Inhibition of Helicobacter pylori and Its Associate Urease by Labdane Diterpenoids Isolated from Andrographis paniculata

Edible and herbal plants against Helicobacter pylori infection: From epidemiological, experimental studies to clinical perspectives

Helicobacter pylori (H. pylori) infection is an important global public health concern, causing conditions like gastritis, gastroduodenal ulcers, gastric lymphoma, distal gastric cancer and other gastric diseases. With the increasing prevalence of antibiotics resistance, the cure rate of antibiotics-based triple or quadruple therapy has declined to 80 % or less. Moreover, side effects still remain. Hence, alternative, more potent and safer anti-H. pylori medications are required. Numerous studies have indicated that natural products from medical plants are valuable repositories for the prevention of H. pylori infection with advantages in little side effects due to the co-evolution with biological systems for millions of years. In this review, we highlighted the anti-H. pylori activities and the responsive mechanism of edible and medical plants based on epidemiological, experimental, and clinical studies, providing the basis for future development of functional foods or drugs against H. pylori.

Identification of potential andrographolide-based drug candidate against Keap1-Nrf2 pathway through rigorous cheminformatics screening

The Keap1-Nrf2 [Kelch-like ECH-associated protein-1-Nuclear factor erythroid-2-related factor-2] regulatory pathway plays a vital role in the protection of cells by regulating transcription of antioxidant and detoxification genes. Andrographolide (AGP) regulates the Keap1-Nrf2 pathway by inhibiting the Keap1 protein. To identify a more potent AGP analog as a therapeutic agent against Keap1 protein, in this work, cheminformatics analysis of 237 AGP analogs was carried out. Amongst these, five AGP analogs were screened through virtual screening followed by their molecular docking analysis against Keap1 protein, which revealed greater binding affinities (binding energy =  - 4.15 to - 5.59 kcal/mol) for the shortlisted AGP analogs compared to AGP (binding energy =  - 4.02 kcal/mol). Pharmacophore mapping indicated 14 spatial features, including 3 hydrogen bond acceptors and 11 hydrophobic, while ADME analysis established the potential of all five analogs as orally-active drug-like candidates based on Lipinski's rule of five. We also examined the chemical reactivity of AGP and the shortlisted AGP analogs using DFT analysis, which revealed that except for one analog (AGP_A2) all are more chemically reactive than AGP. Further, molecular dynamics simulation analysis and MM/GBSA evidenced that AGP_A1 (PubchemID-123361152), AGP_A3 (PubchemID-58209855) and AGP_A4 (PubchemID-101362374) are the best drug like candidates compared to AGP and have greater potential to activate the Keap1-Nrf2 pathway by inhibiting the Keap1 protein.

Sanguinarine, a major alkaloid from Zanthoxylum nitidum (Roxb.) DC., inhibits urease of Helicobacter pylori and jack bean: Susceptibility and mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum nitidum (Roxb.) DC. (Z. nitidum) is a traditional Chinese medicine and mainly adopted to treat gastric ulcer, gastritis and stomach cancer. Sanguinarine (SNG), a natural alkaloid isolated from Z. nitidum, possesses significant anti-Helicobacter pylori and gastric protection effects. However, the underlying mechanism is sparsely elucidated.

AIM OF THIS STUDY

The present study aims to explore the inhibition effect, kinetics and potential mechanism of SNG against H. pylori urease (HPU) and jack bean urease (JBU).

MATERIALS AND METHODS

The improved spectrophotometric berthelot method was applied to estimate the inhibitory effect of SNG against HPU and JBU. The Lineweaver-Burk plots were adopted for investigating the inhibitory pattern in enzymatic kinetics. Sulfydryl-containing compounds and competitive active-site Ni²⁺ binding depressors were used for mechanism research.

RESULTS

SNG remarkably suppressed the activities of HPU and JBU in concentration-and time-dependent mode with IC₅₀ of 0.48 ± 0.14 mM and 0.11 ± 0.02 mM, respectively, in comparison with urease retardant acetohydroxamic acid (0.06 ± 0.01 mM for HPU and 0.03 ± 0.00 mM for JBU, respectively). Kinetic analysis demonstrated that the inhibition of SNG against HPU and JBU were separately characterized by slow-binding, mixed-type and slow-binding, non-competitive type. Addition of sulfydryl-containing reagents (dithiothreitol, glutathione and L-cysteine) and competitive Ni²⁺ binding restrainers (boric acid and sodium fluoride) significantly abrogated the urease inhibitory effect of SNG, suggesting the significant role of the thiols and Ni²⁺ for the urease inhibition by SNG. By contrast, interaction with thiol groups possibly contributed to the repression of SNG on JBU. Furthermore, the urease suppression was proved to be partially reversible since the SNG-blocked enzyme could be partly reactivated by glutathione.

