated biomarker response (IBR) index, the toxicities of tested ILs to soil microorganisms were as follows: [C₁₀mim]Br > [C₆mim]Br > [C₄mim]Br. Among all collected biomarkers, the abundance of the AOA-amoA gene was the most sensitive one and was easily affected after ILs exposure.

In Silico and In Vitro Anti-Helicobacter Pylori Effects of Combinations of Phytochemicals and Antibiotics

Helicobacter pylori infection is a WHO class 1 carcinogenic factor of gastric adenocarcinoma. In the past decades, many studies have demonstrated the increasing trend of antibiotic resistance and pointed out the necessity of new effective treatment. This study was aimed at identifying phytochemicals that can inhibit H. pylori and possibly serve as adjuvant treatments. Here, in silico molecular docking and drug-like properties analyses were performed to identify potential inhibitors of urease, shikimate kinase and aspartate-semialdehyde dehydrogenase. These three enzymes are targets of the treatment of H. pylori. Susceptibility and synergistic testing were performed on the selected phytochemicals and the positive control antibiotic, amoxicillin. The in-silico study revealed that oroxindin, rosmarinic acid and verbascoside are inhibitors of urease, shikimate kinase and aspartate-semialdehyde dehydrogenase, respectively, in which, oroxindin has the highest potency against H. pylori, indicated by a minimum inhibitory concentration (MIC) value of 50 μg/mL. A combination of oroxindin and amoxicillin demonstrated additive effects against H. pylori, as indicated by a fractional inhibitory concentration (FIC) value of 0.75. This study identified phytochemicals that deserve further investigation for the development of adjuvant therapeutic agents to current antibiotics against H. pylori.

Utility of anthranilic acid and diethylacetylenedicarboxylate for the synthesis of nitrogenous organo/organometallic compounds as urease inhibitors

Fumarate diester 3 was synthesized upon reacting anthranilic acid with diethylacetylenedicarboxylate. Compound 3 was reacted with different nucleophiles in mild reaction conditions. Selected reaction routes that afforded products 6, 9, 10, 11, and 12 were explained. The estimated mechanism for the reaction of 3 with ethylenediamine to afford 9 was proved by X-ray single-crystal and retro-synthetic reaction. Acetyl anthranilic acid was utilized with zinc and copper to afford the organometallic compounds 14a and 14b, respectively. Three single crystals were afforded for 3, 9 and the organocopper complex 14b. Target compounds were screened for their inhibitory potential against urease enzyme. Most compounds were more potent than thiourea as standard inhibitor, considering that oxopiperazine 9 exhibited double the activity: IC₅₀ = 8.16 ± 0.65 µM (thiourea IC₅₀ = 20.04 ± 0.33 µM). Docking studies were in agreement with the in vitro enzyme assay.

Studies on Isoniazid Derivatives through a Medicinal Chemistry Approach for the Identification of New Inhibitors of Urease and Inflammatory Markers

A library of thiosemicarbazide derivatives of isoniazid 3-27, was synthesized and evaluated for their anti-inflammatory and urease inhibition activities, by using in vitro bioassays. Among these compounds 9, 10, 12, 21, and 26 were identified as new derivatives. Prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs) and infections caused by Helicobacter pylori (ureolytic bacteria), are the two most significant causes of gastric and peptic ulcers. We focused on the identification of the dual inhibitors of inflammation and urease enzyme. Compound 23 was identified as the best dual inhibitor of inflammation (ROS; IC50 = 12.3 µg/mL), and urease enzyme inhibition activity (IC50 = 22.4 µM). Many of these compounds showed comparable activities to the standard anti-inflammatory drug (ibuprofen, IC50 = 11.2 µg/mL) and urease inhibitor (thiourea/acetohydraoxamic acid, IC50 = 21.1/20.3 µM). Compound 12 was found to be the most potent urease inhibitor (IC50 = 12.3 µM) and good inhibitor of inflammation (IC50 = 27.7 µg/mL). Compounds 19, 11, 13, 9, 17, 10, and 16, were also found to be potent inhibitors of urease. Cytotoxicity was also evaluated and all the compounds were found to be non-cytotoxic, except compound 18 and the parent drug isoniazid (IC50 = 29.5 and 28.5 µM, respectively).

