The development of thymol-isatin hybrids as broad-spectrum antibacterial agents with potent anti-MRSA activity

Bacterial resistance toward available therapeutic agents has become a nightmare for the healthcare system, causing significant mortality as well as prolonged hospitalization, thereby needing the urgent attention of research groups working on antimicrobial drug development worldwide. Molecular hybridization is a well-established tool for developing multifunctional compounds to tackle drug resistance. Inspired by the antibacterial profiles of isatin and thymol, along with the efficiency of a triazole linker in molecular hybridization, herein, we report the design, synthesis and antibacterial activity of a novel series of triazole tethered thymol-isatin hybrids. Most of the hybrids exhibited a broad-spectrum antibacterial efficacy against standard human pathogenic as well as clinically isolated multidrug-resistant bacterial strains listed in the WHO's 'priority pathogen' list and also in the ESKAPE group. Among them, hybrid compound AS8 was the most effective against methicillin-resistant Staphylococcus aureus (MIC = 1.9 μM and MBC = 3.9 μM), exhibiting biofilm inhibitory potential. AS8 exhibited dehydrosqualene synthase (CrtM) inhibitory potential in MRSA and decreased the production of virulence factor staphyloxanthin, which is one of the key mechanisms of its anti-MRSA efficacy, which was further supported by molecular docking and simulation studies. Moreover, AS8 was found to be non-toxic and showed a potent in vivo antibacterial efficacy (90% survival at 10 mg kg-1) as well as a modulated immune response in the larva-based (Galleria mellonella) model of systemic infections. Overall findings confirmed that AS8 can be a promising candidate or take the lead in the treatment and further drug development against drug-resistant infectious diseases, especially against MRSA infections.

Comprehensive computational investigation for ligand recognition and binding dynamics of SdiA: a degenerate LuxR -type receptor in Klebsiella pneumoniae

SdiA is a LuxR-type receptor that controls the virulence of Klebsiella pneumoniae, a Gram-negative bacterium that causes various infections in humans. SdiA senses exogenous acyl-homoserine lactones (AHLs) and autoinducer-2 (AI-2), two types of quorum sensing signals produced by other bacterial species. However, the molecular details of how SdiA recognizes and binds to different ligands and how this affects its function and regulation in K. pneumoniae still need to be better understood. This study uses computational methods to explore the protein-ligand binding dynamics of SdiA with 11 AHLs and 2 AI-2 ligands. The 3D structure of SdiA was predicted through homology modeling, followed by molecular docking with AHLs and AI-2 ligands. Binding affinities were quantified using MM-GBSA, and complex stability was assessed via Molecular Dynamics (MD) simulations. Results demonstrated that SdiA in Klebsiella pneumoniae exhibits a degenerate binding nature, capable of interacting with multiple AHLs and AI-2. Specific ligands, namely C10-HSL, C8-HSL, 3-oxo-C8-HSL, and 3-oxo-C10-HSL, were found to have high binding affinities and formed critical hydrogen bonds with key amino acid residues of SdiA. This finding aligns with the observed preference of SdiA for AHLs having 8 to 10 carbon-length acyl chains and lacking hydroxyl groups. In contrast, THMF and HMF demonstrated poor binding properties. Furthermore, AI-2 exhibited a low affinity, corroborating the inference that SdiA is not the primary receptor for AI-2 in K. pneumoniae. These findings provide insights into the protein-ligand binding dynamics of SdiA and its role in quorum sensing and virulence of K. pneumoniae.

Discovery of triazole tethered thymol/carvacrol-coumarin hybrids as new class of α-glucosidase inhibitors with potent in vivo antihyperglycemic activities

Keeping in view the inhibitory potential of monoterpenes thymol and carvacrol as well as coumarin nucleus against α-glucosidase, novel series of thymol/carvacrol-coumarin hybrids was designed, synthesized and evaluated for α-glucosidase inhibitory potential. Among the series of hybrid molecules, AS14 with IC50 value of 4.32 ± 0.11 μM was selective α-glucosidase inhibitor over α-amylase (IC50 = 37.36 ± 0.84 μM). AS14 was non-toxic toward mouse normal fibroblast cells (L929: IC50 > 100 μM). Molecular docking and dynamic simulation studies confirmed desired interactions of AS14 with α-glucosidase responsible for the inhibition of its catalysis capabilities. Acute oral toxicity study confirmed AS14 as safer molecule for in vivo pharmacological investigations with LD50 value of 300 mg/kg. AS14 also showed acute hypoglycaemic effects [reduction in blood glucose levels at 1 h of administration in maltose loading test (at 10 and 20 mg/kg by 62.65 % and 70.12 %) and sucrose loading test (at 10 and 20 mg/kg by 59.65 % and 60.23 %), respectively] as well as long term (28 days) fasting blood glucose reduction (At day 28: 10 mg/kg = 54.69 % and 20 mg/kg = 62.23 % reduction in fasting blood glucose levels) capabilities in streptozotocin induced diabetic rats. Overall study represents, AS14 as potential α-glucosidase inhibitor with adequate efficacy and safety profile and act as an effective hit lead for the further development of potent and safer α-glucosidase inhibitors for the management of postprandial hyperglycemia in diabetic patients.