CONCLUSION

SNG could observably inhibit H. pylori urease targeting the thiols and Ni²⁺, which indicated that SNG was a new urease suppressant with great promise. The present research also provided scientific evidence for the application of SNG and Z. nitidum treating H. pylori-associated gastrointestinal diseases.

Labdane-type Diterpenes from Pinus eldarica Needles and Their Anti-Helicobacter pylori Activity

Pinus eldarica is a medicinal tree used in traditional herbal medicine for the treatment of bronchial asthma and various skin diseases. As part of our ongoing search for bioactive phytochemicals with novel structures in natural products, we performed a phytochemical analysis of the methanol (MeOH) extract from P. eldarica needles collected in Iran. Phytochemical investigation of the MeOH extract, aided by liquid chromatography-mass spectrometry-based analysis, resulted in the isolation and identification of three labdane-type diterpenes (1-3), including a new and relatively unique norlabdane-type diterpene with a peroxide moiety, eldaricoxide A (1). The chemical structures of the isolated labdane-type diterpenes were elucidated by analyzing the spectroscopic data from 1D and 2D NMR and high-resolution electrospray ionization-mass spectrometry. The absolute configuration of eldaricoxide A (1) was established by employing a computational method, including electronic circular dichroism calculation and specific optical rotation. An anti-Helicobacter pylori test was conducted, where compound 3 exhibited the most potent antibacterial activity against H. pylori strain 51, inducing 72.7% inhibition (MIC₅₀ value of 92 μM), whereas eldaricoxide A (1) exhibited moderate antibacterial activity against H. pylori strain 51, inducing 54.5% inhibition (MIC₅₀ value of 95 μM). These findings demonstrated that the identified bioactive labdane-type diterpenes 1 and 3 can be applied in the development of novel antibiotics against H. pylori for the treatment of gastric and duodenal ulcers.

High-resolution liquid chromatography and mass spectrometry (HR-LCMS) assisted phytochemical profiling and an assessment of anticancer activities of Gracilaria foliifera and Turbinaria conoides using in vitro and molecular docking analysis

Marine algae's, owing to diverse range of secondary metabolites, opening up the new avenues in new drug development and can be used efficiently in anticancer research. Two seaweeds Gracilaria foliifera and Turbinaria conoides are subjected to phytochemical investigation by HR-LCMS and NMR which confirms presence of different bioactive compounds. The cytotoxicity of the dichloromethane (DCM) fraction of Gracilaria foliifera and Turbinaria conoides was determined using an in vitro methyl thiazolyl tetrazolium (MTT) test and showed considerable dose-dependent cytotoxicity on tumour cell lines. In MCF7, Gracilaria foliifera had an IC₅₀ of 100 μg/ml, while Turbinaria conoides had an IC₅₀ of 200 μg/ml and both the DCM fraction had IC₅₀ values of 100 μg/ml in the A549 cell line. MTT assay for anticancer activity suggest that Gracilaria foliifera has potent anticancer activity in both breast and lung cell lines, while the DCM fraction of Turbinaria conoides has potent activity in lung cell lines and moderate activity in breast cell lines. The anticancer effects of the discovered drugs targeting the most prevalent enzymes VEGFR and AXL tyrosine kinases were confirmed using a computational technique. We believe that residues from VEGFR, like Lys868, Asn923, Asp1046, and Phe1047 and Asp690 from Axl kinase may have contributed to the plausible anti-cancer benefit seen in this study. Communicated by Ramaswamy H. Sarma.

Advances in ameliorating inflammatory diseases and cancers by andrographolide: Pharmacokinetics, pharmacodynamics, and perspective

Andrographolide, a well-known natural lactone having a range of pharmacological actions in traditional Chinese medicine. It has long been used to cure a variety of ailments. In this review, we cover the pharmacokinetics and pharmacological activity of andrographolide which supports its further clinical application in cancers and inflammatory diseases. Growing evidence shows a good therapeutic effect in inflammatory diseases, including liver diseases, joint diseases, respiratory system diseases, nervous system diseases, heart diseases, inflammatory bowel diseases, and inflammatory skin diseases. As a result, the effects of andrographolide on immune cells and the processes that underpin them are discussed. The preclinical use of andrographolide to different organs in response to malignancies such as colorectal, liver, gastric, breast, prostate, lung, and oral cancers has also been reviewed. In addition, several clinical trials of andrographolide in inflammatory diseases and cancers have been summarized. This review highlights recent advances in ameliorating inflammatory diseases as well as cancers by andrographolide and its analogs, providing a new perspective for subsequent research of this traditional natural product.