Synthesis, characterization, antimicrobial and enzyme inhibitory studies of moxifloxacin with aromatic carboxylic acids

A series of carboxamide derivatives of moxifloxacin has been synthesized. The synthesized derivatives has been characterization by using spectroscopic techniques such as UV-Vis, IR, H1NMR and Mass spectra, which suggested that incoming group has occupied azabicylo groups of selected moxifloxacin at 7th position. Antimicrobial screening has been systematically carried out against various gram-positive, Gram-negatives and fungi in comparison with parent drug. Enzymatic assay were also performed. The results obtained were statistically analyzed by one way ANOVA. The antimicrobial results reveals that the synthesized derivative of moxifloxacin possess good activities against B. subtilis, F. solani, T. rubrum and P. aeruginosa concluding that derivatives are more potent antimicrobial agents as compared to parent drug. While compound B1 solely possess mild enzymatic activity against urease whereas, no other compounds is active against both urease and carbonic anhydrase.

Heterochelates of metals as an effective anti - Urease agents couple with their docking studies

The current article discusses the activities of several synthesized metal heterochelates in in-vitro as anti-ulcer agents followed by their docking study. For this purpose, two important ligands like 8-hydroxyquinoline and DL-methionine were used in synthesis of heterochelates of metal including Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II), Cd (II) and Pb (II). It was observed that these complexes showed excellent urease inhibition activities in which thiourea was the standard having IC50 value 21.6 ± 0.12μM. The Cu (II) complex showed potent inhibitory activity (22.6 ± 0.72 μM) when compared with the standard thiourea (21.6±0.12μM) among the nine synthesized complexes while Mn (II), Fe (III), Cd (II) and Pb (II) also showed better inhibitory activities. The urease inhibitory activities of hetercochelates also tested and validated by docking analysis.

Synthesis, spectral analysis and biological evaluation of sulfamoyl and 1,3,4-oxadiazole derivatives of 3-pipecoline

Heterocyclic chemistry is an important field of organic chemistry due to therapeutic potential. The minor modification in the structure of poly-functional compounds has great effect on therapeutic ability. In the presented research work, substituted 1,3,4-oxadiazole derivatives, 8a-p, have been synthesized by the reaction of 1-(4-bromomethylbenzenesulfonyl)-3-methylpiperidine (7) and 5-substituted-1,3,4-oxadiazole-2-thiol (4a-p). The 5-substituted-1,3,4-oxadiazole-2-thiol were synthesized by converting carboxylic acids correspondingly into esters, hydrazides and oxadiazoles. Secondly the electrophile, 1-(4-Bromomethylbenzenesulfonyl)-3-methylpiperidine (7), was prepared by the reaction of 3-methylpiperidine with 4-bromomethylbenzenesulfonyl chloride in the presence of water and Na₂CO₃ under pH of 9-10. The compounds were structurally corroborated through spectroscopic data analysis of IR, EI-MS and 1H-NMR. The screening for antibacterial activity revealed the compounds to be moderate to excellent inhibitors against bacteria under study. Anti-enzymatic activity was assessed against urease enzyme and 1-{[4-({[5-(3-nitrophenyl)-1,3,4-oxadiazol-2-yl]sulfanyl}methyl)phenyl]sulfonyl}-3-methylpiperidine (8d) was the most active one.

Insights into Urease Inhibition by N-( n-Butyl) Phosphoric Triamide through an Integrated Structural and Kinetic Approach

The nickel-dependent enzyme urease represents a negative element for the efficiency of soil nitrogen fertilization as well as a virulence factor for a large number of pathogenic and antibiotic-resistant bacteria. The development of ever more efficient urease inhibitors demands knowledge of their modes of action at the molecular level. N-( n-Butyl)-phosphoric triamide (NBPTO) is the oxo-derivative of N-( n-butyl)-thiophosphoric triamide (NBPT), which is extensively employed in agriculture to increase the efficiency of urea-based fertilizers. The 1.45 Å resolution structure of the enzyme-inhibitor complex obtained upon incubation of Sporosarcina pasteurii urease (SPU) with NBPTO shows the presence of diamido phosphoric acid (DAP), generated upon enzymatic hydrolysis of NBPTO with the release of n-butyl amine. DAP is bound in a tridentate binding mode to the two Ni(II) ions in the active site of urease via two O atoms and an amide NH₂ group, whereas the second amide group of DAP points away from the metal center into the active-site channel. The mobile flap modulating the size of the active-site cavity is found in a disordered closed-open conformation. A kinetic characterization of the NBPTO-based inhibition of both bacterial (SPU) and plant ( Canavalia ensiformis or jack bean, JBU) ureases, carried out by calorimetric measurements, indicates the occurrence of a reversible slow-inhibition mode of action. The latter is characterized by a very small value of the equilibrium dissociation constant of the urease-DAP complex caused, in turn, by the large rate constant for the formation of the enzyme-inhibitor complex. The much greater capability of NBPTO to inhibit urease, as compared with that of NBPT, is thus not caused by the presence of a P═O moiety versus a P═S moiety, as previously suggested, but rather by the readiness of NBPTO to react with urease without the need to convert one of the P-NH₂ amide moieties to its P-OH acid derivative, as in the case of NBPT. The latter process is indeed characterized by a very small equilibrium constant that reduces drastically the concentration of the active form of the inhibitor in the case of NBPT. This indicates that high-efficiency phosphoramide-based urease inhibitors must have at least one O atom bound to the central P atom in order for the molecule to efficiently and rapidly bind to the dinickel center of the enzyme.

