Broad-spectrum Activity Research Articles

Antibacterial Activity of AXOTL-13, a Novel Peptide Identified from the Transcriptome of the Salamander Ambystoma mexicanum

Background/Objectives: Antimicrobial peptides are essential molecules in the innate immunity of various organisms and possess a broad spectrum of antimicrobial, antitumor, and immunomodulatory activities. Due to their multifunctionality, they are seen as an alternative for controlling bacterial infections. Although conventional antibiotics have improved health worldwide, their indiscriminate use has led to the emergence of resistant microorganisms. To discover new molecules with antimicrobial activity that could overcome the limitations of traditional antibiotics, this study aimed to identify antimicrobial peptides in Ambystoma mexicanum. Methods: In this study, hypothetical proteins encoded in the Ambystoma mexicanum transcriptome were predicted. These proteins were aligned with peptides reported in the Antimicrobial Peptide Database (APD3) using the Fasta36 program. After identifying peptide sequences with potential antibacterial activity, their expression was confirmed through conventional polymerase chain reaction (PCR) and then chemically synthesized. The antibacterial activity of the synthesized peptides was evaluated against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922. Results: A new antimicrobial peptide named AXOTL-13 was identified. AXOTL-13 is an amphipathic cationic alpha-helical peptide with the ability to inhibit the growth of Escherichia coli without causing hemolysis in red blood cells, with its action likely directed at the membrane, as suggested by morphological changes observed through scanning electron microscopy. Conclusions: This research is pioneering in evaluating the activity of antimicrobial peptides present in Ambystoma mexicanum and in specifically identifying one of these peptides. The findings will serve as a reference for future research in this field.

Investigation of the Mechanism of Action of AMPs from Amphibians to Identify Bacterial Protein Targets for Therapeutic Applications

Antimicrobial peptides (AMPs) from amphibians represent a promising source of novel antibacterial agents due to their potent and broad-spectrum antimicrobial activity, which positions them as valid alternatives to conventional antibiotics. This review provides a comprehensive analysis of the mechanisms through which amphibian-derived AMPs exert their effects against bacterial pathogens. We focus on the identification of bacterial protein targets implicated in the action of these peptides and on biological processes altered by the effect of AMPs. By examining recent advances in countering multidrug-resistant bacteria through multi-omics approaches, we elucidate how AMPs interact with bacterial membranes, enter bacterial cells, and target a specific protein. We discuss the implications of these interactions in developing targeted therapies and overcoming antibiotic resistance (ABR). This review aims to integrate the current knowledge on AMPs’ mechanisms, identify gaps in our understanding, and propose future directions for research to harness amphibian AMPs in clinical applications.

Randomized Clinical Trials Demonstrate the Safety Assessment of Alkalihalobacillus clausii AO1125 for Use as a Probiotic in Humans

(1) Background: Alkalihalobacillus clausii AO1125 is a Gram-positive, motile, spore-forming bacterium with potential as a probiotic due to its broad-spectrum antimicrobial activity, inhibiting pathogens like Listeria monocytogenes, Staphylococcus aureus, and Clostridium difficile, as well as anti-rotavirus activity. Its resilience in gastrointestinal conditions suggests benefits for gut health. This study evaluates the safety and probiotic potential of A. clausii AO1125. (2) Methods: Genome annotation identified genes linked to probiotic traits such as stress resistance, gut colonization, immune modulation, and antimicrobial production. The genome was screened for antibiotic resistance genes using CARD, bacteriocin clusters using BAGEL4, and virulence factors via VFDB. Cytotoxicity was assessed on Vero cells and erythrocytes, and a Phase I, double-blind, placebo-controlled clinical trial was conducted with 99 healthy volunteers (50 AO1125, 49 placebo). (3) Results: Genomic analysis confirmed minimal antibiotic resistance genes and the absence of virulence factors, supporting safety. A. clausii AO1125 showed no pathogenicity, cytotoxicity, or hemolytic activity and was well-tolerated in clinical settings, with mild, transient abdominal gas as the most common adverse event. (4) Conclusions: The safety profile and genetic basis for probiotic and antimicrobial properties support A. clausii AO1125 as a promising probiotic candidate for gastrointestinal health, warranting further clinical research.

