Design, synthesis, and biological evaluation of Helicobacter pylori inosine 5'-monophosphate dehydrogenase (HpIMPDH) inhibitors

Anti-Helicobacter pylori, anti-biofilm activity, and molecular docking study of citropten, bergapten, and its positional isomer isolated from Citrus sinensis L. leaves

Introduction

Citrus sinensis L. is a candidate plant with promising antimicrobial potential. In the current study, the phytochemical investigation of C. sinensis leaf extract led to the isolation of three coumarins, namely bergapten, xanthotoxin, and citropten.

Methods

The chemical structures of the isolated coumarins were elucidated using NMR and ESI-MS techniques. The total aqueous ethanol leaf extract and the isolated coumarins were evaluated for their antimicrobial effects against Helicobacter pylori using the MTT-micro-well dilution method and its anti-biofilm activity using MBEC assay, as compared to clarithromycin.

Results

The results showed that citropten scored the lowest MIC value at 3.9 μg/mL and completely inhibited the planktonic growth of H. pylori. In addition, it completely suppressed H. pylori biofilm at 31.25 μg/mL. These findings have been supported by molecular docking studies on the active sites of the H. pylori inosine 5'-monophosphate dehydrogenase (HpIMPDH) model and the urease enzyme, showing a strong binding affinity of citropten to HpIMPDH with seven hydrogen bonds and a binding energy of -6.9 kcal/mol. Xanthotoxin and bergapten showed good docking scores, both at -6.5 kcal/mol for HpIMPDH, with each having four hydrogen bondings. Furthermore, xanthotoxin showed many hydrophobic interactions, while bergapten formed one Pi-anion interaction. Concerning docking in the urease enzyme, the compounds showed mild to moderate binding affinities as compared to the ligand. Thus, based on docking results and good binding scores observed with the HpIMPDH active site, an in-vitro HpIMPDH inhibition assay was done for the compounds. Citropten showed the most promising inhibitory activity with an IC50 value of 2.4 μM. Conclusion: The present study demonstrates that C. sinensis L. leaves are a good source for supplying coumarins that can act as naturally effective anti-H. pylori agents.

Treatment strategies and pharmacist-led medication management for Helicobacter pylori infection

Half of the world's population is Helicobacter pylori carrier. Updated guidelines and consensus have been issued across regions with the main aim of reducing social transmission and increasing H. pylori eradication rate. Although alternative therapies including traditional Chinese medicine and probiotics have also been used to improve H. pylori eradication rate in clinical practice, current mainstream treatment is still dependent on triple and quadruple therapies that includes antibacterial agents (e.g., amoxicillin and furazolidone) and proton pump inhibitor. Researches also assessed the eradication rate of optimized high-dose dual therapy in treating H. pylori infection. With the increase of antibiotic resistance rate, the treatment strategies for H. pylori infection are constantly adjusted and improved. Besides, low medication compliance is another key influencing factor for H. pylori treatment failure. Emerging studies indicate that pharmacists' intervention and new pharmaceutical care methods can enhance patient medication compliance, reduce adverse drug reactions, and improve H. pylori eradication rate. The purpose of this review is to summarize the advances in treating H. pylori infection and highlight the necessity of developing novel strategies to cope with the increasing challenges and to achieve personalized medication. Also, this review attaches great importance to pharmacists in optimizing H. pylori treatment outcomes as a routine part of therapy.

New pyrazole-tetrazole hybrid compounds as potent α-amylase and non-enzymatic glycation inhibitors

The synthesis of eight novel pyrazole-tetrazole compounds are presented. Their structures are identified by NMR and FTIR spectroscopy, mass spectrometry as well as elemental analysis. Their in-vitro α-amylase inhibition and haemoglobin antiglycation activity were examined by spectrophotometric methods. All compounds possess both activities, especially molecules entitled 2-(1-((5-methyl-1H-pyrazol-3-yl)methyl)-1H-tetrazol-5-yl)pyridine 4 and 2-(1-((1-ethyl-5-methyl-1H-pyrazol-3-yl)methyl)-1H-tetrazol-5-yl)pyridine 8 which were found to be extremely potent compared to the positive controls. The SAR study proved the influence of the alkylation position of pyrazole derivative on the tetrazole ring, the nature of substituent on the tetrazolic carbon atom and the nature of the group at the nitrogen atom of the pyrazole ring on both α-amylase and glycation inhibition activity. Compounds 4 and 8 could be a good drug candidate to treat Type 2 diabetes.