Symmetrical Heterocyclic Cage Skeleton: Synthesis, Urease Inhibition Activity, Kinetic Mechanistic Insight, and Molecular Docking Analyses

The present study focuses on the design and synthesis of a cage-like organic skeleton containing two triazole rings jointed via imine linkage. These molecules can act as urease inhibitors. The in-vitro urease inhibition screening results showed that the combination of the two triazole skeleton in the cage-like morphology exhibited comparable urease inhibition activity to that of the reference thiourea while the metallic complexation, especially with copper, nickel, and palladium, showed excellent activity results with IC50 values of 0.94 ± 0.13, 3.71 ± 0.61, and 7.64 ± 1.21 (3a⁻c), and 1.20 ± 0.52, 3.93 ± 0.45, and 12.87 ± 2.11 µM (4a⁻c). However, the rest of compounds among the targeted series exhibited a low to moderate enzyme inhibition potential. To better understand the compounds' underlying mechanisms of the inhibitory effect (3a and 4a) and their most active metal complexes (3b and 4b), we performed an enzymatic kinetic analysis using the Lineweaver⁻Burk plot in the presence of different concentrations of inhibitors to represent the non-competitive inhibition nature of the compounds, 3a, 4a, and 4b, while mixed type inhibition was represented by the compound, 3b. Moreover, molecular docking confirmed the binding interactive behavior of 3a within the active site of the target protein.

Antimicrobial and antiurease potential of Diorganotin(IV) Schiff bases

The total phenolic content, flavonoid content, in vitro xanthine oxidase (XOD) inhibitory activity and antioxidant activity (AA) of Eucommia ulmoides Oliver leaf extracts were investigated. The AA investigations included 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, β-carotene/linoleic acid bleaching assay and oxygen radical absorbance capacity (ORAC) test. The ethyl acetate fraction (EE) showed the highest AA and xanthine oxidase inhibitory activity. Whilst the lowest 50% inhibition (IC₅₀) value of this fraction for DPPH free radical scavenging was 0.045mg/mL, its highest ORAC value was 10.57 μmol TE/mg. The highest inhibition rate against linoleic acid oxidation observed was 69.41%, and the lowest IC₅₀ value for xanthine oxidase activity inhibition was 2.47mg/mL. These results show that E. ulmoides leaf extract is a promising source of natural antioxidants because it contains high contents of bioactive compounds, including chlorogenic acid, rutin, hyperin and astragalin, as detected by high-performance liquid chromatography coupled to HPLC-DAD-ESI-MS.

Synthesis and in vitro Bio-activity Evaluation of N4-benzyl Substituted 5-Chloroisatin-3-thiosemicarbazones as Urease and Glycation Inhibitors

A series of fifteen N4-benzyl substituted 5-chloroisatin-3-thiosemicarbazones 5a-o were synthesized and screened mainly for their antiurease and antiglycation effects. Lemna aequinocitalis growth and Artemia salina assays were carried out to determine their phytotoxicity and cytotoxicity potential. All the compounds proved to be extremely effective urease inhibitors, demonstrating enzyme inhibition much better than the reference inhibitor, thiourea (IC50 values 1.31 ± 0.06 to 3.24 ± 0.15 vs. 22.3 ± 1.12 μM). On the other hand, eight out of fifteen compounds tested, i.e. 5b, 5c, 5h-k, 5m and 5n were found to be potent glycation inhibitors. Of these, five viz. 5c, 5h-j and 5n proved to be exceedingly efficient, displaying glycation inhibition greater than the reference inhibitor, rutin (IC50 values 114.51 ± 1.08 to 229.94 ± 3.40 vs. 294.5 ± 1.5 μM).