Assessment of therapeutic response to photodynamic therapy with the Zn-Phthalocyanine RLP068/Cl versus topical Clindamycin in patients affected by Hidradenitis Suppurativa: a comparative clinical pilot study

AbstractHidradenitis suppurativa is a chronic skin disorder characterized by painful inflammatory nodules and abscesses, significantly impacting patients’ quality of life. Current treatment strategies, including topical antibiotics, often yield limited efficacy and pose risks of antibiotic resistance. Photodynamic therapy has emerged as a potential option, with RLP068/Cl (ELKOFAST®, non-sterile formulation) showing promising efficacy due to its broad-spectrum bactericidal activity. We conducted a pilot study assessing the therapeutic response to photodynamic therapy with RLP068/Cl versus topical clindamycin gel in patients affected by hidradenitis suppurativa of Hurley score I, II, and III. Results revealed higher efficacy of photodynamic therapy in combination with RLP068/Cl, particularly in mild cases. Its efficacy remains reliable even in more severe cases when combined with adalimumab. The observed faster lesion improvement and pain relief were ascribed to the bactericidal effects of RLP068/Cl against Gram+ and Gram− bacteria. Furthermore, photoactivated RLP068/Cl was well tolerated with no adverse events reported. Therefore, photodynamic therapy following RLP068/Cl application represents a novel therapeutic option for hidradenitis suppurativa with potential implications for antibiotic stewardship in dermatology. Graphical abstract

In vitro skin permeation of flavonoid esters enzymatically derived from natural oils: release mechanism from gel emulsion, stability, and dermatological compatibility

Due to their broad spectrum of biological activities and attractive pharmacological properties, flavonoids are very promising molecules for application in skin care products. In this study, phloridzin and naringin medium- and long-chain fatty acid esters were enzymatically synthesized in reaction with natural oils (coconut and linseed oil) and in vitro transdermal delivery of synthesized esters through artificial Strat-M® membrane was investigated. Experimental results were succesfully fitted using Peppas and Sahlin model which includes the lag phase. Release kinetics of all examined flavonoid esters from gel emulsions through the membrane depended on both diffusion and polymer relaxation effect (0.5<n < 1). The estimated effective diffusion coefficients ranged from 0.168·10-8 to 6.149·10-8 cm2 s-1 for phloridzin esters and from 0.116·10-8 to 4.210·10-8 cm2 s-1 for naringin esters. The effective diffusion coefficients decreased with the increase in ester molecular weight indicating the size-dependent diffusion. All formulation showed good stability, excellent hydration effect, and excellent dermatological compatibility without irritating effect. It can be concluded that gel emulsions with a mixture of flavonoid esters enzymatically synthesized in reaction with vegetable oils can be effectively topically applied as a skin care products.

In vitro antimicrobial and antioxidant activities of bioactive compounds extracted from Streptomyces africanus strain E2 isolated from Moroccan soil