Chitosan Schiff bases-based polyelectrolyte complexes with graphene quantum dots and their prospective biomedical applications

Chitosan (Cs) bis-aldehyde Schiff base derivatives were synthesized by condensation of Cs with three bis-aldehydes namely; butane-1,4-diyl bis(4-formylbenzoate), N,N'-(butane-1,4-diyl)bis(2-(4-formylphenoxy)acetamide) and 4,4'-(butane-1,4-diylbis(oxy))dibenzaldehyde. The prepared Cs derivatives were blended with carboxymethyl chitosan(CMC) and graphene quantum dots (GQDs) to produce semi-IPNs polyelectrolyte complexes (PECs). and characterized with respect to their molecular structure and physio-chemical properties. The antibacterial activity against H. pylori (and in vitro Inosine 5'-monophosphate dehydrogenase IMPDH inhibitory assay) was evaluated. Additionally, a preliminary in vitro assessment for wound healing was performed against PECs in which wound closure percentages, and rates were investigated indicating an accelerated wound healing compared with untreated cells. The PEC based on Schiff base PEC containing amide linkage showed the highest wound healing ability. A minimal inhibitory concentration (MIC) was obtained for the PEC sample containing Cs Schiff base derived from 4,4'-(butane-1, 4-diylbis(oxy))dibenzaldehyde at a dose of 0.98 μg/ml inhibiting H. pylori growth by 100%. Additionally, the selected above-mentioned compound was selected to test its inhibitory activity against the HpIMPDH enzyme in addition to its selectivity towards the hIMPDH2 enzyme and was found to have promising activity against the HpIMPDH enzyme with IC₅₀ value of 0.65 μM, and to be safer and less active against the hIMPDH2 enzyme with IC₅₀ > 10 μM, reflecting its selectivity.

A recombinant scFv antibody-based fusion protein that targets EGFR associated with IMPDH2 downregulation and its drug conjugate show therapeutic efficacy against esophageal cancer

The present study aimed to evaluate the anti-tumor efficacy of the epidermal growth factor receptor (EGFR)-targeting recombinant fusion protein Fv-LDP-D3 and its antibody-drug conjugate Fv-LDP-D3-AE against esophageal cancer. Fv-LDP-D3, consisting of the fragment variable (Fv) of an anti-EGFR antibody, the apoprotein of lidamycin (LDP), and the third domain of human serum albumin (D3), exhibited a high binding affinity for EGFR-overexpressing esophageal cancer cells, inhibited EGFR phosphorylation and down-regulated inosine monophosphate dehydrogenase type II (IMPDH2) expression. Fv-LDP-D3 was taken up by cancer cells through intensive macropinocytosis; it inhibited the proliferation and induced the apoptosis of esophageal cancer cells. In vivo imaging revealed that Fv-LDP-D3 displayed specific tumor-site accumulation and a long-lasting retention over a 26-day period. Furthermore, Fv-LDP-D3-AE, a pertinent antibody-drug conjugate prepared by integrating the enediyne chromophore of lidamycin into the Fv-LDP-D3 molecule, displayed highly potent cytotoxicity, inhibited migration and invasion, induced apoptosis and DNA damage, arrested cells at G2/M phase, and caused mitochondrial damage in esophageal cancer cells. More importantly, both of Fv-LDP-D3 and Fv-LDP-D3-AE markedly inhibited the growth of esophageal cancer xenografts in athymic mice at well tolerated doses. The present results indicate that Fv-LDP-D3, and Fv-LDP-D3-AE exert prominent antitumor efficacy associated with targeting EGFR, suggesting their potential as promising candidates for targeted therapy against esophageal cancer.