Synthesis of New 3-Arylaminophthalides and 3-Indolyl-phthalides using Ammonium Chloride, Evaluation of their Anti-Mycobacterial Potential and Docking Study

OBJECTIVE

The study aims at the derivatization of "Phthalides" and synthesizes 3- arylaminophthalides & 3-indolyl-phthalides compounds, and evaluates their anti-tubercular and antioxidant activities. The study has also intended to employ the in silico methods for the identification of possible drug targets in Mycobacterium and evaluate the binding affinities of synthesized compounds.

METHODS

This report briefly explains the synthesis of phthalide derivatives using ammonium chloride. The synthesized compounds were characterized using spectral analysis. Resazurin Microtiter Assay (REMA) plate method was used to demonstrate the anti-mycobacterial activity of the synthesized compounds. An in-silico pharmacophore probing approach was used for target identification in Mycobacterium. The structural level interaction between the identified putative drug target and synthesized phthalides was studied using Lamarckian genetic algorithm-based software.

RESULTS AND DISCUSSION

In the present study, we report an effective, environmentally benign scheme for the synthesis of phthalide derivatives. Compounds 5c and 5d from the current series appear to possess good anti-mycobacterial activity. dCTP: deaminasedUTPase was identified as a putative drug target in Mycobacterium. The docking results clearly showed the interactive involvement of conserved residues of dCTP with the synthesized phthalide compounds.

CONCLUSION

On the eve of evolving anti-TB drug resistance, the data on anti-tubercular and allied activities of the compounds in the present study demonstrates the enormous significance of these newly synthesized derivatives as possible candidate leads in the development of novel anti-tubercular agents. The docking results from the current report provide a structural rationale for the promising anti-tubercular activity demonstrated by 3-arylaminophthalides and 3-indolyl-phthalides compounds.

Molecular Docking Simulations with ArgusLab

Molecular docking is the major computational technique employed in the early stages of computer-aided drug discovery. The availability of free software to carry out docking simulations of protein-ligand systems has allowed for an increasing number of studies using this technique. Among the available free docking programs, we discuss the use of ArgusLab ( http://www.arguslab.com/arguslab.com/ArgusLab.html ) for protein-ligand docking simulation. This easy-to-use computational tool makes use of a genetic algorithm as a search algorithm and a fast scoring function that allows users with minimal experience in the simulations of protein-ligand simulations to carry out docking simulations. In this chapter, we present a detailed tutorial to perform docking simulations using ArgusLab.

Coptisine-induced inhibition of Helicobacter pylori: elucidation of specific mechanisms by probing urease active site and its maturation process

In this study, we examined the anti-Helicobactor pylori effects of the main protoberberine-type alkaloids in Rhizoma Coptidis. Coptisine exerted varying antibacterial and bactericidal effects against three standard H. pylori strains and eleven clinical isolates, including four drug-resistant strains, with minimum inhibitory concentrations ranging from 25 to 50 μg/mL and minimal bactericidal concentrations ranging from 37.5 to 125 μg/mL. Coptisine’s anti-H. pylori effects derived from specific inhibition of urease in vivo. In vitro, coptisine inactivated urease in a concentration-dependent manner through slow-binding inhibition and involved binding to the urease active site sulfhydryl group. Coptisine inhibition of H. pylori urease (HPU) was mixed type, while inhibition of jack bean urease was non-competitive. Importantly, coptisine also inhibited HPU by binding to its nickel metallocentre. Besides, coptisine interfered with urease maturation by inhibiting activity of prototypical urease accessory protein UreG and formation of UreG dimers and by promoting dissociation of nickel from UreG dimers. These findings demonstrate that coptisine inhibits urease activity by targeting its active site and inhibiting its maturation, thereby effectively inhibiting H. pylori. Coptisine may thus be an effective anti-H. pylori agent.

Natural Products for the Prevention and Management of Helicobacter pylori Infection

Helicobacter pylori is the main pathogen that induces chronic gastritis, peptic ulcers, atrophic gastritis, and other gastric disorders, and it is classified as a group I carcinogen. To eradicate H. pylori infection, triple therapy consisting of two antibiotics and a proton pump inhibitor is the most widely recommended first-line therapeutic strategy. Antimicrobial resistance to antibiotics contained in triple therapy could lead to therapeutic regimen failures. Recent studies showed that many natural products, including fruits, vegetables, spices, and medicinal plants, possess inhibitory effects on H. pylori, indicating their potential to be alternatives to prevent and manage H. pylori infection. This review summarizes the effects of natural products on H. pylori infection and highlights the mechanisms of action.