This study aimed to isolate Streptomyces sp. from Moroccan terrestrial ecosystems and identify bioactive compounds through GC–MS analysis. Antimicrobial activity was assessed against various pathogenic microorganisms including Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Candida albicans ATCC 60193, and multi-drug resistant strains comprising Listeria monocytogenes, Klebsiella pneumoniae 19K 929, Proteus sp. 19K1313, Klebsiella pneumoniae 20B1572, Proteus vulgaris 16C1737, and Klebsiella pneumoniae 20B1572. Based on the results of the gene sequencing of gene 16S rRNA and phylogenetic analysis, the E2 isolate belongs to the genus Streptomyces with the highest degree of resemblance (97.51%) to the Streptomyces africanus strain NBRC 101005 (NR_112600.1). The isolate exhibited broad-spectrum antibacterial activity, with maximum efficacy against Klebsiella pneumoniae 20B1572 indicated by an inhibition zone diameter of 22.5 ± 0.71mm and a minimum inhibitory concentration (MIC) of 0.0625 mg/mL. The in vitro antioxidant potential of E2 strain was determined through screening of its ethyl acetate extract against sets of antioxidant assays. The results were indicative of E2 strain displaying strong antioxidant activity against ABTS, DPPH free radicals, and FRAP. Furthermore, there was a high significant correlation (p < 0.0001) between the total phenolic and flavonoid content and antioxidant activities. The GC–MS analysis of the extract identified six volatile compounds, with Eugenol (96%) and Maltol (93%) being the most prominent. Additionally, the HPLC–UV/vis analysis revealed six phenolic compounds: gallic acid, chlorogenic acid, vanillic acid, trans-ferulic acid, ellagic acid, and cinnamic acid. Overall, the study highlights Streptomyces sp. strain E2 as a potential source of potent antimicrobial and antioxidant metabolites, offering promise in addressing antibiotic resistance and oxidative stress-related conditions.

A coronaviral pore-replicase complex links RNA synthesis and export from double-membrane vesicles.

Coronavirus-infected cells contain double-membrane vesicles (DMVs) that are key for viral RNA replication and transcription, perforated by hexameric pores connecting the vesicular lumen to the cytoplasm. How pores form and traverse two membranes, and how DMVs organize RNA synthesis, is unknown. Using structure prediction and functional assays, we show that the nonstructural viral membrane protein nsp4 is the key pore organizer, spanning the double membrane and forming most of the pore lining. Nsp4 interacts with nsp3 on the cytoplasmic side and with the viral replicase inside the DMV. Newly synthesized mRNAs exit the DMV into the cytoplasm, passing through a narrow ring of conserved nsp4 residues. Steric constraints imposed by the ring predict that modified nucleobases block mRNA transit, resulting in broad-spectrum anticoronaviral activity.

Whole Genome Sequencing and Comparative Genomic Analysis of Pseudomonas aeruginosa SF416, a Potential Broad-Spectrum Biocontrol Agent Against Xanthomonas oryzae pv. oryzae

Rice is one of the most important staple crops worldwide. However, the bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) poses a major threat to the production of rice. In this study, we isolated and identified the strain Pseudomonas aeruginosa SF416, which exhibited significant antagonistic activity against Xoo, from a soil sample collected in a winter wheat field in Shannanzhalang County, Tibet, China. The bacterial solution (BS) and cell-free supernatant (CFS) of SF416 had significant prevention effects for the bacterial blight of rice, with an efficacy of 45.1% and 34.18%, respectively, while they exhibited a slightly lower therapeutic efficiency of 31.64% and 25.09%. The genomic analysis showed that P. aeruginosa SF416 contains genes involved in cell motility, colonization, cold and hot shock proteins, antibiotic resistance, and plant growth promotion. SF416 also harbors two sets of phenazine-1-carboxylic acid (PCA) synthesis gene clusters, phz1 (phzA1-G1) and phz2 (phzA2-G2), and other phenozine product-synthesis--related genes phzS, phzM, and phzH, as well as genes in the SF416 genome that share high similarity with the ones in the genomes of P. aeruginosa M18, suggesting that the two sets of PCA synthesis gene clusters are responsible for the antagonistic effect of SF416 against Xoo. A comparative antiSMASH analysis revealed that P. aeruginosa SF416 contains 17 gene clusters related to secondary metabolite synthesis, 7 of which, encoding for pyochelin, azetidomonamide A/B, L-2-amino-4-methoxy-trans-3-butenoic acid, hydrogen cyanide, pyocyanine, pseudopaline, and bicyclomycin, are conserved in strains of P. aeruginosa. Moreover, SF416 can produce protease and siderophores and display a broad-spectrum antagonistic activity against various major plant pathogenic bacteria and fungi. The results suggest that P. aeruginosa SF416 could be a potential candidate agent for the bacterial blight of rice.