A novel inhibition based biosensor using urease nanoconjugate entrapped biocomposite membrane for potentiometric glyphosate detection

A potentiometric biosensor based on agarose-guar gum (A-G) entrapped bio-nanoconjugate of urease with gold nanoparticles (AUNps), has been reported for the first time for glyphosate detection. The biosensor is based on inhibition of urease activity by glyphosate, which was measured by direct potentiometry using ammonium ion selective electrode covered with A-G-urease nanoconjugate membrane. TEM and FTIR analysis revealed nanoconjugate formation and its immobilization in A-G matrix respectively. The composite biopolymer employed for immobilization yields thin, transparent, flexible membrane having superior mechanical strength and stability. It retains the maximum activity (92%) of urease with negligible leaching. The conjugation of urease with AUNps allows improvement in response characteristics for potentiometric measurement. The biosensor shows a linear response in the glyphosate concentration range from 0.5ppm-50ppm, with limit of detection at 0.5ppm, which covers maximum residual limit set by WHO for drinking water. The inhibition of catalytic activity of urease nanoconjugate by gyphosate was confirmed by FTIR analysis. The response of fabricated biosensor is selective towards glyphosate as against various other pesticides. The biosensor exhibits good performance in terms of reproducibility and prolonged storage stability of 180days. Thus, the present biosensor provides an alternative method for simple, selective and cost effective detection of glyphosate based on urease inhibition.

Phytochemical composition, biological potential and enzyme inhibition activity of Scandix pecten-veneris L

OBJECTIVE

Scandix pecten-veneris L. is a less studied wild edible herb and is considered an extinct plant species in many parts of the world. This study was designed to evaluate its phytochemical composition and biological potential of S. pecten-veneris L.

METHODS

Phytochemicals including alkaloids, flavonoids, polyphenols, and tannins were determined in extracts of S. pecten-veneris. Antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), while reducing power was tested by ferric reducing/antioxidant power (FRAP) assay. Antimicrobial activity against seven bacterial and four fungal strains was evaluated using agar well diffusion assay. Enzymes inhibition study was performed for urease, phosphodiesterase-I, and catalase-II.

RESULTS

S. pecten-veneris showed moderate antiradical activity and reducing potential of hydroxyl radicals to about 20% of the initial value. The antioxidant activity of various extracts of S. pecten-veneris showed a linear correlation with total phenolic contents in the order of water>n-butanol>chloroform>ethyl acetate>methanol extracts. S. pecten-veneris leaves showed the highest inhibitory activity against Staphylococcus aureus while the highest antifungal activity was observed against Candida albicans. The plant extract was most potent against urease enzymes but showed moderate activity against phosphodiestrase-I and carbonic anhydrase-II.

CONCLUSIONS

Our data demonstrate that in addition to its culinary uses, S. pecten-veneris has good medicinal potential and hence could be used for treating some specific health ailments.

Metallochaperone UreG serves as a new target for design of urease inhibitor: A novel strategy for development of antimicrobials

Urease as a potential target of antimicrobial drugs has received considerable attention given its versatile roles in microbial infection. Development of effective urease inhibitors, however, is a significant challenge due to the deeply buried active site and highly specific substrate of a bacterial urease. Conventionally, urease inhibitors are designed by either targeting the active site or mimicking substrate of urease, which is not efficient. Up to now, only one effective inhibitor—acetohydroxamic acid (AHA)—is clinically available, but it has adverse side effects. Herein, we demonstrate that a clinically used drug, colloidal bismuth subcitrate, utilizes an unusual way to inhibit urease activity, i.e., disruption of urease maturation process via functional perturbation of a metallochaperone, UreG. Similar phenomena were also observed in various pathogenic bacteria, suggesting that UreG may serve as a general target for design of new types of urease inhibitors. Using Helicobacter pylori UreG as a showcase, by virtual screening combined with experimental validation, we show that two compounds targeting UreG also efficiently inhibited urease activity with inhibitory concentration (IC)₅₀ values of micromolar level, resulting in attenuated virulence of the pathogen. We further demonstrate the efficacy of the compounds in a mammalian cell infection model. This study opens up a new opportunity for the design of more effective urease inhibitors and clearly indicates that metallochaperones involved in the maturation of important microbial metalloenzymes serve as new targets for devising a new type of antimicrobial drugs.

