Discovery of Sortase A covalent inhibitors with benzofuranene cyanide structures as potential antibacterial agents against Staphylococcus aureus

The Complete Assessment of Small Molecule and Peptidomimetic Inhibitors of Sortase A Towards Antivirulence Treatment

This review covers the most recent advances in the development of inhibitors for the bacterial enzyme sortase A (SrtA). Sortase A (SrtA) is a critical virulence factor, present ubiquitously in Gram-positive bacteria of which many are pathogenic. Sortases are key enzymes regulating bacterial adherence to host cells, by anchoring extracellular matrix-binding proteins to the bacterial outer cell wall. By targeting virulence factors, effective treatment can be achieved, without inducing antibiotic resistance to the treatment. This is a potentially more sustainable, long-term approach to treating bacterial infections, including ones that display multiple resistance to current therapeutics. There are many promising approaches available for SrtA inhibition, some of which have the potential to advance into further clinical development, with peptidomimetic and in vivo active small molecules being among the most promising. There are currently no approved drugs on the market targeting SrtA, despite its promise, adding to the relevance of this review article, as it extends to the pharmaceutical industry additionally to academic researchers.

Design, Synthesis, Antibacterial Activity, and Mechanisms of Novel Benzofuran Derivatives Containing Disulfide Moieties

The unsatisfactory effects of conventional bactericides and antimicrobial resistance have increased the challenges in managing plant diseases caused by bacterial pests. Here, we report the successful design and synthesis of benzofuran derivatives using benzofuran as the core skeleton and splicing the disulfide moieties commonly seen in natural substances with antibacterial properties. Most of our developed benzofurans displayed remarkable antibacterial activities to frequently encountered pathogens, including Xanthomonas oryzae pv oryzae (Xoo), Xanthomonas oryzae pv oryzicola (Xoc), and Xanthomonas axonopodis pv citri (Xac). With the assistance of the three-dimensional quantitative constitutive relationship (3D-QSAR) model, the optimal compound V40 was obtained, which has better in vitro antibacterial activity with EC50 values of 0.28, 0.56, and 10.43 μg/mL against Xoo, Xoc, and Xac, respectively, than those of positive control, TC (66.41, 78.49, and 120.36 μg/mL) and allicin (8.40, 28.22, and 88.04 μg/mL). Combining the results of proteomic analysis and enzyme activity assay allows the antibacterial mechanism of V40 to be preliminarily revealed, suggesting its potential as a versatile bactericide in combating bacterial pests in the future.

Structure-Guided Design, Synthesis, and Antivirulence Assessment of Covalent Staphylococcus aureus Sortase A Inhibitors

Sortase A (SrtA) is a membrane-associated cysteine transpeptidase required for bacterial virulence regulation and anchors surface proteins to cell wall, thereby assisting biofilm formation. SrtA is targeted in antivirulence treatments against Gram-positive bacterial infections. However, the development of potent small-molecule SrtA inhibitors is constrained owing to the limited understanding of the mode of action of inhibitors in the SrtA binding pocket. Herein, we designed and synthesized a novel class of covalent SrtA inhibitors based on the binding mode detailed in the X-ray crystal structure of the ML346/Streptococcus pyogenes SrtA complex. ML346 analog Y40 exhibited 2-fold increased inhibitory activity on Staphylococcus aureus SrtA and showed superior inhibitory effects on biofilm formation in vitro. Y40 protected Galleria mellonella larvae fromS. aureusinfections in vivo while minimally attenuating staphylococcal growth in vitro. Our study indicates that the covalent SrtA inhibitor Y40 is an antivirulence agent that is effective againstS. aureusinfections.

Synthesis and Biological Studies of Benzo[b]furan Derivatives: A Review from 2011 to 2022

The importance of the benzo[b]furan motif becomes evident in the remarkable results of numerous biological investigations, establishing its potential as a robust therapeutic option. This review presents an overview of the synthesis of and exhaustive biological studies conducted on benzo[b]furan derivatives from 2011 to 2022, accentuating their exceptional promise as anticancer, antibacterial, and antifungal agents. Initially, the discussion focuses on chemical synthesis, molecular docking simulations, and both in vitro and in vivo studies. Additionally, we provide an analysis of the intricate interplay between structure and activity, thereby facilitating comparisons and profoundly emphasizing the applications of the benzo[b]furan motif within the realms of drug discovery and medicinal chemistry.