Role of Peptide Associations in Enhancing the Antimicrobial Activity of Adepantins: Comparative Molecular Dynamics Simulations and Design Assessments

Adepantins are peptides designed to optimize antimicrobial biological activity through the choice of specific amino acid residues, resulting in helical and amphipathic structures. This paper focuses on revealing the atomistic details of the mechanism of action of Adepantins and aligning design concepts with peptide behavior through simulation results. Notably, Adepantin-1a exhibits a broad spectrum of activity against both Gram-positive and Gram-negative bacteria, while Adepantin-1 has a narrow spectrum of activity against Gram-negative bacteria. The simulation results showed that one of the main differences is the extent of aggregation. Both peptides exhibit a strong tendency to cluster due to the amphipathicity embedded during design process. However, the more potent Adepantin-1a forms smaller aggregates than Adepantin-1, confirming the idea that the optimal aggregations, not the strongest aggregations, favor activity. Additionally, we show that incorporation of the cell penetration region affects the mechanisms of action of Adepantin-1a and promotes stronger binding to anionic and neutral membranes.

Whole Genome Sequencing and Biocontrol Potential of Streptomyces luteireticuli ASG80 Against Phytophthora Diseases

Phytophthora-induced crop diseases, commonly known as “plant plagues”, pose a significant threat to global food security. In this study, strain ASG80 was isolated from sisal roots and demonstrated a broad-spectrum antagonistic activity against several Phytophthora species and fungal pathogens. Strain ASG80 was identified as Streptomyces luteireticuli via phylogenetic analysis, digital DNA–DNA hybridization (dDDH), and average nucleotide identity (ANI). Whole-genome sequencing identified 40 biosynthetic gene clusters (BGCs) related to secondary metabolite production, including antimicrobial compounds. Strain ASG80 extract exhibited broad-spectrum inhibitory activity against Phytophthora nicotianae, P. vignae, P. cinnamomi, and P. sojae. Pot experiments showed that strain ASG80 extract significantly reduced sisal zebra disease incidence, with an efficacy comparable to the fungicide metalaxyl. These findings suggest that strain ASG80 is a promising biocontrol agent with substantial potential for managing Phytophthora-related diseases in agriculture.

Emergence of the mobile RND-type efflux pump gene cluster tmexCD1-toprJ1 in Klebsiella pneumoniae clinical isolates in Japan.

Tigecycline is an antimicrobial agent with a broad spectrum of activity against both Gram-positive and Gram-negative bacteria. However, mobile tigecycline resistance gene clusters, such as tnfxB-tmexCD-toprJ, have spread globally. The prevalence of tigecycline-resistant Enterobacterales in clinical settings in Japan is unknown. To investigate the tnfxB-tmexCD-toprJ gene cluster in the genome sequences of Enterobacterales clinical isolates in Japan. We investigated the tnfxB-tmexCD-toprJ cluster from the genome sequences of 5143 Enterobacterales isolates collected from 175 hospitals around Japan between 2019 and 2020 as part of a national genomic surveillance program for antimicrobial-resistant bacteria. The tnfxB1-tmexCD1-toprJ1 cluster was detected in two Klebsiella pneumoniae isolates in 2019. One isolate possessed a 299.4 kb IncFIB(K) plasmid, pJBBGAAF19431, and the other possessed a 224.9 kb IncHI1B/IncFIB(K) hybrid plasmid, pJBEAACG19501, co-carrying multiple antimicrobial resistance genes, including extended-spectrum β-lactamase genes, blaOXA-1 and blaCTX-M-27, respectively, along with tnfxB1-tmexCD1-toprJ1. The genetic context of the tnfxB1-tmexCD1-toprJ1-surrounding structure on pJBBGAAF19431 was similar to that of a K. pneumoniae plasmid pHNAH8I-1 from a chicken in China in 2017, and the cluster was embedded in an apparently intact mobile DNA element: strand-biased circularizing integrative element. The tnfxB1-tmexCD1-toprJ1 on pJBEAACG19501 was embedded in a Tn3 family transposon related to TnAs1. The plasmid pJBEAACG19501 was highly similar to that of K. pneumoniae, isolated from humans in China in 2021. tmexCD-toprJ was present in Japan as of 2019. Even in Japan, where the clinical use of tigecycline is significantly rare, tmexCD-toprJ-harbouring multidrug-resistant Enterobacterales is a public health threat and requires continuous monitoring.

