Search Results (160)

Schiff bases are bioactive compounds that have been synthesized by many researchers in recent years. They may also exhibit strong antimicrobial activities against various pathogenic microorganisms in both medicine and veterinary applications. The synthesis of new Schiff base-derived compounds remains of interest due to the increasing problem of antibiotic-resistance in clinical practice. Seven new Schiff base derivatives were synthesized, and their chemical structures were characterized using FT-IR, ¹H/¹³C NMR, and LCMS-MS analyses. The antimicrobial activities of thesyntesized compounds against various pathogenic bacteria, yeasts, and fungi were evaluated using the disk-diffusion method, and their MIC values were also determined. In addition, one representative microorganisms from each class were selected for molecular docking studies. IFD analyses were performed for the 4f and 4g ligands using the dihydrofolate reductase enzyme. Spectroscopic analyses confirmed the structures of the synthesized compounds, revealing the presence of characteristic imine functionalities and validating the integrity of the molecular frameworks. Antimicrobial assays demonstrated that several derivatives exhibited measurable activity, with compounds 4f and 4g showing the most potent effects, displaying MIC values of 32 µg/mL against B. cereus and E. faecalis, respectively. Molecular docking studies further indicated that both 4f and 4g bind efficiently to the DHFR active site. These findings indicate that among the synthesized Schiff base derivatives, compounds 4f and 4g exhibit particularly promising antimicrobial activity, warranting further pharmacological evaluation and medicinal chemistry optimization. Full article

Background/Objectives: Malaria is a tropical disease mainly caused by Plasmodium falciparum and represents a global public health problem, with over 200 million cases and 500 thousand deaths reported worldwide. Considering its treatment limitations, it is essential to develop new compounds against malaria. In this context, acridine derivatives are privileged structures. Methods: Thus, new spiroacridines containing N-acylhydrazone (AMTAC) and N-phenylacetamide (ACMD) were synthesized and evaluated in malaria and cytotoxicity assays, as well as in silico studies. Results: As a result, five spiroacridines showed inhibitory activity over 70% against the P. falciparum 3D7-GFP strain at 10 μM, along with an IC₅₀ range of 2–4 μM. After a brief Structure–Activity Relationship (SAR) analysis, it was observed that the spiroacridine structure must be associated with the hydrazone moiety to successfully inhibit parasite growth. In addition, these molecules presented promising resistance profile, with selectivity for the parasite. After computational studies, spiroacridines showed better affinity with dihydrofolate reductase (DHFR), overcoming the quadruple mutant resistance to pyrimethamine, with more stability in complex with the enzyme. Conclusions: Therefore, the potential of spiroacridines against malaria, with moderate resistance and selectivity profile, as well as DHFR inhibition greater than pyrimethamine, was confirmed. Full article

Human dihydrofolate reductase (hDHFR) is a crucial cellular enzyme in folate metabolic pathway, where it catalyzes the reduction of dihydrofolate into tetrahydrofolate (THF) and an important cofactor involved in DNA, RNA, protein biosynthesis and cell proliferation. Due to its importance, hDHFR has become a promising target for therapeutic development, particularly in treating cancer, bacterial infections, and autoimmune diseases. Its inhibition has found clinical value in antitumor, antimicrobial and antiprotozoal treatment; however, the emergence of resistance to existing hDHFR inhibitors necessitates the development of new and more potent compounds. In the current study, we propose a cheminformatics-based approach using machine learning to develop predictive models of hDHFR bioactivity. We used three types of molecular descriptors in the form of fingerprints, i.e., PubChem, Substructure, and MACCS, to capture structural properties associated with hDHFR inhibition. Predictive models were built using a random forest algorithm optimized through hyperparameter tuning. Feature selection was performed using Recursive Feature Elimination (RFE), and dataset dimensionality was reduced by removing outliers through Principal Component Analysis (PCA) to optimize model performance and reducing overfitting and weak predictivity. The resulting models are validated through external test sets, domain applicability analysis, and interpretation of influential molecular features via random forest feature importance selection plots and correlation matrix analysis. All three models exhibited strong predictive capabilities, with R-squared (R²) values ranging from 0.9849 to 0.9934 for the training set and 0.9381 to 0.9591 for the test set. These final predictive models were further incorporated into an accessible web application, enabling users to estimate the bioactivity of new compounds targeting hDHFR. Full article

