Study of Phenolic Compounds and Antibacterial Activity of Origanum vulgare ssp. glandulosum

This study investigates the methanolic extraction and biological activities of Origanum vulgare ssp. glandulosum, a medicinal aromatic plant collected in Algeria. The plant material was air-dried, finely ground, and extracted using the Soxhlet technique with methanol (99.7%) as solvent for 6 hours. The resulting extract was filtered, concentrated under reduced pressure at 40 °C, and stored for further analyses.

The antimicrobial activity of the extract was evaluated against several bacterial strains using disk diffusion and microdilution methods. The tested strains included Gram-negative bacteria such as Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Proteus vulgaris, and Acinetobacter baumannii. The results showed inhibition zones ranging from 7 to 9 mm, indicating a moderate antibacterial effect when compared to standard antibiotics, which produced significantly higher inhibition zones.

In parallel, the total phenolic content of the methanolic extract was determined using the Folin–Ciocalteu spectrophotometric method. The assay is based on the reduction of phosphomolybdic–phosphotungstic complexes, resulting in a blue-colored complex measured at 725 nm. The extract exhibited a high phenolic content estimated at 526.75 µg GAE/mg of extract, demonstrating its richness in bioactive secondary metabolites.

Overall, the results highlight that O. vulgare ssp. glandulosum possesses notable antimicrobial potential and a high level of phenolic compounds, suggesting its possible application as a natural source of antioxidant and antibacterial agents in pharmaceutical and therapeutic fields.