Phytochemical Characterization by Maldi‐tof, Antioxidant and Antimicrobial Activities, and Action Mechanism of Tunisian <i>Thymus Numidicus</i> Extracts

Abstract

Abstract The characterization of the antimicrobial activity and the chemical composition of two extracts from Tunisian Thymus numidicus was studied in this investigation. MALDI‐TOF analysis revealed that the ethanolic extract contained a greater variety of chemical compounds than the methanolic extract. The results showed that the ethanolic extract had the highest levels of polyphenols (106.23 mg GAE/g DW), flavonoids (60.08 mg CE/g DW), flavanols (3.29 mg QE/g DW), and proanthocyanidins (20.78 mg CE/g DW). Regarding antioxidant capacity, the DPPH assay demonstrated that the ethanolic extract exhibited higher antioxidant activity than the methanolic extract. The antimicrobial effects of both extracts against bacterial species were assessed. The disc‐diffusion assay revealed variable inhibition zones, depending on the extract and bacterial strains. Both extracts exhibited strong antimicrobial activity against E.coli and S.aureus. In terms of mode of action, treatment with both extracts reduced the viability of E.coli and S.aureus strains. Additionally, the release of 260‐nm‐absorbing materials was observed following treatment with the extracts, indicating membrane damage. The extracts also significantly reduced the salt tolerance of bacterial strains. These findings suggest that the ethanolic extract inhibits or prevents the growth of these bacterial strains and may serve as a promising natural alternative to chemical antimicrobial agents.