Background/Objectives: Antibiotic resistance in bacteria poses a major health problem worldwide. Therefore, to counteract this life-threatening problem, we sought to investigate in the present study the possible potentiation of the efficacy of amoxicillin (AMX) and clavulanic acid (CA) by 1,8-cineole (CN), a candidate resistance-modulating agent. The approach seeks to investigate, in vitro and in silico, the interactions among these three molecules. Methods: The antibacterial activity was determined against resistant Escherichia coli (E. coli) using microdilution methods, synergy tests, and time-kill assays for AMX, CA, and CN, used either separately or in combinations: AMX–CA, AMX–CN, CA–CN, and AMX–CA–CN. Furthermore, an in silico drug design methodology was employed, utilizing an integrated workflow that combines Density Functional Theory (DFT) for ligand optimization with molecular docking simulations to evaluate binding energies and interactions between the penicillin-binding protein (PBP) and ligands. Results: In vitro synergy experiments and time-kill assays revealed substantial antibacterial efficacy of the AMX–CA–CN combination. In silico analyses, performed under the simplifying assumption of a pre-assembled multi-ligand entity, were consistent with these findings: within our docking model, the AMX–CA–CN combination exhibited the most favorable computed binding affinity to a representative penicillin-binding protein (PBP3, PDB 7ONW). Conclusions: 1,8-cineole can potentiate the antibacterial effects of AMX–CA, indicating that the AMX–CA–CN combination warrants further evaluation as a candidate adjunctive strategy against ESBL-producing E. coli.

The purpose of this study was to evaluate the antifungal effects of thymol on fungi planktonic and biofilm cells. Firstly, the antifungal activity of a thymol-based product on reducing fungi load in poultry drinking water samples was assessed in vitro using the plate count method. Samples were treated by increasing concentrations of thymol (1, 2 and 4 g.l^-1 of product). Reduction is about one log unit for 1 g.l^-1, about two log units for 2 g.l¹, and a total desperation for 4 g.l^-1. Secondly, the antifungal activity was tested on biofilms formed on coiled pipes using an experimental arrangement simulating animals watering conditions in poultry farming. Two concentrations (1 and 2 g.l^-1) were used in two ways, preventive and curative treatment. The first one consisted in preventing fungal development on pipes and the biofilm formation. The second consisted in treating biofilms that have already settled on pipes. The plat count method was used to check the antifungal activity of thymol. Data of this experiment data have shown that thymol may prevent Candida albicans and Aspergillus niger proliferation in the experimental arrangement. After just a week, a significant reduction (P<0,05) was shown with the concentration 1 g.l^-1. The reduction was much important when the product was used at a concentration of 2 g.l^-1 (about tree log units). For curative treatment, results showed a significant reduction (P<0,05) of C. albicans load after only 24 hours with 1 g.l^-1 (about one log unit). With this same concentration, reduction is more important over time for both spices (about four log units after a week). A significant reduction (more than two log units) was showed in just 24 hours of treatment with the concentration of 2 g.l^-1. This work offers an alternative solution to chemical biocides, which can treat water and disinfect distribution system in poultry farming.

Using essential oils (EOs) and their primary compounds to protect stored grains from insect infestations offers a promising alternative to synthetic insecticides. This study tested thymol, a major constituent of thymus EO (Thymus vulgaris), for its insecticidal effects on the maize weevil, Sitophilus zeamais (S. zeamais). The repellent activity was evaluated using a preferred zone method, where insects were given the choice between treated and untreated areas. This method demonstrated significant repellent effects across all tested concentrations, with repellency rates exceeding 80% at a concentration of 300 µL/mL. In fumigant activity tests, the concentration of 300 μL/mL achieved highly significant results, with a mortality rate of 98% by the fourth day of treatment. Additionally, topical exposure of insects to thymol showed significant insecticidal activity, with mortality rates of 81% and 100% at doses 0.06 and 0.12 μL per insect, respectively. Insects exposed to grains treated with concentrations of 1.2, 1.8, and 2.4 µL/mL exhibited 100% mortality within 7 days. Significant differences were also found between treated and untreated grains for weight loss, hole percentage, and the inhibition of progeny insects, irrespective of the concentration. The molecular docking simulations of thymol against the Acetylcholinesterase protein (PDB ID: 7E3H), showed that thymol interacts strongly with this protein target (binding energy of -7.291 kcal/mol), suggesting potential neurotoxic effects on S. zeamais. These findings highlight thymol's potential as a natural and effective alternative to synthetic insecticides for the protection of stored grains against weevil infestations, offering a promising solution for safer post-harvest management. Keywords: Insecticidal activity, fumigation, repellency, molecular docking, sitophilus zeamais, thymol.

Antibiotic resistance is a growing global health threat, driving increasing interest in combining conventional antibiotics with natural compounds to restore or enhance antibacterial efficacy while reducing antibiotic resistance. Among such strategies, the combination of amoxicillin-clavulanic acid with the essential oil component 1,8-cineole has emerged as a particularly promising approach. The aim of this study is to evaluate the molecular interactions between amoxicillin (AMOX), clavulanic acid (CA), and the essential oil component 1,8-cineole (CN). UV–Vis spectroscopy and density functional theory (DFT) calculations were used to investigate the interactions of AMOX, CA, and CN in binary and ternary systems. The UV–Vis spectra showed consistent negative deviations from spectral additivity, particularly for the CA–CN system, indicating changes in the electronic environment of the molecules upon association. DFT calculations at the B3LYP/6-31G(d) level were then performed to characterize the corresponding molecular complexes and their intermolecular interactions. The AMOX–CN, CA–CN, AMOX–CA, and AMOX–CA–CN complexes were found to be stabilized by well-defined intermolecular hydrogen-bond interactions. Molecular electrostatic potential (MEP) maps and reduced density gradient (RDG) analysis further supported the presence and noncovalent character of these interactions. Overall, the experimental and computational results support the formation of molecular complexes involving AMOX, CA, and CN and provide a molecular-level explanation for the interactions observed in these systems. These findings may help clarify how CN interacts with the components of AMOX–CA and contribute to the understanding of its previously reported antibacterial potentiating effects.