Nigella sativa essential oil and its bioactive compounds as resistance modifiers against Staphylococcus aureus

Phytother Res. 2019 Apr;33(4):1010-1018. doi: 10.1002/ptr.6294. Epub 2019 Jan 23.


Nigella sativa essential oil (EO) and its compounds (thymoquinone, carvacrol, and p-cymene) have a broad antimicrobial spectrum. The aim of this study was to investigate the antimicrobial and resistance modifying activity of N. sativa EO, thymoquinone, carvacrol, and p-cymene against one methicillin susceptible and one methicillin resistant Staphylococcus aureus strain. N. sativa EO, thymoquinone, carvacrol, and p-cymene were assessed for antimicrobial activity and modulation of antimicrobial resistance (by broth microdilution), inhibition of antimicrobial efflux (by ethidium bromide [EtBr] accumulation assay), relative expression of mepA gene (by real-time reverse transcriptase quantitative polymerase chain reaction), membrane disrupting effect (by LIVE/DEAD BacLight™ Kit), and finally antibiofilm activity (by the crystal violet assay). Both strains of S. aureus were susceptible to N. sativa EO, thymoquinone, and carvacrol. N. sativa EO and carvacrol induced the increase of EtBr accumulated by both S. aureus strains. Membrane integrity of ATCC strain was disrupted by carvacrol and p-cymene, whereas for the methicillin resistant S. aureus (MRSA) strain the membrane integrity was disrupted by each compound. N. sativa EO and its bioactive compounds such as carvacrol and p-cymene could be applied as resistance modifiers in MRSA strains.

Keywords: Nigella sativa essential oil; Staphylococcus aureus; antibacterial; biofilm; efflux pump inhibitor (EPI).

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Anti-Infective Agents / pharmacology
  • Benzoquinones / pharmacology
  • Biofilms / drug effects
  • Cymenes
  • Drug Resistance, Multiple, Bacterial / drug effects*
  • Methicillin-Resistant Staphylococcus aureus / drug effects*
  • Methicillin-Resistant Staphylococcus aureus / physiology
  • Microbial Sensitivity Tests
  • Monoterpenes / pharmacology
  • Nigella sativa / chemistry*
  • Oils, Volatile / pharmacology*
  • Plant Extracts / pharmacology
  • Staphylococcal Infections / drug therapy
  • Staphylococcal Infections / microbiology
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / physiology


  • Anti-Bacterial Agents
  • Anti-Infective Agents
  • Benzoquinones
  • Cymenes
  • Monoterpenes
  • Oils, Volatile
  • Plant Extracts
  • 4-cymene
  • carvacrol
  • thymoquinone