Urease, a metalloenzyme that catalyzes the hydrolysis of urea, plays important roles in the survival and virulence of many microbial pathogens, and has long been considered an important drug target for the development of novel antimicrobials. However, its deeply buried active site and highly specific substrate of bacterial urease make it very challenging to design effective urease inhibitors by conventional approaches. In this study, we reveal that a bismuth-based drug (colloidal bismuth subcitrate) inhibits urease activity in an unusual way. This drug binds the urease accessary protein UreG and inhibits its GTPase activity, thus perturbing nickel insertion into the apo-urease, a process called urease maturation. UreG is therefore proposed as an alternative target for the development of urease inhibitors. Using H. pylori UreG as an example, combined with virtual screening and experimental validation, we further show that several small molecules that bind and functionally disrupt UreG could indeed inhibit urease activity in bacteria and in a cell infection model and possess potent antimicrobial activity. In summary, we discovered metallochaperone UreG as a new target for the design of urease inhibitors. Such a strategy should have a broad application in the development of metalloenzyme inhibitors.

Characterization of New Bioactive Enzyme Inhibitors from Endophytic Bacillus amyloliquefaciens RWL-1

Endophytic bacteria are known to produce a wide array of bioactive secondary metabolites with beneficial effects on human health. In the current study, a novel endophytic bacterial strain, Bacillus amyloliquefaciens RWL-1, was isolated from the seeds of Oryza sativa. Initially, the crude extract of RWL-1 was assessed for potential biological effects of enzyme inhibition and cytotoxicity and was found to exhibit a broad spectrum inhibition for α-glucosidase (37 ± 0.09%) and urease (49.4 ± 0.53%). The screening results were followed by bioassay-guided isolation of secondary metabolite(s) from RWL-1. Extensive chromatographic and spectrophotometry analyses revealed the presence of compound 1 (S)-2-hydroxy-N-((S)-1-((S)-8-hydroxy-1-oxoisochroman-3-yl)-3-methylbutyl)-2-((S)-5-oxo-2,5-dihydrofuran-2-yl)acetamide. Further bioassays of compound 1 showed significant inhibition of α-glucosidase (52.98 ± 0.8%) and urease (51.27 ± 1.0%), compared with positive control values of 79.14 ± 1.9% and 88.24 ± 2.2%, and negative controls (0.08 ± 0.1% and 0.05 ± 0.01%), respectively. The current study suggests that bacterial endophytes are a rich source of novel bioactive compounds with high therapeutic value.

Isolation, characterization, and in silico, in vitro and in vivo antiulcer studies of isoimperatorin crystallized from Ostericum koreanum

CONTEXT

Ostericum koreanum (Maxim.) Kitagawa (Apiaceae) roots are traditionally used as an analgesic and antiulcer agent. However, the antiulcer potential of isoimperatorin isolated from O. koreanum has not yet been explored.

AIM

To evaluate the antiulcer activity of isoimperatorin isolated from the roots of O. koreanum.

MATERIALS AND METHODS

Isoimperatorin was isolated as cubic crystals by repeated column chromatography of the ethyl acetate fraction and structure was verified with ¹H NMR, ¹³C NMR and high-resolution mass spectrometry (HRMS-FAB). The crystals obtained were analyzed with the single crystal X-ray method. The MTT assay was used to determine its cytotoxicity against chondrocytes at different concentrations (0.0-737.74 μM, 24 h). The in vivo antiulcer activity of isoimperatorin (40 mg/kg) was determined against ethanol-, indomethacin- and pyloric ligation-induced ulcers in Sprague-Dawley rats. Furthermore, the effect of isoimperatorin (0.0-737.74 μM, 24 h) on the expression of type II collagen in chondrocytes was determined using western blot method. The in vitro urease inhibitory activity of isoimperatorin (0-80 μM) and molecular docking was also performed against urease.

RESULTS AND DISCUSSION

Isoimperatorin demonstrated significant inhibitory activity (IC₅₀ 36.43 μM) against urease as compared to the standard drug thiourea (IC₅₀ 33.57 μM) without cytotoxic effects. It provided 70.9%, 67.65% and 54.25% protection in ulcer models induced by ethanol, indomethacin and pyloric ligation, respectively. Isoimperatorin showed the highest expression level of type II collagen at 368.87 μM. The docking results confirmed strong binding affinity with the target protein.

CONCLUSION

Isoimperatorin may be used to develop antiulcer drugs with decreased side effects.