Synthetic studies on the tetrasubstituted D-ring of cystobactamids lead to potent terephthalic acid antibiotics

Novel scaffolds for broad-spectrum antibiotics are rare and in strong demand because of the increase in antimicrobial resistance. The cystobactamids, discovered from myxobacterial sources, have a unique hexapeptidic scaffold with five arylamides and possess potent, resistance-breaking properties. This study investigates the role of the central D-ring pharmacophore in cystobactamids, a para-aminobenzoic acid (PABA) moiety that is additionally substituted by hydroxy and isopropoxy functions. We varied the two oxygenated substituents and replaced both amide connectors with bioisosteres. Synthetic routes were developed that included metal-mediated aromatic functionalization or heterocycle formations, leading to 19 novel analogues. The antibiotic efficacy of all analogues was determined against bacteria from the ESKAPE pathogen panel. While the replacement and the repositioning of hydroxy and isopropoxy substituents was not advantageous, exchanging PABA by terephthalic acid amides led to the highly potent analogue 42 with broad-spectrum activity, insensitivity towards AlbD-mediated degradation and promising pharmacokinetic properties in mice. The study highlights the steep structure-activity relationships in the tetrasubstituted D-ring and a surprisingly favorable reversion of the amide connecting C and D.

Thanatin and vinyl sulfide analogues as narrow spectrum antimicrobial peptides that synergise with polymyxin B

Thanatin is a β-hairpin antimicrobial peptide cyclised by a single disulfide bond that has shown potent broad-spectrum activity towards bacterial and fungal pathogens. Towards Gram-negative species, thanatin acts both by forming trans-membranal pores and inhibiting outer membrane biogenesis by binding to LptA and blocking lipopolysaccharide (LPS) transport. Inspired by previous modifications of thanatin, an analogue was prepared which demonstrated potent but selective activity towards E. coli. Furthermore, this compound was shown to act in synergy with the highly potent FDA-approved lipopeptide antibiotic polymyxin B, which engages LPS at the cytoplasmic membrane. Four analogues of thanatin in which the disulfide was substituted for vinyl sulfide bridge mimetics were prepared, all of which retained similar secondary structures. Two of these retained substantial potency and selectivity towards E. coli. Importantly, synergy with polymyxin B was also maintained for the lead analogue. The vinyl sulfide potentially offers a facile replacement strategy for labile disulfide bonds and the selective activity and drug synergy of the reported thanatin analogues is promising for the development of narrow spectrum antimicrobials with reduced likelihood of resistance emerging in clinical settings.

Design, Synthesis, and Antitumor Potential of New Thiazole--contained 5-Fluoro-2-Oxindole Derivatives as Sunitinib Analogues.