Ephedra foeminea as a Novel Source of Antimicrobial and Anti-Biofilm Compounds to Fight Multidrug Resistance Phenotype

Plants are considered a wealthy resource of novel natural drugs effective in the treatment of multidrug-resistant infections. Here, a bioguided purification of Ephedra foeminea extracts was performed to identify bioactive compounds. The determination of antimicrobial properties was achieved by broth microdilution assays to evaluate minimal inhibitory concentration (MIC) values and by crystal violet staining and confocal laser scanning microscopy analyses (CLSM) to investigate the antibiofilm capacity of the isolated compounds. Assays were performed on a panel of three gram-positive and three gram-negative bacterial strains. Six compounds were isolated from E. foeminea extracts for the first time. They were identified by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) analyses as the well-known monoterpenoid phenols carvacrol and thymol and as four acylated kaempferol glycosides. Among them, the compound kaempferol-3-O-α-L-(2″,4″-di-E-p-coumaroyl)-rhamnopyranoside was found to be endowed with strong antibacterial properties and significant antibiofilm activity against S. aureus bacterial strains. Moreover, molecular docking studies on this compound suggested that the antibacterial activity of the tested ligand against S. aureus strains might be correlated to the inhibition of Sortase A and/or of tyrosyl tRNA synthase. Collectively, the results achieved open interesting perspectives to kaempferol-3-O-α-L-(2″,4″-di-E-p-coumaroyl)-rhamnopyranoside applicability in different fields, such as biomedical applications and biotechnological purposes such as food preservation and active packaging.

Benzofuran as a promising scaffold for the synthesis of novel antimicrobial agents

INTRODUCTION

The benzofuran moiety constitutes a main component of enormous biologically active natural and synthetic heterocycles. Such heterocycles have distinctive therapeutic potential and are employed in various clinical drugs. A number of publications have dealt with the synthesis and extraction of benzofuran-based heterocycles to investigate their antimicrobial potential.

AREAS COVERED

This review describes the antimicrobial activity of various natural and synthetic benzofuran scaffolds. The antimicrobial activity of benzofurans is thoroughly investigated against several bacterial (Gram-positive and Gram-negative) and fungal microorganisms compared with several reference antibiotic drugs. The effects of the electronic nature of substituents on the activity of benzofurans through SAR study were reported. This article also highlights the recent natural and synthetic benzofuran-based organic molecules between 2019-2022 that have had success in terms of their antimicrobial activity.

EXPERT OPINION

Many of the described benzofurans are promising candidates as antimicrobial agents based on their activity. Most used antibiotics target infections caused by the gram-positive pathogen S. aureus. Interestingly, most of the described benzofurans are promising inhibitors against S. aureus with either equipotent or more potent activity than the reference antibiotic drugs. These findings will encourage medicinal chemists to explore these new avenues for human health promotion to reduce suffering.

Natural aloe emodin-hybridized sulfonamide aminophosphates as novel potential membrane-perturbing and DNA-intercalating agents against Enterococcus faecalis

The dramatic rise in drug resistance accelerated the desire for new antibacterial agents to safeguard human health. This work constructed a novel type of aloe emodin-hybridized sulfonamide aminophosphates as unique potential antibacterial agents. The biological assay revealed that some target hybrids possessed potent inhibitory activity. Particularly, ethyl aminophosphate-hybridized sulfadiazine aloe emodin 7a (EASA-7a) not only displayed preponderant antibacterial efficiency against drug-resistant E. faecalis at low concentration as 0.25 μg/mL but also possessed strong bacteriostatic capacity and low propensity to develop resistance toward E. faecalis. The weak hemolysis toward human red blood cells and efficient biofilm-disruptive ability further implied the therapeutic potential of EASA-7a. Preliminary studies disclosed that the excellent antibacterial behavior of EASA-7a might be attributed to its capacity to permeate and depolarize the bacterial membrane, as well as promote ROS accumulation and intercalate with DNA. These findings manifested that EASA-7a was worthy of further development to combat life-threatening bacterial infections.