Synthesis and in vitro selective anti-Helicobacter pylori activity of N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides

A novel palladium complex with a coumarin-thiosemicarbazone hybrid ligand inhibits Trypanosoma cruzi release from host cells and lowers the parasitemia in vivo

In this work, two analogous coumarin-thio and semicarbazone hybrid compounds were prepared and evaluated as a potential antichagasic agents. Furthermore, palladium and platinum complexes with the thiosemicarbazone derivative as ligand (L1) were obtained in order to establish the effect of metal complexation on the antiparasitic activity. All compounds were fully characterized both in solution and in solid state including the resolution of the crystal structure of the palladium complex by X-ray diffraction methods. Unexpectedly, all experimental and theoretical characterizations in the solid state, demonstrated that the obtained palladium and platinum complexes are structurally different: [PdCl(L1)] and [PtCl2(HL1)]. All the studied compounds lower the proliferation of the amastigote form of Trypanosoma cruzi while some of them also have an effect on the trypomastigote stage. Additionally, the compounds inhibit T. cruzi release from host cells in variable extents. The Pd compound presented a remarkable profile in all the in vitro experiments, and it showed no toxicity for mammalian cells in the assayed concentrations. In this sense, in vivo experiments were performed for this compound using an acute model of Chagas disease. Results showed that the complex significantly lowered the parasite count in the mice blood with no significant toxicity.

Synthesis, Antibacterial and Antifungal Activity of New 3-Aryl-5H-pyrrolo[1,2-a]imidazole and 5H-Imidazo[1,2-a]azepine Quaternary Salts

A series of novel 3-aryl-5H-pyrrolo[1,2-a]imidazole and 5H-imidazo[1,2-a]azepine quaternary salts were synthesized in 58-85% yields via the reaction of 3-aryl-6, 7-dihydro-5H-pyrrolo[1,2-a]imidazoles or 3-aryl-6,7,8,9-tetrahydro-5H-imidazo[1,2-a]azepines and various alkylating reagents. All compounds were characterized by ¹H NMR, ¹³C NMR, and LC-MS. The conducted screening studies of the in vitro antimicrobial activity of the new quaternary salts derivatives established that 15 of the 18 newly synthesized compounds show antibacterial and antifungal activity. Synthesized 3-(3,4-dichlorohenyl)-1-[(4-phenoxyphenylcarbamoyl)-methyl]-6,7-dihydro-5H-pyrrolo[1,2-a]imidazol-1-ium chloride 6c possessed a broad activity spectrum towards Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Cryptococcus neoformans, with a high hemolytic activity against human red blood cells and cytotoxicity against HEK-293. However, compound 6c is characterized by a low in vivo toxicity in mice (LD₅₀ > 2000 mg/kg).

A review on the structures and biological activities of anti-Helicobacter pylori agents

Helicobacter pylori is one of the main causal risk factor in the generation of chronic gastritis, gastroduodenal ulcers and gastric carcinoma. Thus, the eradication of H. pylori infection is an important way for preventing and managing the gastric diseases. Multiple-therapy with several antibacterial agents is used for the eradication of H. pylori infections; however the increase of resistance to H. pylori strains has resulted in unsatisfactory eradication and unsuccessful treatment. Furthermore, the combination therapy with high dosing leads to the disruption of intestinal microbial flora and undesired side effects. Therefore, the search for new therapeutic agents with high selectivity against H. pylori is a field of current interest. In recent years, diverse compounds originating from natural sources or synthetic drug design programs were evaluated and tried to optimize for applying against H. pylori. In this review, we have described various classes of anti-H. pylori compounds, their structure-activity relationship studies, and mechanism of actions, which could be useful for the development of new drugs for the treatment of H. pylori infections.

Synthesis and Biological Activity Evaluation of Coumarin-3-Carboxamide Derivatives

A series of novel coumarin-3-carboxamide derivatives were designed and synthesized to evaluate their biological activities. The compounds showed little to no activity against gram-positive and gram-negative bacteria but specifically showed potential to inhibit the growth of cancer cells. In particular, among the tested compounds, 4-fluoro and 2,5-difluoro benzamide derivatives (14b and 14e, respectively) were found to be the most potent derivatives against HepG2 cancer cell lines (IC₅₀ = 2.62-4.85 μM) and HeLa cancer cell lines (IC₅₀ = 0.39-0.75 μM). The activities of these two compounds were comparable to that of the positive control doxorubicin; especially, 4-flurobenzamide derivative (14b) exhibited low cytotoxic activity against LLC-MK2 normal cell lines, with IC₅₀ more than 100 μM. The molecular docking study of the synthesized compounds revealed the binding to the active site of the CK2 enzyme, indicating that the presence of the benzamide functionality is an important feature for anticancer activity.