Indole is considered the most promising scaffold for anticancer drug design due to its high bioavailability, unique chemical properties, and broad spectrum of pharmacological action. Twelve novel thiazole-containing the 5-fluoro-1,3-dihydro-2H-indol-2-one derivatives as sunitinib analogs were designed and synthesized, and their anticancer activity was evaluated against the NCI-60 cancer cell lines. The thiazole-contained 5-fluoro-1,3-dihydro-2H-indol-2-one derivatives were synthesized using Knoevenagel condensation of 1,3-thiazole-5-carboxylic acid 1. Their anticancer activities were evaluated by NCI-60 one-dose screen assay. The molecular docking studies were performed using AutoDock tools and the AutoDock Vina programs. The ADMETlab 2.0 web server predicted the physicochemical properties of compounds. Among the synthesized new 5-fluoro-2-oxindole derivatives, compound 3g demonstrated high antitumor activity (GI>70%) against eight types of cancer: leukemia, breast cancer, ovarian cancer, lung cancer, melanoma, CNS cancer, renal cancer, and colon cancer. The most activity was observed against breast cancer (T-47D, GI=96.17%), lung cancer (HOP-92, GI=95.95%), ovarian cancer (NCI/ADR-RES, GI=95.13%), and CNS cancer (SNB-75, GI=89.91%). The molecular docking results of compound 3g demonstrated the possibility of inhibiting VEGF2 receptors as his potential anticancer mechanism. The physicochemical properties predicted for compounds 3f and 3g showed positive results. Compound 3g demonstrated high in vitro NCI-60 anticancer activity against nine cancer types and showed cell growth inhibition against leukemia, CNS, and breast cancer at 6 - 31% higher than Sunitinib, and may represent the basis for further modification of the thiazole-containing analogs of the anticancer drug Sunitinib.

Screening and computational characterization of novel antimicrobial cathelicidins from amphibian transcriptomic data

As cold-blooded organisms living in damp and dark environments, amphibians have evolved robust defense mechanisms to protect themselves from predators and infections. Among the wide repertoire of bioactive compounds they produce are antimicrobial peptides (AMPs), which are required as part of innate immunity. One important class of AMPs is cathelicidins, known for their broad-spectrum activity against pathogens and their immunoregulatory roles. However, despite their promising biomedical potential and the increasing availability of omics data, few cathelicidins have been studied in amphibians, mostly through conventional experimental techniques. Here, we present 210 novel cathelicidin sequences from amphibian transcriptomes, identified through a comprehensive computational pipeline, which employed HMMER and BLAST tools to screen cathelicidin domains. These sequences reveal a typical tripartite domain architecture that was confirmed by SignalP and InterProScan analysis. Phylogenetic inference with IQ-TREE classified the sequences into six categories based on evolutionary relationships. Compared to cathelicidins from other vertebrates, amphibian mature peptides exhibit longer average lengths (around 50 amino acids), fewer aromatic and hydrophobic residues, and reduced thermal stability. Furthermore, these amphibian cathelicidins were characterized for their physicochemical and biological properties, revealing significant antimicrobial potential with lower hemolytic capability, especially in anurans, which suggests a balance between their antimicrobial and hemolytic activities predicted through AMPlify, ampir, AmpGram, and HemoPI. Secondary structure estimations, including three-dimensional modeling using AlphaFold2, indicate that amphibian cathelicidins predominantly feature α-helices and coils. Some representative models also display a high α-helix composition with amphipathic topology, facilitating interactions with simulated bacterial membranes as assessed by the PPM approach. Thus, these findings highlight the functional role of cathelicidins in amphibian immunity and their promising biomedical applicability, emphasizing the importance of applying computational methods to expand the scope and reveal the diverse landscape of cathelicidins across vertebrates.

Baicalin nanofiber membranes: A comprehensive study on preparation, characterization, and antimicrobial pharmacological activities

