Development of cannabidiol derivatives as potent broad-spectrum antibacterial agents with membrane-disruptive mechanism

Synthesis and anti-MRSA activity of quaternized small molecule antimicrobial peptide mimics based on norharmane

The escalating prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections, coupled with the diminishing efficacy of existing antimicrobial agents, has created an urgent need for novel antibacterial therapeutics. Here, three classes of quaternized small molecule antimicrobial peptide mimics (SMAPMs) incorporating norharmane skeleton were prepared based on molecular splicing strategy. Among them, compound 10c demonstrated excellent activity against MRSA, exhibiting a low minimum inhibitory concentration (MIC) of 0.25 μg/mL in vitro, coupled with significant therapeutic efficacy in a murine skin infection model in vivo. Additionally, compound 10c possessed rapid bactericidal property, low tendency to induce resistance, good plasma stability, and acceptable biosafety in vitro and in vivo. Mechanistic studies revealed that 10c exerts its multi-target antibacterial effects through several distinct pathways: (1) inhibition of biofilm formation; (2) cell wall disruption via interactions with peptidoglycan and lipoteichoic acids; (3) membrane targeting characterized by depolarization, altered permeability, and structural integrity loss; (4) reduction of metabolic activity; (5) disruption of cellular redox homeostasis; and (6) DNA binding. These findings demonstrate that compound 10c has the potential to be a candidate drug, while simultaneously providing a theoretical foundation for future anti-MRSA drug development through the SMAPMs strategy.

Total Synthesis of Auriculatin and Millexatin F and Discovery of Their Antibacterial Mechanism

The emergence of multidrug-resistant (MDR) bacteria necessitates the urgent development of novel antibacterial agents. This study reported the first total synthesis of two antibacterial isoflavones, auriculatin (1) and millexatin F (2), derived from the tropical medicinal plant Millettia extensa. Through in vitro evaluations, both compounds 1 and 2 possessed significant antibacterial activities (MICs = 0.5-4 μg/mL) and rapid bactericidal properties against Gram-positive bacteria, along with high safety for mammalian cells. Mechanistic studies revealed that auriculatin (1) and millexatin F (2) interact with bacterial cell membranes, inducing alterations in bacterial morphology and membrane permeability and inducing a rise in the leakage of intracellular DNA and proteins, thereby leading to bacterial death. In addition, our studies indicated that millexatin F (2) could interact with phosphatidylethanolamine (PE) and cardiolipin (CL) of cytoplasmic membranes in both Gram-positive and Gram-negative bacteria. Furthermore, millexatin F (2) showed increased efficacy against Gram-negative bacteria when combined with a permeabilizer (polymyxin B nonapeptide), indicating potential for broader application. These findings underscore the therapeutic promise of auriculatin (1) and millexatin F (2) as lead candidates in the fight against bacterial infections.

Unlocking the Antibacterial Potential of Naphthalimide-Coumarins to Overcome Drug Resistance with Antibiofilm and Membrane Disruption Ability against Escherichia coli

Resistance by bacteria to available antibiotics is a threat to human health, which demands the development of new antibacterial agents. Considering the prevailing conditions, we have developed a library of new naphthalimide-coumarin moieties as broad-spectrum antibacterial agents to fight against awful drug resistance. Preliminary studies indicate that compounds 8e and 8h display excellent antibacterial activity against Escherichia coli, exceeding the performance of marketed drug amoxicillin. These drug candidates effectively inhibit biofilm formation and disrupt the biofilm virulence factor, which is accountable for the formation of strong biofilm. In addition to this, both compounds exhibit fast bactericidal properties, thus shortening the time of treatment and resisting the emergence of drug resistance for up to 20 passages. Further, biofunctional evaluation reveals that both compounds effectively disrupt the membrane, causing the leakage of cytoplasmic contents and loss in metabolic activity. Both compounds 8e and 8h efficiently induce the ROS, leading to the oxidation of GSH to GSSG, decreasing the GSH activity of the cell, and causing oxidative damage to the cells. Additionally, both compounds effectively bind with DNA to block DNA replication and form supramolecular complexes, thus exhibiting antibacterial activity. Moreover, these compounds readily bind human serum albumin with high binding constants and can be transported to the target site easily. These findings reveal that newly synthesized naphthalimide-coumarin conjugates have the potential to build as potent antibacterial agents and can be used further for clinical trials.

Development of membrane-targeting chalcone derivatives as antibacterial agents against multidrug-resistant bacteria

The striking rise of infections caused by multidrug-resistant pathogens has evolved as a serious threat to public health worldwide. To develop new antibacterials to combat multidrug-resistant bacteria, a novel class of amphiphilic chalcone derivatives serving as antimicrobial peptidomimetics was designed and synthesized. Among them, the most promising compound 14b displayed broad-spectrum antimicrobial activity against both Gram-positive bacteria (MICs = 0.5-1 μg/mL) and Gram-negative bacteria (MICs = 1-32 μg/mL), low hemolytic activity, and good membrane selectivity. Moreover, compound 14b exhibited rapid bactericidal action, a low probability of developing resistance, high proteolytic stability, and strong capabilities of inhibiting and destroying bacterial biofilms. Further mechanism investigations revealed that compound 14b possessed strong membrane-disrupting abilities and could disintegrate the integrity of bacterial cell membranes by destroying transmembrane potential and enhancing membrane permeability, and causing the generation of intracellular ROS and the leakage of DNA and proteins, ultimately leading to bacterial death. More importantly, compound 14b also showed excellent in vivo therapeutic potency in a mouse septicemia model infected by both Gram-positive and Gram-negative bacteria, indicating its potential to be an antibacterial agent to confront bacterial infections.