Pinpointing top inhibitors for GSK3β from pool of indirubin derivatives using rigorous computational workflow and their validation using molecular dynamics (MD) simulations

Glycogen synthase kinase-3β (GSK3β) is a pivotal protein kinase implicated in a spectrum of debilitating diseases, encompassing cancer, diabetes, and neurodegenerative disorders. While the therapeutic potential of GSK3β inhibition is widely recognized, there remains an unmet need for a rigorous, systematic analysis probing the theoretical inhibition dynamics of a comprehensive library of indirubin derivatives against GSK3β using advanced computational methodologies. Addressing this gap, this study embarked on an ambitious endeavor, leveraging indirubin-a renowned scaffold-as a template to curate a vast library of 1000 indirubin derivatives from PubChem. These were enriched with varied substitutions and modifications, identified via a structure similarity search with a Tanimoto similarity threshold of 85%. Harnessing a robust virtual screening workflow, we meticulously identified the top 10 contenders based on XP docking scores. Delving deeper, we gauged the binding free energy differentials (ΔGBind) of these hits, spotlighting the top three compounds that showcased unparalleled binding prowess. A comparative pharmacophore feature mapping with the reference inhibitor OH8, co-crystallized with GSK3β (PDB ID: 6Y9R), was undertaken. The binding dynamics of these elite compounds were further corroborated with 100 ns molecular dynamics simulations, underlining their stable and potent interactions with GSK3β. Remarkably, our findings unveil that these indirubin derivatives not only match but, in certain scenarios, surpass the binding affinity and specificity of OH8. By bridging this research chasm, our study amplifies the therapeutic promise of indirubin derivatives, positioning them as frontrunners in the quest for groundbreaking GSK3β inhibitors, potentially revolutionizing treatments for a myriad of ailments.

A Comprehensive in vitro and in silico Assessment on Inhibition of CYP51B and Ergosterol Biosynthesis by Eugenol in Rhizopus oryzae

Mucormycosis, also known as Zygomycosis, is a disease caused by invasive fungi, predominantly Rhizopus species belonging to the Order of Mucorales. Seeing from the chemistry perspective, heterocyclic compounds with an "azole" moiety are widely employed as antifungal agent for minimising the effect of mucormycosis as a prescribed treatment. These azoles serve as non-competitive inhibitors of fungal CYP51B by predominantly binding to its heme moiety, rendering its inhibition. However, long-term usage and abuse of azoles as antifungal medicines has resulted in drug resistance among certain fungal pathogens. Hence, there is an unmet need to find alternative therapeutic compounds. In present study, we used various in vitro tests to investigate the antifungal activity of eugenol against R. oryzae/R. arrhizus, including ergosterol quantification to test inhibition of ergosterol production mediated antifungal action. The minimum inhibitory concentration (MIC) value obtained for eugenol was 512 μg/ml with reduced ergosterol concentration of 77.11 ± 3.25% at MIC/2 concentration. Further, the molecular interactions of eugenol with fungal CYP51B were meticulously studied making use of proteomics in silico study including molecular docking and molecular dynamics simulations that showed eugenol to be strongly interacting with heme in an identical fashion to that shown by azole drugs (in this case, clotrimazole was evaluated). This is the first of a kind study showing the simulation study of eugenol with CYP51B of fungi. This inhibition results in ergosterol synthesis and is also studied and compared with keeping clotrimazole as a reference.