Secondary Antibiotic Resistance, Correlation between Genotypic and Phenotypic Methods and Treatment in Helicobacter pylori Infected Patients: A Retrospective Study

The aim of this study was to evaluate the secondary resistance in Helicobacter pylori (Hp) infected patients who had failed a first-line therapy, and to compare the genotypic tests performed directly on gastric samples with phenotypic tests performed on culture media. The eradication rate of patients treated with bismuth quadruple therapy (BQT) is also evaluated. A total of 80 positive specimens were retrospectively examined. Antibiotic susceptibility testing of Hp strains was performed by E-test, whereas a molecular commercially available method was used for detecting the mutations involved in clarithromycin and levofloxacin resistance. High resistance levels to metronidazole and clarithromycin (61.6% and 35%, respectively) and worrying resistance levels to levofloxacin (15%) were found phenotypically. Multiple resistance to two or three antibiotics was observed as well. The polymorphism A2143G on clarithromycin 23S rRNA gene was found in 34/80 (42.5%) isolates including 10 mixed infections (29%), whereas 28/80 (35%) strains were resistant phenotypically. Levofloxacin resistance corresponded to 30% by PCR and 15% by E-test (statistically significant, p < 0.05). The knowledge of clarithromycin and levofloxacin resistance is crucial to establish an appropriate therapy in different geographical areas. The genetic methods were superior to phenotypic techniques in the absence of live bacteria or for identifying mixed infections that may lead to a resistance underestimation. The BQT eradication rate was effective (90%).

A Primary Amide-Functionalized Heterogeneous Catalyst for the Synthesis of Coumarin-3-carboxylic Acids via a Tandem Reaction

A crystalline primary amide-based bifunctional heterogeneous catalyst, {[Cd₂(2-BPXG)(Fum)₂(H₂O)₂]·2H₂O}_n (1) (where, 2-BPXG = 2,2'-((1,4-phenylenebis(methylene))bis((pyridin-2-ylmethyl)azanediyl)) diacetamide and Fum = fumarate), has been developed for the one-pot synthesis of a series of potentially biologically active coumarin-3-carboxylic acids at room temperature via a Knoevenagel-intramolecular cyclization tandem reaction. Catalyst 1 is prepared at room temperature from a one-pot self-assembly process in 81% yield and high purity within a few hours and has a ladder-like polymeric architecture based on single-crystal X-ray diffraction. Additional characterization of 1 includes elemental analysis, infrared spectroscopy, thermogravimetric analysis, and powder X-ray diffraction. Based on the optimized conditions, it is determined that 1 is highly efficient (conditions: 2 mol % catalyst, 3 h, and 26-28 °C in methanol) for this reaction. Its recyclability up to five cycles without significant loss of activity and structural integrity is also demonstrated. Using both electron-donating and electron-withdrawing substituents on the salicylaldehyde substrate, seven different derivatives of coumarin-3-carboxylic acid were made. Additionally, the monoamine oxidase (MAO) inhibitor, coumarin-3-phenylcarboxamide, has also been synthesized from coumarin-3-carboxylic acid obtained in the catalysis process. A detailed mechanism of action is also provided.

Discovery of a Novel Mutation in DNA Gyrase and Changes in the Fluoroquinolone Resistance of Helicobacter pylori over a 14-Year Period: A Single Center Study in Korea

