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.