New insight into antimicrobial activities of Linaria ventricosa essential oil and its synergetic effect with conventional antibiotics

Arch Microbiol. 2021 Sep;203(7):4361-4366. doi: 10.1007/s00203-021-02391-7. Epub 2021 Jun 11.

Abstract

The purpose of the present study was to determine for the first time the volatile constituents, the antioxidant and antimicrobial activities of the essential oil (EO) of the endemic Moroccan Linaria ventricosa, alone or in combination with four known antibiotics. The major constituents were 2-methoxy-4-vinylphenol (17.4%), α-terpinene (13.64%) and 3,5-dimethylphenyl isocyanate (12.21%). The EO had moderate antioxidant potency, as measured by DPPH free radical scavenging (1.233 ± 0.031 mg/mL), ferric reducing antioxidant power assay (0.373 ± 0.019 mg/mL) and β-carotene/linoleic acid (0.922 ± 0.026 mg/mL). EO showed microbicidal activity against all microorganisms tested. The highest effectiveness was recorded against Candida albicans (IZ = 24 mm, MIC = 4.87 mg/mL and MMC = 9.75 mg/mL) and Candida glabrata (IZ = 22 mm, MIC = MMC = 4.87 mg/mL). Gram negative bacteria were the most resistant (MIC = MMC = 39 mg/mL). The combination of EO at sub-inhibitory concentrations with antibiotics showed a significant decrease in their individual MICs from 2 to 128 fold, being the best for ciprofloxacin and fluconazole against E. coli and C. albicans and C. glabrata, respectively.

Keywords: Antibiotics; Antioxidant and antimicrobial activities; Chemical composition; Essential oil; Linaria ventricosa; Moroccan endemic plant; Synergistic effect.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Antioxidants* / pharmacology
  • Candida albicans* / drug effects
  • Candida glabrata* / drug effects
  • Drug Synergism
  • Escherichia coli* / drug effects
  • Linaria* / chemistry
  • Microbial Sensitivity Tests
  • Oils, Volatile* / pharmacology

Substances

  • Anti-Bacterial Agents
  • Antioxidants
  • Oils, Volatile