Biological Evaluation and Molecular Docking of Protocatechuic Acid from Hibiscus sabdariffa L. as a Potent Urease Inhibitor by an ESI-MS Based Method

Studies on enzyme inhibition remain a crucial area in drug discovery since these studies have led to the discoveries of new lead compounds useful in the treatment of several diseases. In this study, protocatechuic acid (PCA), an active compound from Hibiscus sabdariffa L. has been evaluated for its inhibitory properties against jack bean urease (JBU) as well as its possible toxic effect on human gastric epithelial cells (GES-1). Anti-urease activity was evaluated by an Electrospray Ionization-Mass Spectrometry (ESI-MS) based method, while cytotoxicity was assayed by the MTT method. PCA exerted notable anti-JBU activity compared with that of acetohydroxamic acid (AHA), with IC50 values of 1.7 and 3.2 µM, respectively. PCA did not show any significant cytotoxic effect on (GES-1) cells at concentrations ranging from 1.12 to 3.12 µM. Molecular docking study revealed high spontaneous binding ability of PCA to the active site of urease. Additionally, the anti-urease activity was found to be related to the presence of hydroxyl moieties of PCA. This study presents PCA as a natural urease inhibitor, which could be used safely in the treatment of diseases caused by urease-producing bacteria.

Short Communication - Urease inhibitory activity of Hippophae rhamnoids and Cassia fistula

The rational use of plants as medicine is traced back over five epochs to ancient documents of early civilizations and is certainly as old as mankind. These medicines originally developed from crude drugs like tinctures and tinctures. Minimum 119 chemical substances are derived from 90 plant species and used all over the world as medicines, several of them containing compounds derived from or modelled after naturally occurring lead molecules and 74% of these derived from orthodox medicinal plants. 252 drugs (11%) are believed to be basic and essential by the WHO and are exclusively of plant origin. We have examined anti-urease activity of ethyl alcohol (Et-OH) and methyl alcohol (Me-OH) extracts of H. rhamnoides and Cassia fistula. Berthelot assay was used for the determination of anti-urease activity. The enzyme activity and inhibition was measured through catalytic effects of urease on urea by measuring change in absorbance in the absence and in the presence of inhibitor at 625nm using UV spectrophotometer. In the study, both Et-OH and Me-OH extracts of H. rhamnoides (91.69%±1.21) and C. fisstula (79.44%±0.55) showed stronger action against urease activity. An overview on the medicinal uses of H. rhamnoides and C. fisstula showing anti-urease activity may predict their possible alternative use for stomach problems. This study may help to explain the beneficial effects of these plants against stomach infection associated with pathogenic strains of H. pylori as Urease is the most prominent protein component of H. pylori.

Aminophosphinates against Helicobacter pylori ureolysis-Biochemical and whole-cell inhibition characteristics

Urease is an important virulence factor from Helicobacter pylori that enables bacterial colonization of human gastric mucosa. Specific inhibition of urease activity can be regarded as a promising adjuvant strategy for eradication of this pathogen. A group of organophosphorus inhibitors of urease, namely, aminophosphinic acid and aminophosphonic acid derivatives, were evaluated in vitro against H. pylori urease. The kinetic characteristics of recombinant enzyme activity demonstrated a competitive reversible mode of inhibition with K_i values ranging from 0.294 to 878 μM. N-n-Hexylaminomethyl-P-aminomethylphosphinic acid and N-methylaminomethyl-P-hydroxymethylphosphinic acid were the most effective inhibitors (K_i = 0.294 μM and 1.032 μM, respectively, compared to K_i = 23 μM for the established urease inhibitor acetohydroxamic acid).

The biological relevance of the inhibitors was verified in vitro against a ureolytically active Escherichia coli Rosetta host that expressed H. pylori urease and against a reference strain, H. pylori J99 (CagA⁺/VacA⁺). The majority of the studied compounds exhibited urease-inhibiting activity in these whole-cell systems. Bis(N-methylaminomethyl)phosphinic acid was found to be the most effective inhibitor in the susceptibility profile studies of H. pylori J99. The cytotoxicity of nine structurally varied inhibitors was evaluated against four normal human cell lines and was found to be negligible.

Synthesis and molecular docking study of some 5,6-dichloro-2-cyclopropyl-1H-benzimidazole derivatives bearing triazole, oxadiazole, and imine functionalities as potent inhibitors of urease

A new series of benzimidazole compounds including hydrazinecarbothioamide, 1,2,4-triazole, 1,3,4-oxadiazole and imine function were synthesized starting from 5,6-dichloro-2-cyclopropyl-1H-benzimidazole. All of the benzimidazole derivatives exhibited good urease inhibitor activity. Compound 6a proved to be the most potent showing an enzyme inhibitory activity with an IC₅₀=0.06µM. Molecular docking studies were also conducted on enzyme extracted from Jack bean urease to identify the binding mode of the newly synthesized compounds.