Background/Objectives: In the Brazilian Amazon, which accounts for over 99% of national malaria cases, 34,260 cases were reported as of August 2025, predominantly caused by Plasmodium vivax, responsible for 86.69% of the infections. The increasing resistance of the parasite to conventional therapies highlights the urgent need for novel control strategies, with essential oils and plant-derived substances emerging as promising alternatives. Methods: In this context, we evaluated the anti-Plasmodium potential of Piper alatipetiolatum essential oil and its major constituent 6-ishwarone against P. vivax, including cytotoxicity in Vero and PBMCs, molecular docking on dihydrofolate reductase (DHFR) and lactate dehydrogenase (LDH), and in silico pharmacokinetic profiling. Results: Both the oil and 6-ishwarone inhibited P. vivax dose-dependently (2.1 ± 1 to 100%), with IC₅₀ values of 9.25 µg/mL and 3.93 µg/mL, respectively. Importantly, no cytotoxic effects were observed at 24 h, with cell viability ranging from 94.7% to 98.3%, highlighting the selectivity of these compounds towards the parasite over mammalian cells. Docking studies indicated selective binding of 6-ishwarone to DHFR (−7.7 kcal/mol; Ki = 2.27 µM) with key interactions (Trp816, Lys820, Tyr819, Asn823, Thr865), whereas binding to LDH was weaker (−6.2 kcal/mol; Ki = 28.10 µM), suggesting DHFR as the primary molecular target. In silico ADMET predictions and experimental data indicated favorable drug-like properties: TPSA = 20.23 Ų, moderate lipophilicity (LogP = 3.37), soluble (ESOL Log S = −3.58; Ali Log S = −3.89; Silicos-IT Log S = −2.84), high gastrointestinal absorption, BBB permeability (0.985), not a P-glycoprotein substrate (0.11), and low likelihood of CYP inhibition. Toxicity predictions showed non-mutagenic and non-hepatotoxic effects, low cardiotoxicity (hERG inhibition risk 0.08–0.32), low reproductive toxicity (0.03), moderate neurotoxicity (0.28), low acute toxicity (oral LD₅₀ = 2.061 mol/kg), and low chronic toxicity (LOAEL = 1.995 log mg/kg/day). Conclusions: Together, these findings demonstrate that essential oil and 6-ishwarone of P. alatipetiolatum are selective, bioavailable, and promising natural leads for antimalarial drug development. Full article

Parasitic diseases are some of the most lethal and pervasive infections globally, causing millions of cases of morbidity and mortality annually. Plasmodium falciparum is the predominant vector-borne pathogen, resulting in 0.5 million fatalities annually. Malaria, caused by Plasmodium falciparum, continues to be a significant worldwide health issue, requiring the development of novel treatment medicines to address increasing medication resistance. This study undertakes a focused in silico screening of phytochemicals derived from Centella asiatica against dihydrofolate reductase-thymidylate synthase (PfDHFR-TS), represented by PDB ID: 3BWK. This work investigated molecular modelling to clarify the probable mechanism of its anti-malarial activity through the suppression of falciparum proteins. Campesterol exhibits a maximal binding affinity (docking score: −8.6 Kcal/mol) for FP-2 from Plasmodium falciparum, as determined by our molecular docking investigation of 15 bioactive compounds from Centella asiatica. However, Ursolic acid and rutin also showed potential activity with significant docking scores (−8.5 and 8.4 Kcal/mol). Campesterol, recognized as a possible inhibitor of falciparum, offers a viable pathway for the treatment of malaria, necessitating additional investigation into its therapeutic use. This research provides significant insights into the molecular interactions between phytochemicals, facilitating innovative and successful strategies for malaria treatment. Our research indicates that polyphenols derived from Centella asiatica exhibit significant pharmacological potential against several biological targets. Full article