Baicalin is a natural active ingredient known for its medicinal properties and a broad spectrum of pharmacological activities, including antimicrobial, antioxidant, antiviral, and anticancer effects. However, its application is hindered by its poor water-solubility. In this study, we aimed to enhance the water solubility of baicalin by embedding it within the hydrophobic cavity of hydroxypropyl-β-cyclodextrin through supramolecular assembly to form inclusion complexes. The inclusion complexes were subsequently processed into nanofiber membranes suitable for application on skin and wounds using coaxial electrostatic spinning. The inclusion complexes and nanofiber membranes were analyzed and characterized using high-performance liquid chromatography (HPLC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combined results from XRD, FT-IR, and TGA confirmed that baicalin successfully formed inclusion complexes with cyclodextrin, resulting in an increase in water solubility from 0.0170 mg/mL to 8.9600 mg/mL, representing a 527-fold enhancement. Additionally, the inclusion complexes demonstrated superior antimicrobial activity against E. coli, S. aureus and C. albicans, as well as higher free radical scavenging rates compared to native baicalin. After the inclusion complexes were transformed into nanofiber membranes via coaxial electrospinning, their properties remained unchanged, and they continued to exhibit excellent antimicrobial and antioxidant activities. In the in vitro release assay, nearly 90% of the drug (baicalin) was released from the nanofiber membranes over a period of time, indicating sustained release. Furthermore, the molecular docking mechanism of baicalin and cyclodextrin was elucidated through molecular docking simulations, establishing a theoretical foundation for the synthesis of inclusion complexes in the computational studies. This study reports the successful fabrication of water-soluble, antimicrobial nanofiber membranes containing bioavailable baicalin, which have potential clinical applications in the development of wound dressings and drug delivery systems utilizing plant-extracted bioactive compounds.

Design, Synthesis, and Biological Evaluation of Some Novel Retinoid Derivatives

Background: As cancer stands as a significant global health concern, many heterocyclic compounds that are more effective in cancer cells than healthy cells are being investigated for their selective anticancer potentials. One such compound is fenretinide, a synthetic derivative of retinoic acid that has a broad spectrum of cytotoxic activity against primary tumor cells, cell lines, and/or xenografts of various cancers. In this context, bexarotene and its derivatives, synthesized from hybridization of the fenretinide, are expected to possess a potential anticancer activity. Objective: The objective of the present study was to investigate the synthesis of novel amid-derived and bexarotene-based compounds, as well as to assess their cytotoxic effects in different cancer cell lines. Methods: This study involved the synthesis of twelve novel retinoid derivatives (6-17) in a six-step process. The cytotoxic activities of these compounds were assessed against various cancer cell lines, such as A549 (human lung carcinoma), HeLa (human cervical cancer), MCF7 (human breast adenocarcinoma), and WiDr (human colon adenocarcinoma). The chemical structures of these compounds were elucidated through their elemental analysis, mass spectrometry (ESI+, ESI-), as well as 1H-NMR and 13C-NMR spectroscopic data. Results: The obtained cell toxicity results indicated that compounds 6, 8, 11, 12, 13, 14, and 17 were found to exhibit the strongest cytotoxic activity in above mentioned cancer cell lines. The IC50 values for active compounds, 11 and 12, were determined as 2.38μM and 2.29μM, respectively. Remarkably, these compounds displayed higher cytotoxic activity in the WiDr cell line related to positive control, camptothecin (CPT). Moreover, compounds 14 and 17 demonstrated very similar level of cytotoxic activity to CPT, indicating their potential for antitumoral applications upon further studies. Conclusion: While compounds 11, 12, 14, and 17 indicated a very comparable anticancer activity to CPT, compounds 6, 8, 11 and 12 showed more selective anticancer effect against cancer cells than noncancerous cells. In accordance with the findings of the present study, they can be evaluated as primary candidates for further studies, specifically as RXRα-targeted anticancer agents.

Functional interplay between short antimicrobial peptides and model lipid membranes