Potential dual inhibition of SE and CYP51 by eugenol conferring inhibition of Candida albicans: Computationally curated study with experimental validation

Ergosterol is the key sterol component in the cell membrane of fungi including moulds and yeasts. Any decrease in the levels of ergosterol in the cell membrane of fungi render them venerable to cell membrane damage and even its death. Majority of antifungal drug targets the key enzymes involved in ergosterol biosynthesis pathway. The biochemical pathway for the synthesis of Ergosterol is a complex one, though the reactions carried by Squalene Epoxidase (SE) and 14α-demethylase (CYP51- a member of Cytochrome P450 family) serves to the key rate limiting reactions that can impact the overall production of Ergosterol. Allylamines class of antifungal drug target SE while Azoles target the CYP51. Currently advancement in the drug development is focused to introduce newer drugs that can simultaneously inhibit both this rate limiting enzymes. However, natural compounds established to possess antifungal activity but the major loophole about their understanding lies in the fact that their mode of action are severely unstudied. One such well-established antifungal natural phytochemical is Eugenol, and in current manuscript we investigated its efficacy to interact with both, SE and CYP51 of Candida albicans using molecular Docking, Free energy change calculations and Molecular Dynamics (MD) simulation, showing promising outcomes. For experimental studies, terbinafine, clotrimazole and eugenol showed 4 μg/ml, 2 μg/ml, and 512 μg/ml MIC₉₀ values, respectively against C. albicans and also showed reduction in Ergosterol production at sub-MIC levels. The obtained result indicates the involvement of eugenol in the inhibition of enzymes require in the ergosterol biosynthesis pathway.

Unravelling the antifungal mode of action of curcumin by potential inhibition of CYP51B: A computational study validated in vitro on mucormycosis agent, Rhizopus oryzae

Like human, fungi too are known to share lot of structural similarities amongst their CYPs (Cytochrome P450 super family of enzymes) which allows antifungal 'azole' compounds to interact with CYPs of human. Clotrimazole, an 'azole' antifungal drug, is a known inhibitor of fungal CYP named CYP51B. Curcumin, a phytochemical obtained from Curcuma longa has the ability to interact with several different human CYPs to induce inhibition. The sequence and the structural similarities amongst both human and fungal CYPs suggest a strong possibility for curcumin to interact with fungal CYP51B to behave like an antifungal agent. To test this hypothesis a study was designed involving mucormycosis agent, Rhizopus oryzae. The ability of curcumin to interact with fungal CYP51B was analysed computationally through molecular docking, MM-GBSA and Molecular Dynamics (MD) simulation assessment. Further, interaction profile for fungal CYP51B-curcumin was compared with human CYP3A4-curcumin, as there are published evidence describing curcumin as an inhibitor of human CYPs. Additionally, to validate in silico findings, an in vitro assay was performed to examine the antifungal potentials of curcumin on the R. oryzae. Conclusive results allow us to determine a plausible mode of action of curcumin to act as an antifungal against a mucormycosis agent.

Repurposing the antibacterial drugs for inhibition of SARS-CoV2-PLpro using molecular docking, MD simulation and binding energy calculation

Papain-like protease (nsp-3; non-structural protein) of novel corona virus is an ideal target for developing drugs as it plays multiple important functions for viral growth and replication. For instance, role of nsp-3 has been recognized in cleavage of viral polyprotein; furthermore, in infected host it weakens the immune system via downregulating the production of type I interferon. This downregulation is promoted by removal of ubiquitin-like interferon-stimulated gene 15 protein (ISG15) from interferon-responsive factor 3 (IRF3) protein. Among known inhibitors of SARS-CoV-PLpro GRL0617 is by far the most effective inhibitor. As PLpro of SARS-CoV2 is having more than 80% similarity with SARS-CoV-PLpro, GRL0617 is reported to be effective even against SARS-CoV2. Owing to this similarity, certain key amino acids remain the same/conserved in both proteins. Among conserved amino acids Tyr268 for SARS-CoV2 and Tyr269 for SARS-CoV produce important hydrophobic interactions with aromatic rings of GRL0617. Here, in this study antibacterial compounds were collected from ZINC database, and they were filtered to select compounds that are having similar structural features as GRL0617. This filtered library of compound was then docked with SARS-CoV and CoV2-PLpro. Five hits were noted that were able to interact with Tyr268 (SARS-CoV2) and Tyr269 (SARS-CoV). Further, best hit 2-(2-((benzofuran-2-carboxamido)methyl)-5-methoxy-1H-indol-1-yl)acetic acid (ZINC44459905) was studied using molecular dynamic simulation where stability of protein–ligand complex as well as stability of produced interactions was noted.