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.

Development, synthesis, and biological evaluation of sulfonyl-α-l-amino acids as potential anti-Helicobacter pylori and IMPDH inhibitors

Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes a crucial step in the biosynthesis of DNA and RNA, and it has been exploited as a promising target for antimicrobial therapy. The present study discusses the development and synthesis of a series of sulfonyl-α-l-amino acids coupled with the anisamide scaffold and evaluates their activities as anti-Helicobacter pylori and IMPDH inhibitors. Twenty derivatives were synthesized and their structures were established by high-resolution mass spectrometry and ¹ H and ¹³ C nuclear magnetic resonance measurements. Four compounds (6, 10, 11, and 21) were found to be the most potent and selective molecules in the series with minimum inhibitory concentration (MIC) values <17 µM, which were selected to test their inhibitory activities against HpIMPDH and human (h)IMPDH2 enzymes. In all tests, amoxicillin and clarithromycin were used as reference drugs. Compounds 6 and 10 were found to have a promising activity against the HpIMPDH enzyme, with IC₅₀  = 2.42 and 2.56 µM, respectively. Moreover, the four compounds were found to be less active and safer against hIMPDH2 than the reference drugs, with IC₅₀  > 17.17 µM, which makes sure that their selectivity is toward HpIMPDH and reverse to that of amoxicillin and clarithromycin. Also, the synergistic antibacterial activity of compounds 6, 10, amoxicillin, and clarithromycin was investigated in vitro. The combination of amoxicillin/compound 6 (2:1 by weight) exhibited a significant antibacterial activity against H. pylori, with MIC = 0.12 µg/ml. The molecular docking study and ADMET analysis of the most active compounds were used to elucidate the mode-of-action mechanism.

Anxiolytic activity of Psidium guajava in mice subjected to chronic restraint stress and effect on neurotransmitters in brain

The anxiolytic activity of Psidium guajava L. leaf ethanolic extract (PLE) and its effect on neurotransmitter systems was investigated. PLE, extracted using Soxhlet apparatus, was subjected to preliminary qualitative and quantitative (flavonoids and phenols) analyses. The anxiolytic activity at 100, 200, and 400 mg/Kg doses were assessed in mice using elevated plus maze (EPM) and light/dark transition (LDT) test models on days 1 and 16. Neurotransmitters such as monoamines (serotonin, norepinephrine, and dopamine), γ-aminobutyric acid (GABA), and glutamate were estimated in different regions of the brain (cortex, hippocampus, and cerebellum and brain stem). Phytoconstituents identified using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry were analyzed in silico to evaluate their potential binding mode(s) to GABA_A and 5-HT_1A receptors. Phytochemical studies showed the presence of alkaloids, tannins, flavonoids, saponins, anthraquinone glycosides, carbohydrates, and proteins, whereas total flavonoid and phenol contents were estimated to be 64.96 ± 0.95 and 206.58 ± 1.60 mg/g of dried extract, respectively. PLE treatment significantly enhanced exploratory activity of mice in EPM and LDT models with significant effects on monoamines, GABA and glutamate levels in the brain. The in silico studies suggested the interaction(s) of PLE component(s) with GABA_A /5-HT_1A receptors as a potential mechanism of its anxiolytic activity.

A novel series of substituted 1,2,3-triazoles as cancer stem cell inhibitors: Synthesis and biological evaluation