Background/Objectives: Leishmaniasis is an infectious disease caused by digenetic protozoa of the genus Leishmania, transmitted by infected female sandflies of the Phlebotominae subfamily. Current treatments are limited, relying on drugs that were not specifically developed for this disease and are often associated with high toxicity and elevated costs. Among alternative therapeutic strategies, antifolate compounds have been investigated due to their ability to inhibit dihydrofolate reductase (DHFR), an enzyme essential for folate metabolism in the parasite. However, the parasite circumvents DHFR inhibition through the activity of pteridine reductase-1 (PTR-1), which maintains folate reduction and ensures parasite survival. In this context, this study aimed to identify potential PTR-1 inhibitors in Leishmania major through in silico approaches. Methods: The methodology included virtual screening of molecular databases, Tanimoto similarity analysis, pharmacokinetic and toxicological predictions, and biological activity evaluation in silico. The most promising compounds were further analyzed via molecular docking. Results: The virtual screening resulted in 474 molecules, of which 4 structures (M601, M692, M700, and M703) showed high potential as PTR-1 inhibitors in Leishmania major throughout all stages of the methodology employed, especially in the results of molecular docking where they exhibited strong binding affinities and significant interactions with key residues of the target enzymes. Conclusions: This work provides a solid foundation for advancing these molecules into experimental validation, contributing to the development of safer and more effective therapeutic alternatives for the treatment of leishmaniasis. Full article

The worldwide increase in antifungal resistance, particularly in Candida sp., requires the exploration of novel therapeutic agents. Natural compounds have been a rich source of antimicrobial molecules, where peptides constitute the class of the most bioactive components. Therefore, this study looks into the target-specific binding efficacy of insect-derived antifungal peptides (n = 37) as possible alternatives to traditional antifungal treatments. Using computational methods, namely the HPEPDOCK and HDOCK platforms, molecular docking was performed to evaluate the interactions between selected key fungal targets, lanosterol 14-demethylase, or LDM (PDB ID: 5V5Z), secreted aspartic proteinase-5, or Sap-5 (PDB ID: 2QZX), N-myristoyl transferase, or NMT (PDB ID: 1NMT), and dihydrofolate reductase, or DHFR, of C. albicans. The three-dimensional peptide structure was modelled through the PEP-FOLD 3.5 tool. Further, we predicted the physicochemical properties of these peptides through the ProtParam and PEPTIDE 2.0 tools to assess their drug-likeness and potential for therapeutic applications. In silico results show that Blap-6 from Blaps rhynchopeter and Gomesin from Acanthoscurria gomesiana have the most antifungal potential against all four targeted proteins in Candida sp. Additionally, a molecular dynamics simulation study of LDM-Blap-6 was carried out at 100 nanoseconds. The overall predictions showed that both have strong binding abilities and are good candidates for drug development. In in vitro studies, Gomesin achieved complete biofilm eradication in three out of four Candida species, while Blap-6 showed moderate but consistent reduction across all species. C. tropicalis demonstrated relative resistance to complete eradication by both peptides. The present study provides evidence to support the antifungal activity of certain insect peptides, with potential to be used as alternative drugs or as a template for a new synthetic or modified peptide in pursuit of effective therapies against Candida spp. Full article

This study describes the synthesis of a series of dideaza analogs of methotrexate and their preliminary pharmacological and metabolic evaluation. The 5,8-dideazamethotrexate was efficiently obtained in five steps using a new synthetic route. Oxygenated and thiolated analogs of dideazamethotrexate were prepared following the devised pathway. Their cytotoxicity was studied in the A549 lung cancer cell line, as well as their DHFR dihydrofolate reductase inhibition activity and in vitro metabolism. The two new analogs showed strong activity on cancer cells and the enzymatic target. These compounds were not metabolized, a clear advantage over methotrexate, which is rapidly converted to the toxic metabolite 7-hydroxymethotrexate. Full article

Candida auris is an emerging multidrug-resistant fungal pathogen with a high affinity for skin colonization and significant potential for nosocomial transmission. This study aimed to develop and evaluate chitosan-based hydrogels loaded with nystatin and propolis as a topical antifungal strategy for skin decolonization of C. auris. The formulations were selected based on our previous results and optimized for cutaneous application. The internal structure of the hydrogels was investigated by polarized light microscopy, confirming the amorphous nature of propolis and the partial dispersion of nystatin. The antifungal activity was assessed against ten fluconazole-resistant C. auris strains. The CS-NYS-PRO1 formulation demonstrated the highest antifungal performance in the agar test, also reducing viable cell counts to undetectable levels within 6 h. Time–kill assays and SEM imaging confirmed the rapid fungicidal effect and revealed severe membrane disruption and cytoplasmic leakage. Molecular docking analyses indicated the strong binding of nystatin to both sterol 14α-demethylase (CYP51) and dihydrofolate reductase (DHFR) from C. auris, suggesting complementary membrane and intracellular mechanisms of action. These findings support the use of such hydrogels as a local, non-invasive, and biocompatible strategy for managing C. auris colonization, with promising implications for clinical use in infection control and the prevention of skin-mediated transmission in healthcare settings. Full article