Hibiscus sabdariffa L. and Its Bioactive Constituents Exhibit Antiviral Activity against HSV-2 and Anti-enzymatic Properties against Urease by an ESI-MS Based Assay

For decades, Hibiscus sabdariffa L. and its phytochemicals have been shown to possess a wide range of pharmacologic properties. In this study, aqueous extract of Hibiscus sabdariffa (AEHS) and its bioactive constituent protocatechuic acid (PCA), have been evaluated in vitro for their antiviral activity against HSV-2 clinical isolates and anti-enzymatic activity against urease. Antiherpetic activity was evaluated by the titer reduction assay in infected Vero cells, and cytotoxicity was evaluated by the neutral red dye-uptake method. Anti-urease activity was determined by a developed Electrospray Ionization-Mass Spectrometry (ESI-MS)-based assay. PCA showed potent anti-HSV-2 activity compared with that of acyclovir, with EC₅₀ values of 0.92 and 1.43 µg∙mL⁻¹, respectively, and selectivity indices > 217 and > 140, respectively. For the first time, AEHS was shown to exert anti-urease inhibition activity, with an IC₅₀ value of 82.4 µg∙mL⁻¹. This, combined with its safety, could facilitate its use in practical applications as a natural urease inhibitor. Our results present Hibiscus sabdariffa L. and its bioactive compound PCA as potential therapeutic agents in the treatment of HSV-2 infection and the treatment of diseases caused by urease-producing bacteria.

Synthesis of New Nitrofluoroquinolone Derivatives with Novel Anti-Microbial Properties against Metronidazole Resistant H. pylori

One of the major therapeutic approaches to preventing relapse and accelerating the healing of duodenal and gastric ulcers is the eradication of Helicobacter pylori. Due to the emergence of antibiotic resistance among clinical strains of H. pylori, alternative approaches using newly discovered antimicrobial agents in combination with the standard regimens for the treatment of H. pylori are increasingly needed. The purpose of the present study was to investigate the effect of newly synthesized 8-nitroflouroqunolone derivatives when used either alone or when combined with metronidazole against metronidazole-resistant H. pylori. Based on the standard antimicrobial susceptibility testing methods and checkerboard titration assay, all of the tested compounds showed interesting antimicrobial activity against 12 clinical strains of H. pylori, with the best in vitro effect for compound 3c. In addition, synergistic and additive activities of some of the tested compounds were observed when combined with metronidazole. Furthermore, among the tested nitroflouroquinolone derivatives, compound 3b showed significant urease inhibition activity with IC₅₀ of 62.5 µg/mL. These results suggest that 8-nitroflouroquinolone derivatives may have a useful role in combination with anti-H. pylori drugs in the management of H. pylori-associated diseases.

Inhibition of Helicobacter pylori and Its Associated Urease by Palmatine: Investigation on the Potential Mechanism

In this paper, we evaluated the anti-Helicobacter pylori activity and the possible inhibitory effect on its associated urease by Palmatine (Pal) from Coptis chinensis, and explored the potential underlying mechanism. Results indicated that Pal exerted inhibitory effect on four tested H. pylori strains (ATCC 43504, NCTC 26695, SS1 and ICDC 111001) by the agar dilution test with minimum inhibitory concentration (MIC) values ranging from 100 to 200 μg/mL under neutral environment (pH 7.4), and from 75 to 100 μg/mL under acidic conditions (pH 5.3), respectively. Pal was observed to significantly inhibit both H. pylori urease (HPU) and jack bean urease (JBU) in a dose-dependent manner, with IC50 values of 0.53 ± 0.01 mM and 0.03 ± 0.00 mM, respectively, as compared with acetohydroxamic acid, a well-known urease inhibitor (0.07 ± 0.01 mM for HPU and 0.02 ± 0.00 mM for JBU, respectively). Kinetic analyses showed that the type of urease inhibition by Pal was noncompetitive for both HPU and JBU. Higher effectiveness of thiol protectors against urease inhibition than the competitive Ni2+ binding inhibitors was observed, indicating the essential role of the active-site sulfhydryl group in the urease inhibition by Pal. DTT reactivation assay indicated that the inhibition on the two ureases was reversible, further supporting that sulfhydryl group should be obligatory for urease inhibition by Pal. Furthermore, molecular docking study indicated that Pal interacted with the important sulfhydryl groups and inhibited the active enzymatic conformation through N-H ∙ π interaction, but did not interact with the active site Ni2+. Taken together, Pal was an effective inhibitor of H. pylori and its urease targeting the sulfhydryl groups, representing a promising candidate as novel urease inhibitor. This investigation also gave additional scientific support to the use of C. chinensis to treat H. pylori-related gastrointestinal diseases in traditional Chinese medicine. Pal might be a potentially beneficial therapy for gastritis and peptic ulcers induced by H. pylori infection and other urease-related diseases.