An alarming increase in global death toll resulting from cancer incidents, particularly due to multidrug resistance and reduced efficacy as a consequence of target mutations, has compelled us to look for novel anticancer agents. Cancer stem cells (CSCs), contributing majorly to the chemoresistance and tumor relapse, seem to the main culprits. In the present investigation, new chemical entities (NCEs) belonging to four novel chemical series (A: 4'-allyl-2'-methoxyphenoxymethyl-1,2,3-triazoles; B: 4'-acetamidophenoxymethyl-1,2,3-triazoles; C: naphthalene-1'-yloxymethyl-1,2,3-triazoles, and D: naphthalene-2'-yloxymethyl-1,2,3-triazoles) were synthesized via Copper (I)-catalyzed alkyne-azide cycloaddition reaction and evaluated for in vitro anticancer activity. A total of 30 NCEs (39-68) were screened at 10 μM concentration in cell viability assay against cancer cell lines such as breast (MDA-MB-231), prostate (PC-3), glioma (U87 MG), along with cervical (SiHa) and lung (A549). The NCEs from Series C (56-60) and D (61-68) were more potent than those in Series A (39-45) and Series B (46-55) at the tested concentration. Furthermore, NCEs with >80% inhibition at 10 μM were evaluated for dose response. A total of five NCEs, 48, 56, 61, 65 and 66, were further assessed in soft-agar assay and found to be relatively potent (IC₅₀  < 10 μM). Finally, the hits were screened in sphere assay to identify potential CSC inhibitors against mammospheres (MDA-MB-231) and prostatospheres (PC-3). More so, the hits were also evaluated to understand in vitro cytotoxicity against normal cells using mouse embryonic fibroblast cell line (NIH/3T3) and human peripheral blood mononuclear cells (hPBMCs). Overall, hits 56 and 61 exhibited potent anticancer as well as CSC inhibitory activities with notably less toxicity toward NIH/3T3 and hPBMCs. On the whole, our arduous study led to the identification of potential hits with anticancer and CSC inhibitory activities, with minimal or no toxicity to normal cells.

Evaluation of Bronopol and Disulfiram as Potential Candidatus Liberibacter asiaticus Inosine 5'-Monophosphate Dehydrogenase Inhibitors by Using Molecular Docking and Enzyme Kinetic

Citrus huanglongbing (HLB) is a destructive disease that causes significant damage to many citrus producing areas worldwide. To date, no strategy against this disease has been established. Inosine 5'-monophosphate dehydrogenase (IMPDH) plays crucial roles in the de novo synthesis of guanine nucleotides. This enzyme is used as a potential target to treat bacterial infection. In this study, the crystal structure of a deletion mutant of CLas IMPDHΔ98-201 in the apo form was determined. Eight known bioactive compounds were used as ligands for molecular docking. The results showed that bronopol and disulfiram bound to CLas IMPDHΔ98-201 with high affinity. These compounds were tested for their inhibition against CLas IMPDHΔ98-201 activity. Bronopol and disulfiram showed high inhibition at nanomolar concentrations, and bronopol was found to be the most potent molecule (Ki = 234 nM). The Ki value of disulfiram was 616 nM. These results suggest that bronopol and disulfiram can be considered potential candidate agents for the development of CLas inhibitors.

Inhibitors of inosine 5'-monophosphate dehydrogenase as emerging new generation antimicrobial agents

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a vital enzyme involved in the de novo synthesis of guanine nucleotides. IMPDH catalyzes a crucial step of converting IMP into XMP that is further converted into GMP. Microbial infections rely on the rapid proliferation of bacteria, and this requires the rate-limiting enzyme IMPDH to expand the guanine nucleotide pool and hence, IMPDH has recently received lots of attention as a potential target for treating infections. Owing to the structural and kinetic differences in the host IMPDH and bacterial IMPDH, a selective targeting is possible and is a crucial feature in the development of new potent and selective inhibitors of bacterial IMPDH. Earlier screening of small molecules revealed a structural requirement for the bacterial/protozoal IMPDH. Early optimization of benzimidazole and benzoxazole scaffolds led to the discovery of new potent and selective inhibitors of pathogenic IMPDH. Further research is vastly focused on the development of highly potent and selective inhibitors of various bacterial IMPDHs. Such studies reveal the importance of this excellent target for treating infectious diseases. The current review focuses on the recent developments in the discovery and development of selective inhibitors of bacterial/protozoal IMPDH with emphasis on the inhibition mechanism and structure-activity relationship.