# Exploitation of the Antibacterial Activity of Micromeria graeca L. Extracts From Northern Morocco

## TL;DR

This study shows that extracts from the plant Micromeria graeca, especially a methanolic ultrasound-assisted extract, can effectively kill Proteus mirabilis bacteria.

## Contribution

The novel contribution is identifying the most effective extraction method and confirming the antibacterial mechanism of M. graeca extracts against P. mirabilis.

## Key findings

- The methanolic ultrasound-assisted extract (MGME-UAE) showed the strongest antibacterial activity against Proteus mirabilis.
- Sagerinic acid, 5-caffeoylquinic acid, and caffeic acid were identified as major bioactive compounds in MGME-UAE.
- MGME-UAE caused membrane permeability changes and cellular content leakage in bacteria, confirmed by SEM.

## Abstract

Micromeria graeca L. is an aromatic plant rich in bioactive molecules with potential antimicrobial properties. This study evaluated the antibacterial activity of extracts obtained using different solvents and extraction techniques. Among the tested samples, the methanolic ultrasound‐assisted extract (MGME‐UAE) exhibited the strongest bactericidal effect, selectively inhibiting Proteus mirabilis (inhibition zone 12.7 ± 0.6 mm; minimum inhibitory concentration [MIC] = 6.25 mg/mL). Liquid chromatography coupled with photodiode‐array and electrospray ionization–mass spectrometry (LC–PDA/ESI–MS) profiling revealed sagerinic acid (30.37 ± 0.70 mg/g), 5‐caffeoylquinic acid, and caffeic acid as major constituents. Mechanistic assays showed that MGME‐UAE increased membrane permeability, causing significant leakage of DNA/RNA and proteins, which was further confirmed by scanning electron microscopy (SEM) visualization of cell wall disruption. These findings highlight M. graeca as a promising source of natural antibacterial agents, particularly against P. mirabilis.

Among the various extraction techniques investigated, the methanolic ultrasound‐assisted extract (MGME‐UAE) of Micromeria graeca L exhibited the strongest bactericidal effect, selectively inhibiting Proteus mirabilis (inhibition zone 12.7 ± 0.6 mm; MIC = 6.25 mg/mL). Sagerinic acid (30.37 ± 0.70 mg/g), 5‐caffeoylquinic acid, and caffeic acid, were determined by LC‐PDA/ESI‐MS as the major constituents. MGME‐UAE increased membrane permeability, causing significant leakage of DNA/RNA and proteins.