Design, synthesis, and evaluation of pyranochromene derivatives as membrane targeting antibacterials against Gram-positive bacteria

The rapid growth of bacterial resistance has created obstacles for the effective treatment with conventional antibiotics, simultaneously posing a major threat to public health. In this study, a class of novel amphipathic pyranochromene derivatives were designed and synthesized by mimicking the amphiphilic characteristics of AMPs. Bioactivity screening identified a lead compound 5a with broad-spectrum antibacterial activity against Gram-positive stains (MICs = 1-4 μg/mL) and low hemolytic toxicity (HC50 = 111.6 μg/mL). Additionally, compound 5a displayed rapid bactericidal action, and was unlikely to induce bacterial resistance. Mechanistic investigation further demonstrated that compound 5a was able to disrupt the transmembrane potential and increased membrane permeability of S. aureus, which in turn causes leakage of cell contents such as DNA and proteins, ultimately leading to bacterial death. These findings indicated that compound 5a is a promising lead to combat bacterial infection caused by Gram-positive bacteria.

Development of amphipathic derivatives of thymol and carvacrol as potent broad-spectrum antibacterial agents

In the current study, to discover novel antibacterial agents, we designed and synthesized 72 carvacrol and thymol derivatives by biomimicking the structure and function of cationic antimicrobial peptides (AMPs). Many of the derivatives showed good antibacterial activity, and compound thy2I exhibited the most potent antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.5 μg/mL to 8 μg/mL. Compound thy2I could kill both gram-positive and gram-negative bacteria via a membrane-targeting mechanism of action with a low frequency of resistance. In addition, thy2I had the advantages of good membrane selectivity, low toxicity in vitro and in vivo, and good plasma stability. The in vivo activity results revealed that thy2I exhibited a positive therapeutic effect in a mouse skin abscess model induced by Staphylococcus aureus ATCC29213. After thy2I treatment (10 mg/kg), the bacterial load of the S. aureus-infected abscesses was reduced by approximately 99.65 %. Our study suggests that thy2I may serve as an antibacterial lead for further clinical evaluation.

Design, Synthesis, and Characterization of Novel Cannabidiol-Based Derivatives with Potent Antioxidant Activities

In recent years, extensive research has focused on cannabidiol (CBD), a well-studied non-psychoactive component of the plant-derived cannabinoids. CBD has shown significant therapeutic potential for treating various diseases and disorders, including antioxidants and anti-inflammatory effects. Due to the promising therapeutic effect of CBD in a wide variety of diseases, synthetic derivatization of this compound has attracted the attention of drug discovery in both industry and academia. In the current research, we focused on the derivatization of CBD by introducing Schiff base moieties, particularly (thio)-semicarbazide and aminoguanidine motifs, at the 3-position of the olivetolic ring. We have designed, synthesized, and characterized new derivatives based on CBD's framework, specifically aminoguanylhydrazone- and (thio)-semicarbazones-CBD-aldehyde compounds. Their antioxidant potential was assessed using FRAP and DPPH assays, alongside an evaluation of their effect on LDL oxidation induced by Cu2+ and AAPH. Our findings suggest that incorporating the thiosemicarbazide motif into the CBD framework produces a potent antioxidant, warranting further investigation.

Structure optimizing of flavonoids against both MRSA and VRE

Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) cause more than 100,000 deaths each year, which need efficient and non-resistant antibacterial agents. SAR analysis of 162 flavonoids from the plant in this paper suggested that lipophilic group at C-3 was crucial, and then 63 novel flavonoid derivatives were designed and total synthesized. Among them, the most promising K15 displayed potent bactericidal activity against clinically isolated MRSA and VRE (MICs = 0.25-1.00 μg/mL) with low toxicity and high membrane selectivity. Moreover, mechanism insights revealed that K15 avoided resistance by disrupting biofilm and targeting the membrane, while vancomycin caused 256 times resistance against MRSA, and ampicillin caused 16 times resistance against VRE by the same 20 generations inducing. K15 eliminated residual bacteria in mice skin MRSA-infected model (>99 %) and abdominal VRE-infected model (>92 %), which was superior to vancomycin and ampicillin.

Evaluation of novel compounds as anti-bacterial or anti-virulence agents

Antimicrobial resistance is a global threat, leading to an alarming increase in the prevalence of bacterial infections that can no longer be treated with available antibiotics. The World Health Organization estimates that by 2050 up to 10 million deaths per year could be associated with antimicrobial resistance, which would equal the annual number of cancer deaths worldwide. To overcome this emerging crisis, novel anti-bacterial compounds are urgently needed. There are two possible approaches in the fight against bacterial infections: a) targeting structures within bacterial cells, similar to existing antibiotics; and/or b) targeting virulence factors rather than bacterial growth. Here, for the first time, we provide a comprehensive overview of the key steps in the evaluation of potential new anti-bacterial and/or anti-virulence compounds. The methods described in this review include: a) in silico methods for the evaluation of novel compounds; b) anti-bacterial assays (MIC, MBC, Time-kill); b) anti-virulence assays (anti-biofilm, anti-quorum sensing, anti-adhesion); and c) evaluation of safety aspects (cytotoxicity assay and Ames test). Overall, we provide a detailed description of the methods that are an essential tool for chemists, computational chemists, microbiologists, and toxicologists in the evaluation of potential novel antimicrobial compounds. These methods are cost-effective and have high predictive value. They are widely used in preclinical studies to identify new molecular candidates, for further investigation in animal and human trials.