Inhibition of Urease Enzyme Production and some Other Virulence Factors Expression in Proteus mirabilis by N-Acetyl Cysteine and Dipropyl Disulphide

Proteus mirabilis is one of the important pathogens that colonize the urinary tract and catheters resulting in various complications, such as blockage of the catheters and the formation of infective stones.

PURPOSE

In this study we evaluated the effect of N-acetyl cysteine (NAC) and dipropyl disulphide on some virulence factors expressed by a Proteus mirabilis strain isolated from a catheterized patient.

METHODS

Antibacterial activity of both compounds was determined by broth microdilution method. Their effect on different types of motility was determined by LB medium with variable agar content and sub-MIC of each drug. Their effect on adherence and mature biofilms was tested by tissue culture plate assay. Inhibitory effect on urease production was determined and supported by molecular docking studies.

RESULTS

The minimum inhibitory concentration (MIC) of NAC and dipropyl disulphide was 25 mM and 100 mM, respectively. Both compounds decreased the swarming ability and biofilm formation of the tested isolate in a dose-dependent manner. NAC had higher urease inhibitory activity (IC50 249 ±0.05 mM) than that shown by dipropyl disulphide (IC₅₀ 10±0.2 mM). Results were supported by molecular docking studies which showed that NAC and dipropyl disulphide interacted with urease enzyme with binding free energy of -4.8 and -8.528 kcal/mol, respectively. Docking studies showed that both compounds interacted with Ni ion and several amino acids (His-138, Gly-279, Cysteine-321, Met-366 and His-322) which are essential for the enzyme activity.

CONCLUSION

NAC and dipropyl disulphide could be used in the control of P. mirabilis urinary tract infections.

Antimicrobial Activity and Urease Inhibition of Schiff Bases Derived from Isoniazid and Fluorinated Benzaldehydes and of Their Copper(II) Complexes

In order to evaluate the influence of substitution on biological properties of Schiff bases and their metal complexes, a series of differently substituted fluorine-containing Schiff bases starting from the drug isoniazid (isonicotinylhydrazide) were prepared and their structures were established by single-crystal X-ray diffraction. Also, four copper(II) complexes of these Schiff bases were synthesized. The prepared compounds were evaluated for their antimicrobial activity and urease inhibition. Two of the Schiff bases exerted activity against C. albicans. All copper(II) complexes showed excellent inhibitory properties against jack bean urease, considerably better than that of the standard inhibitor acetohydroxamic acid.

Chemical speciation and enzymatic impact of silver in antimicrobial fabric buried in soil

This study investigated the impact of Ag in antibacterial fabric on soil enzymes in relation to solubility and speciation of Ag. Sections of Ag-containing sock fabric (1.0-1.5cm(2)) were incubated in soils with aerobic and anaerobic conditions and periodically determined activity of arylsulfatase, dehydrogenase and urease. Microscale distribution and speciation of Ag at the interface between socks and soil particles were investigated using micro-focused X-ray fluorescence (μ-XRF), and Ag speciation was determined using micro-focused X-ray absorption near edge structure (μ-XANES) spectroscopy. Results showed that the sock fabric consisted of elemental Ag and Ag2S. After 60-day exposure to soil, majority (50-90%) of Ag in sock did not undergo phase transformation and present as elemental Ag and Ag2S in aerobic and anaerobic conditions. A part of Ag in sock fabric was bound with soil colloids (<15%), depending on the distance from the edge of sock fabric. Soil enzyme activities were overall unaffected by Ag in sock textile after 60days of incubation, although a significant decrease in arylsulfatase activity was found only in the initial stage of soil incubation. Silver in the sock fabric is relatively stable and has little detrimental impacts on enzyme activity in ordinary soil conditions.