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The objective of the present study is to the total phenolic compound determination, as well as the in vitro evaluation of methanolic and ethanolic extracts antimicrobial activity of the medicinal plant Mentha rotundifolia L. against pathogenic strains. The Follin-Cioacalteu method was used to determine the total polyphenols, while the flavonoids were estimated according to the colorimetric method with aluminum chloride. In addition, the determination of condensed tannins is performed by the vanillin method. The antimicrobial activity is tested on five pathogenic bacterial strains, two of which are Gram-negative (Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853), three Gram-positive (Bacillus cereus ATCC 11778, Staphylococcus aureus ATCC 25923 and Micrococcus leutus ATCC 4698), and one yeast (Candida albicans ATCC 26790), by the diffusion on solid medium and microdilution methods. The ethanolic extract of round leaf mint from the Bechar region is very rich in polyphenols and flavonoids (401.75 ± 0.32 mg GAE/g, 549.75 ± 1.23 mg QE/g) compared to the methanolic and hydroalcoholic extracts of this plant from the Sidi-Bel-Abbes region. The results of the obtained well method showed that all bacterial strains exhibited sensitivity to the ethanolic extract of Mentha rotundifolia L. from the Bechar region, with inhibition zones up to 21,67 ± 0,57 mm and minimum inhibitory concentrations (MIC) varying between 06.25 mg/ml and 100 mg/ml, The effect of the other extracts on the tested strains was less significant, the methanolic extract was the least effective. These results demonstrate that the Mentha rotundifolia L. ethanolic extract has a great potential of secondary metabolites with antimicrobial activity. [ABSTRACT FROM AUTHOR]