Antimicrobial peptides (AMPs) are considered an attractive generation of novel antibiotics due to their advantageous properties such as a broad spectrum of antimicrobial activity against pathogens, low cytotoxicity, and drug resistance. Although they have common structural features and it has been widely demonstrated that bacterial membranes represent the main target of the peptide activity, the exact mechanism underlying the membrane perturbation by AMPs is not fully understood. Nevertheless, all the proposed modes of action implicate the preliminary interaction of AMPs with the negatively charged lipids in bacterial membranes. Recently, the structural and functional characterization of two AMPs, RiLK1 and RiLK3, was reported. Specifically, both peptides were revealed to be multitalented compounds capable of binding Gram-positive and Gram-negative liposome models with high affinity, but their mechanism of action remains elusive. In this paper, the effects of RiLK1 and RiLK3 on vesicles mimicking prokaryotic and eukaryotic cell membranes were further examined by using different approaches. Fluorescence and quenching assays either by acrylamide or lipophilic probes suggested that the peptides were mainly located at the interface of the negatively charged membranes that mimicked those of Salmonella Typhimurium and Staphylococcus aureus, possibly oriented in a parallel manner. Furthermore, RiLK1 and RiLK3 caused a significant leakage of carboxyfluorescein from bacterial liposomes, demonstrating that they can permeabilize the target membranes at high doses. Conversely, both peptides appear to behave like cell penetrating peptides (CPPs) at concentrations near their MIC values evaluated against the bacterial targets. Moreover, Dynamic Light Scattering provided further insights on the mechanisms of antimicrobial peptide against the bacterial liposomes. Conclusively, in vitro experiments indicated that RiLK1 and RiLK3 displayed potent bacteriostatic efficacy at low micromolar concentrations against an antibiotic-resistant ESKAPE pathogen, making them a valuable tool in preventing and treating infections caused by such bacteria.

Development of α-Helical Antimicrobial Peptides with Imperfect Amphipathicity for Superior Activity and Selectivity.

The advancement of antimicrobial peptides (AMPs) as therapeutic agents is hindered by their poor selectivity. Recent evidence indicates that controlled disruption of the amphipathicity of α-helical AMPs may increase the selectivity. This study investigated the role of imperfect amphipathicity in optimizing AMPs with varied sequences to enhance their activity and selectivity. Among these, the lead peptide RI-18, characterized by an imperfectly amphipathic α-helical structure, demonstrated potent and broad-spectrum antibacterial activity without inducing hemolytic or cytotoxic effects. RI-18 effectively eliminated planktonic and biofilm-associated bacteria as well as persister cells and exhibited high bacterial plasma membrane affinity, inducing rapid membrane permeabilization and rupture. Notably, RI-18 significantly reduced bacterial loads without promoting bacterial resistance, highlighting its therapeutic potential. Overall, this study identified RI-18 as a promising antimicrobial candidate. The rational strategy of tuning imperfect amphipathicity to enhance the AMP activity and selectivity may facilitate the design and development of AMPs.

Thymol as adjuvant in oncology: molecular mechanisms, therapeutic potentials, and prospects for integration in cancer management.

Cancer remains a global health challenge, prompting a search for effective treatments with fewer side effects. Thymol, a natural monoterpenoid phenol derived primarily from thyme (Thymus vulgaris) and other plants in the Lamiaceae family, is known for its diverse biological activities. It emerges as a promising candidate in cancer prevention and therapy. This study aims to consolidate current research on thymol's anticancer effects, elucidating its mechanisms and potential to enhance standard chemotherapy, and to identify gaps for future research. A comprehensive review was conducted using databases like PubMed/MedLine, Google Scholar, and ScienceDirect, focusing on studies from the last 6years. All cancer types were included, assessing thymol's impact in both cell-based (in vitro) and animal (in vivo) studies. Thymol has been shown to induce programmed cell death (apoptosis), halt the cell division cycle (cell cycle arrest), and inhibit cancer spread (metastasis) through modulation of critical signaling pathways, including phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), extracellular signal-regulated kinase (ERK), mechanistic target of rapamycin (mTOR), and Wnt/β-catenin. It also enhances the efficacy of 5-fluorouracil (5-FU) in colorectal cancer treatments. Thymol's broad-spectrum anticancer activities and non-toxic profile to normal cells underscore its potential as an adjunct in cancer therapy. Further clinical trials are essential to fully understand its therapeutic benefits and integration into existing treatment protocols.