In Vitro Antibacterial Activity and Chemical Characterization of a Laboratory-Prepared Thymus vulgaris L. Absolute against Clinical Bacterial Isolates Including Multidrug-Resistant Strains

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Background: Healthcare-associated infections are a major challenge, especially with the rise of antimicrobial-resistant and multidrug-resistant (MDR) pathogens. Plant-derived preparations, particularly absolutes obtained via solvent extraction, offer a promising alternative to conventional antibiotics and differ chemically from essential oils.Objective: This study aimed to prepare an absolute from Thymus vulgaris L. using low-temperature solvent extraction, characterize its chemical composition via GC-MS, and evaluate its antibacterial activity against clinical bacterial isolates, including MDR strains, by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Materials and Methods: Aerial parts of T. vulgaris were collected from Al-Jabal Al-Akhdar, Libya. The dried plant material was extracted with n-hexane at 35°C, followed by ethanol treatment to remove waxes. Antibacterial activity was evaluated using the disc diffusion method against 202 selected isolates. MIC and MBC were determined by broth microdilution, and the chemical composition was analyzed by GC-MS. Results: The absolute yield was 1.92 ± 0.12% (w/w), compared to 0.85 ± 0.08% for the steam-distilled oil. GC-MS identified 35 compounds, with thymol (42.5 ± 1.8%) and carvacrol (28.3 ± 1.5%) as the major constituents. The absolute exhibited concentration-dependent activity, with inhibition zones ranging from 6.2 to 34.1 mm. MIC values ranged from 1.25 to 10 µL/mL, while MBC values ranged from 2.5 to 20 µL/mL, with an MBC/MIC ratio ≤4. Conclusion: The T. vulgaris absolute demonstrated significant in-vitro antibacterial activity against clinical isolates, including MRSA and ESBL-producing strains. However, further studies on cytotoxicity, stability, and in-vivo efficacy are required before any therapeutic application can be considered.

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