Endophytic fungi: A treasure trove of novel anticancer compounds

Cancer is a multifactorial disease with a convoluted genesis and progression. The emergence of multidrug resistance to presently be offered drug and relapse is by far, the most critical concern to tackle this deteriorating disease. Henceforth, there is undeniably an inflated necessity for safe, promising, and less harmful new anticancer drugs. Natural compounds from various sources like plants, animals, and microorganisms have occupied a center stage in drug discovery due to their tremendous chemical diversity and potential as therapeutic agents. Endophytic microbes are symbiotically associated with plants and have been proven to produce novel or analogues of host bioactive metabolites exhibiting a variety of biological activities including anticancer activity. This review emphasizes on structurally diverse unprecedented anticancer natural compounds that have been reported exclusively from endophytic fungi from 2016 to 2020. It covers chemical nature of metabolites, its fungal source associated with terrestrial, as well as marine plants and anticancer activity based on their cytotoxicity profile against various cancer cell lines. Many of these fungal metabolites with promising anticancer activity can be used as lead molecules for in silico experiments and deserve special attention from scientists for further in vitro and clinical research.

Stroke in Young-Dilative Arteriopathy: A Clue to Late-Onset Pompe's Disease?

IMPORTANCE

In almost a third of stroke in young cases, etiology remains unclear. We report a radiological entity which might give a clue toward detection of late onset Pompe's disease in some cases.

OBSERVATION

Here we report two cases of stroke in young in which evaluation led to diagnosis of late onset Pompe's disease. Both patients presented with recurrent stroke. On evaluation, one of them was found to have slowly progressive predominantly proximal quadriparesis. His muscle biopsy showed Pompe's disease and had dolichoectasia of posterior circulation vessels. The other patient did not have any muscle weakness. Detailed workup for stroke in young was negative, but as angiogram showed intracranial vessel dolichoectasia, he was also investigated and found to have Pompe's disease.

CONCLUSIONS AND RELEVANCE

We conclude that dolichoectasia of intracranial vessels in cases with stroke in young, with or without muscle weakness, should raise a differential of late onset Pompe's disease. This being one of the few treatable disorders makes the diagnosis all the more important.

Novel Starters for Value Added Fermented Dairy Products

Starter cultures are those microorganisms (bacteria, yeasts, and molds or their combinations) that initiate and carry out the desired fermentation essential in manufacturing cheese and fermented dairy products such as Dahi, Lassi, Yogurt, Sour cream, Kefir, and Koumiss amongst others. Starter culture is defined as “an active microbial preparation, deliberately added to initiate desirable changes during preparation of fermented products”. Starter cultures have a multifunctional role in dairy fermentations. The production of lactic acid by fermenting lactose is the major role of dairy starters. The acid is responsible for development of characteristic body and texture of the fermented milk products, contributes to the overall flavour of the products, and enhances preservation. Beyond the horizons of their conventional role in acid, flavour and texture development, they are being looked up on as burgeoning “cell factories” for production of host of functional biomolecules and food ingredients such as biothickeners, bacteriocins, vitamins, bioactive peptides and amino acids.

Early vascular healing with biodegradable polymer coated sirolimus-eluting coronary stent implantation: assessed by optical coherence tomography results at 4-month follow-up

AIM

The aim of this study was to evaluate the strut apposition and neointimal coverage of Supralimus-Core stent struts at 4 months after implantation using optical coherence tomography (OCT).

METHODS

The Supralimus-Core OCT study is a retrospective, single-center study evaluating strut apposition and neointimal coverage with OCT at 4 months after stent implantation. A total of 12 patients, who had 15 stents implanted were included in the study. The OCT was obtained using a C7-XR FD-OCT (frequency-domain OCT) intravascular imaging system. Strut apposition, neointimal hyperplasia (NIH) thickness and stent coverage on each stent strut were evaluated.

RESULTS

A total of 2870 struts and 1950 frames were analyzed from 15 stents. Average stent length was 29.3 mm. Average reference vessel diameter was 2.64 mm. Among 12 patients, 3 (25.0%) patients were with diabetes, 4 (26.7%) type B2 and 10 (66.7%) type C lesions. The apposed and covered struts were 2787 (97.11%), whereas malapposed and covered struts were 3 (0.10%), apposed and uncovered 49 (1.71%) and malapposed and uncovered 31 (1.08%). Mean NIH thickness was 155.1±55.2 µm.

CONCLUSION

The present study suggests that Supralimus-Core stent has a favorable vascular healing pattern at 4 months after stent implantation in terms of stent-strut coverage and strut apposition. This information indicates that the Supralimus-Core stent is a promising solution for decreasing late stent restenosis and preventing stent thrombosis.