The efficacy of fluoroquinolone-based eradication therapy largely depends on the fluoroquinolone resistance of H. pylori. The aim of this study was to investigate the changes in the primary resistance rate of H. pylori to fluoroquinolone and the mechanism of resistance in Korea. A total of 153 strains and 48 strains of H. pylori were isolated at a tertiary hospital in 2005/2006 and 2017/2018, respectively. The minimum inhibitory concentrations (MICs) of fluoroquinolone were determined by the serial 2-fold agar dilution method. DNA sequences in the quinolone resistance-determining regions of gyrA/gyrB were analyzed in resistant strains. Subsequent natural transformation study was performed to determine the association between gyrase mutation and resistance. The resistance rates increased from 19.0% (29/153) to 43.8% (21/48) both for levofloxacin and moxifloxacin. The MIC values for resistant strains increased from 2–8 µg/mL to 4–16 µg/mL over time. Mutation of gyrA was detected in 93.1% (27/29) and 100% (21/21) among the resistant strains in both periods, respectively. A novel Gly-85 mutation of gyrA was found and confirmed to be associated with fluoroquinolone resistance. Fluoroquinolone resistance rate of H. pylori has markedly increased over time in Korea. The resistance is mostly due to the point mutation of gyrA. Fluoroquinolone-containing regimens should be carefully selected in Korea, considering the increasing fluoroquinolone resistance.

Diastereoselective multi-component tandem condensation: synthesis of 2-amino-4-(2-furanone)-4H-chromene-3-carbonitriles

A general strategy for a one-pot stereoselective synthesis of 2-amino-4-(2-furanone)-4H-chromene-3-carbonitriles by reaction of salicylaldehyde, malononitrile and butenolides via a tandem Knoevenagel/Pinner/vinylogous Michael condensation is presented. The β,γ-butenolides gave a syn-selective MCR adduct with a dr up to 11.5 : 1. The mechanistic insight into the MCR was obtained by DFT calculations.

Preparation and biological evaluation of metronidazole derivatives with monoterpenes and eugenol

Two series of metronidazole derivatives (ester derivatives and ether derivatives) were prepared reacting metronidazole and its acetic acid oxidized form with menthol, thymol, carvacrol, and eugenol. Both series of compounds were tested in vitro against two strains of Helicobacter pylori (the ATCC 26695 and P12), and one strain of Clostridium (Clostridium perfringens). Most of the prepared compounds showed biological activity against the targeted bacteria. Compound 11 was highly active against all tested bacterial strains, especially against P12 with IC₅₀ 0.0011 μM/ml. Compound 6 was highly active against C. perfringens with MIC 0.0094 nM/ml. Viability test was conducted for compound 11 to test its selectivity for normal human fetal lung fibroblasts (MRC5), and it was found to be non-toxic with IC₅₀ more than 50 μM/ml.

Coumarin: A Privileged Scaffold for the Design and Development of Antineurodegenerative Agents

Drug development for neurodegenerative diseases (NDs) is foremost task for the medicinal chemists in the 21st century. Coumarins are exemplary of an assorted and aptitudinally useful set of drugs. Coumarins play a momentous role in several pharmacological and medicinal aspects. Its analogues are anticipated to play a significant role in the development of new therapeutic leads for NDs. Their promising applications in the field of ND medication are exemplified by clinical candidates such as nodakenin that have been potent for demoting memory impairment. Apart from ND, clinically used anticoagulant warfarin, anticoagulant dicoumarol, and antibiotic coumermycin, novobiocin and chartesium grab the interest of researchers in coumarins. It would be worthwhile to look at the different biological processes that could cause neurodegeneration, thereby establishing a link with distinct coumarin derivatives to serve the purpose of medication. This review undertakes estimation of the wide spectrum of studies focusing coumarin to the domain of drug research for ND. Herein, we search for multitarget coumarin-based inhibitors and their scope for NDs. Future challenges in coumarin-based drug development have been discussed, and emphases have been laid on the future perspectives of coumarins as possible drugs in the future for the treatment of NDs.

BF3·Et2O Catalysed 4-Aryl-3-phenyl-benzopyrones, Pro-SERMs, and Their Characterization

We have synthesized the novel 4-(4-hydroxy-benzyl)-3-phenyl-chromen-2-one which is a precursor of SERMs with a smaller number of steps and good yield. Two methodologies for the synthesis have been worked out. Anhydrous BF3·Et2O catalyzed reaction was found to be selective for product formation while anhydrous AlCl3, FeCl3, and SnCl4 catalyzed ones were nonselective.

Bronsted acid-type biosurfactant for heterocyclization: a green protocol for benzopyran synthesis

Synthesis of benzopyran from the various salicylaldehydes and cyclic 1,3-diketones using catalytic amount of lemon extract as a green biosurfactant.