The objectives of this study were to design, synthesize, and evaluate the antibacterial activity of a series of novel aminoguanidine-tetralone derivatives. Thirty-four new compounds were effectively synthesized through nucleophilic substitution reaction and guanidinylation reaction. Chemical structures of all the desired compounds were identified by NMR and HR-MS spectroscopy. Most of the synthesized compounds showed significant antibacterial activity against ESKAPE pathogens and clinically resistant Staphylococcus aureus (S. aureus) isolates. S. aureus is an important pathogen that has the capacity to cause a variety of diseases, including skin infections, pneumonia, and sepsis. The most active compound, 2D, showed rapid bactericidal activity against S. aureus ATCC 29213 and MRSA-2 with MIC/MBC values of 0.5/4 µg/mL and 1/4 µg/mL, respectively. The hemolytic activity and cytotoxicity of 2D was low, with HC₅₀ and IC_{50(HEK 293-T)} values of 50.65 µg/mL and 13.09 µg/mL, respectively. Compound 2D induced the depolarization of the bacterial membrane and disrupted bacterial membrane integrity, ultimately leading to death. Molecular docking revealed that dihydrofolate reductase (DHFR) may be a potential target for 2D. In the mouse skin abscess model caused by MRSA-2, 2D reduced the abscess volume, decreased bacterial load, and alleviated tissue pathological damage at doses of 5 and 10 mg/kg. Therefore, compound 2D may be a promising drug candidate for antibacterial purposes against S. aureus. Full article

Aquaculture is one of the fastest-growing sectors in food production. The widespread use of antibiotics in fish farming has been identified as a driver for the development of antibiotic resistance. One of the promising approaches to solving this problem is the use of probiotics. There are many promising aquaculture probiotics in the Bacillus genus, which produces non-ribosomal peptides (NRPs). NRPs are known as antimicrobial agents, although evidence is gradually accumulating that they may have other effects, especially at lower (subinhibitory) concentrations. The mechanisms of action of many NRPs remain unexplored, and molecular docking and molecular dynamics studies are invaluable tools for studying such mechanisms. The purpose of this study was to investigate the in silico inhibition of crucial bacterial targets by NRPs. Molecular docking analyses were conducted to assess the binding affinities of the NRPs of Bacillus for protein targets. Among the complexes evaluated, bacillibactin with glutamine synthetase, dihydrofolate reductase, and proaerolysin exhibited the lowest docking scores. Consequently, these complexes were selected for further investigation through molecular dynamics simulations. As a result, three additional potential mechanisms of action for bacillibactin were identified through in silico analyses, including the inhibition of glutamine synthetase, dihydrofolate reductase, and proaerolysin, which are critical bacterial enzymes and considered as the potential antibacterial targets. These findings were further supported by in vitro antagonism assays using bacillibactin-producing Bacillus velezensis strains MT55 and MT155, which demonstrated strong inhibitory activity against Pseudomonas aeruginosa and Aeromonas veronii. Full article

Cytokinins, plant hormones derived from adenine, are best known for regulating growth and stress responses in plants. Recent findings suggest they may also influence microbial viability, yet their direct antimicrobial potential remains underexplored. This study evaluates the antimicrobial activities of four natural cytokinins (iPA, B, K, and p-T) and their N⁹-ribosides (iPAR, BR, KR, and p-TR) against selected human pathogens. Using the broth microdilution method, we assessed their effects on Gram-positive and Gram-negative bacteria, as well as fungal strains. While Gram-negative species showed no susceptibility, all tested compounds exhibited bacteriostatic activity against Bacillus subtilis and Enterococcus faecalis. Most notably, kinetin (K) and kinetin riboside (KR) displayed strong antifungal activity against Candida albicans, with MIC values comparable to the reference drug nystatin. Molecular docking studies supported these findings by showing that K and KR form favorable interactions with two validated antifungal targets in Candida albicans: secreted aspartic proteinase 3 (SAP3) and dihydrofolate reductase (DHFR). This is, to our knowledge, the first report linking natural cytokinins to direct antifungal action against C. albicans supported by in silico evidence. These findings highlight the potential of K and KR as promising leads for the development of cytokinin-based antifungal agents. Full article

