Antibacterial activity of two endemic Lebanese medicinal plants, Origanum libanoticum and Berberis libanotica, on human pathogenic bacteria

Abstract

The alarming spread of antimicrobial resistance has enticed researchers to search for new effective antimicrobial compounds from natural products. In this study, two plants endemic to Lebanon, Origanum libanoticum and Berberis libanotica, were selected due to their numerous uses in traditional medicine. Methanolic extracts were prepared from plant aerial parts and the chemical composition was analyzed by Gas Chromatography and Mass Spectrometry (GC–MS). Origanum libanoticum exhibited a strong antibacterial activity against Staphylococcus aureus (Minimum Inhibitory Concentration (MIC) 1.56–12.5 mg/mL), Escherichia coli (MIC 1.56–25 mg/mL), Pseudomonas strains (MIC 6.25–25 mg/mL), Klebsiella strains (MIC 3.12–25 mg/mL) and the lowest antibacterial activity was against Acinetobacter strains (MIC between 3.12 and 50 mg/mL). Similarly, B. libanotica showed a strong antimicrobial activity against Staphylococcus strains (MIC 1.56-6.25 mg/mL), E. coli (MIC 0.78-6.25 mg/mL), Klebsiella strains (MIC 0.78-6.25 mg/mL) and Pseudomonas strains (MIC 1.56–12.5 mg/mL). The methanolic extracts showed strong scavenging activity at 0.5 mg.mL⁻¹. Berberis libanotica was further fractionated with solvents of different polarity. MICs ranged between 0.47 and 7.5 mg/mL for different fractions tested. Both extracts exhibit a promising antibacterial activity. More work is needed to identify the active compound(s).

Keywords:

• Origanum libanoticum
• Berberis libanotica
• antibacterial activity
• minimum inhibitory concentration
• DPPH scavenging activity

Disclosure statement

No potential conflict of interest was reported by the authors.

Author’s contribution

Lynn Darwich, Sabah El-Sawalhi, Omar M. Hamzeh: Contributed to the experimental work and the writing of the manuscript draft. Marc El Beyrouthy: Contributed to plant identification, GC–MS analysis, and critical reading of the manuscript. Roula M. Abdel-Massih: Contributed to the design of the study, supervised the laboratory work, writing and critical reading of the manuscript.