Glycine catalyzed convenient synthesis of 2-amino-4H-chromenes in aqueous medium under sonic condition

A one-pot three-component condensation of an aldehyde, malononitrile, and resorcinol has been achieved by ultrasound method. The reaction has been catalyzed by glycine in aqueous medium. This protocol afforded corresponding 2-amino-4H-chromenes in shorter reaction times, high yields and simple work-up procedures with the green aspects by avoiding toxic reagents.

Synthesis, molecular modeling, and selective inhibitory activity against human monoamine oxidases of 3-carboxamido-7-substituted coumarins

A large series of 3-carboxamido-7-substituted coumarins have been synthesized and tested in vitro for their human monoamine oxidase A and B (hMAO-A and hMAO-B) inhibitory activity. Taking into account all the relevant structural information on MAOs reported in the literature, we made some changes in the coumarin nucleus and examined with particular attention the effect on activity and selectivity of substituting at position 3 with N-aryl or N-alkyl carboxamide and at position 7 with a benzyloxy or a 4'-F-benzyloxy group. Some of the assayed compounds proved to be potent, selective inhibitors of hMAO-B with IC(50) values in the micromolar range. To better understand the enzyme-inhibitor interaction and to explain the selectivity of the most active compounds toward hMAOs, molecular modeling studies were carried out on new, high resolution, hMAO-A and hMAO-B crystallographic structures.

Antifungal activity of a novel chromene dimer

The activity on Aspergillus spp. growth and on ochratoxin A production of two novel chromene dimers (3) was evaluated. The results of the bioassays indicate that the chromene dimer 3a inhibited mycelia growth by approximately 50% (EC(50)) at 140.1 micromol L(-1) for A. niger, 384.2 micromol L(-1) for A. carbonarius, 69.1 micromol L(-1) for A. alliaceus and 559.1 micromol L(-1) for A. ochraceus. When applied at concentrations of 2 mmol L(-1), 3a totally inhibited the growth of all Aspergillus spp. tested. Furthermore, ochratoxin A production by A. alliaceus was reduced by about 94% with a 200 micromol L(-1) solution of this compound. A moderate inhibitory effect was observed for the analogous structure 3b on ochratoxin A production but not in mycelia growth. No inhibition was registered for compounds 2a and 2b, used as synthetic precursors of the dimeric species 3.

A novel class of selective anti-Helicobacter pylori agents 2-oxo-2H-chromene-3-carboxamide derivatives

A novel class of selective anti-Helicobacter pylori agents, 2-oxo-2H-chromene-3-carboxamide derivatives, were prepared and evaluated for their anti-bacterial activity. All synthesized compounds showed little or no activity against different species of Gram-positive and Gram-negative bacteria and against various strains of pathogenic fungi. Some of them exhibited a potent and specific inhibitory effect on the growth of H. pylori, including metronidazole-resistant strains, in the 0.0039-16 microg/mL MIC range. A cytotoxic screening by the Trypan blue dye exclusion assay was also carried out on the most active compounds as anti-H. pylori agents. Among the derivatives examined for their cytotoxic potential, a number of them induced low cytotoxic effects.

Synthesis and in vitro activity of 2-thiazolylhydrazone derivatives compared with the activity of clotrimazole against clinical isolates of Candida spp

In this paper, we report on the synthesis of a novel series of 2-thiazolylhydrazone derivatives and the influence of the substituents on the thiazole ring on antifungal activity. All synthesized compounds were screened for their in vitro activities against 22 clinical isolates of Candida spp., representing six different species, compared to clotrimazole as a reference compound. Some of the tested compounds were found to possess significant antifungal activity when compared to clotrimazole, in particular compound 14 which exhibited higher potency against most of the Candida spp. considered. The compounds that were most active as anti-Candida agents were also submitted to cytotoxic screening by the Trypan Blue dye exclusion assay and in general they were shown to induce low cytotoxic effects.

In vitro inhibitory activity of boropinic acid against Helicobacter pylori

In this study, we assessed in vitro minimum inhibitory concentration (MIC) values of some natural geranyloxycoumarins, geranyloxy- and isopentenyloxy acids against growth of Helicobacter pylori. Boropinic acid, active principle isolated from Boronia pinnata (Fam. Rutaceae), was seen to be the most effective compound with a MIC value of 1.62 microg/mL.