Toxoplasmosis is a significant parasitic zoonosis caused by Toxoplasma gondii. Among livestock animals, small ruminants, especially sheep and goats, are the most infected. This infection is a leading cause of abortion, resulting in considerable economic losses for goat breeders. The present study aimed to assess the prevalence of T. gondii infection in goats in northern Thailand, with an emphasis on its potential zoonotic transmission to humans. Polymerase chain reaction (PCR) targeting the T. gondii dihydrofolate reductase-thymidylate synthase (Tgdhfr-ts) gene was employed for molecular detection. This represents the first report of T. gondii molecular detection in blood samples from small ruminants in Thailand by PCR. A total of 176 meat goat blood samples were analyzed, yielding an 8.52% (15/176) positivity rate for T. gondii DNA. The selected DNA sequences from the positive T. gondii DNA displayed a high degree of nucleotide sequence homology with the reference Tgdhfr-ts sequence. Phylogenetic analysis revealed a single clade alongside other T. gondii strains, showing no differentiation based on genotype. This study contributes to the understanding of T. gondii epidemiology and provides a foundation for future strategies to control and manage T. gondii transmission in livestock populations. Full article

This study investigated the phytochemical composition and biological activities of Myrtus communis essential oil (EO) from Algeria, focusing on its antimicrobial, antifungal, and insecticidal properties using in vitro and in silico approaches. Gas chromatography–mass spectrometry (GC-MS) analysis identified myrtenyl acetate (57.58%), 1,8-cineole (17.82%), and α-terpineol (6.82%) as the major constituents. M. communis EO exhibited significant antibacterial activity, particularly against Staphylococcus aureus (13.00 ± 0.70 mm) and Salmonella typhimurium (13.00 ± 1.50 mm), with moderate inhibition of Bacillus subtilis (10 ± 1.00 mm) and Escherichia coli (9.00 ± 0.70 mm), while Pseudomonas aeruginosa showed resistance. The antifungal activity was notable against Fusarium oxysporum (16.50 ± 0.50 mm), Aspergillus fumigatus (11.00 ± 1.00 mm), and Penicillium sp. (9.00 ± 0.60 mm) but ineffective against Aspergillus niger. Insecticidal activity against Tribolium castaneum was evaluated using contact toxicity, fumigation toxicity, and repellent activity assays. The EO demonstrated potent insecticidal effects, with an LC₅₀ value of 0.029 µL/insect for contact toxicity and 162.85 µL/L air for fumigation after 96 h. Additionally, the EO exhibited strong repellent activity, achieving 99.44% repellency at a concentration of 0.23 mg/cm² after 24 h. Density functional theory (DFT) calculations provided insights into the molecular geometry and electronic properties of the key bioactive compounds. Molecular docking studies evaluated their binding affinities to bacterial enzymes (DNA gyrase, dihydrofolate reductase6, and Gyrase B) and insecticidal targets (acetylcholinesterase), revealing strong interactions, particularly for geranyl acetate and methyleugenol. These findings highlight M. communis EO as a promising natural antimicrobial and insecticidal agent, with potential applications in plant protection and biopesticide development. Full article

The protein sequence space is vast. This fact, together with the prevalence of epistasis, hampers the engineering of novel enzymes through library screening and is a major obstacle to any attempt to predict natural protein evolution. Recently, specialized methodologies have been used to determine fitness data on ~260,000 sequences for the gene of the enzyme dihydrofolate reductase and antibody affinity data for all combinations of the mutations present in the receptor-binding domain (RBD) of the Omicron strain of SARS-CoV-2 (~30,000 variants). We show that upon iterative training on a total of just a few hundred variants, various state-of-the-art AI tools (multi-layer perceptron, random forest, and XGBoost algorithms) find very high fitness variants of the enzyme and predict the antibody evasion patterns of the RBD. This work provides a basis for efficient, widely applicable, low-throughput experimental approaches to assess viral protein evolution and to engineer enzymes for biotechnological applications. Full article