In vitro antimicrobial, antioxidant and anti-inflammatory evaluation of Eucalyptus globulus essential oil

Abstract

Eradication of Propionibacterium acnes and associated skin pathogenic species such as Staphylococcus aureus and S. epidermidis
involve anti-oxidant as well as anti-inflammatory effects besides antimicrobial action. For this purpose, Pharmacopoeia Grade (PhEur)
Eucalyptus globulus essential oil was evaluated against the human pathogenic species such as P. acnes ATCC 6919, P. acnes ATCC
11827, S. aureus ATCC 6538 and S. epidermidis ATCC 12228 using an in vitro microdilution method. The composition and quality of
the essential oil was confirmed both by GC/FID and GC/MS techniques, respectively. The in vitro radical-scavenging activity was
evaluated using the photometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assay; the anti-inflammatory activity assay performed
by using the in vitro lipoxygenase (5-LOX) enzyme inhibition assay. Essential oil analysis confirmed the presence of 1,8-cineole (80.2
%), p-cymene (6.6 %), and limonene (5 %) as main components. The antibacterial performance of the tested oil was more susceptible
against Staphylococcus species (MIC=625 µg/mL) compared to P. acnes (MIC=1250 µg/mL). 5-LOX inhibitory activity was determined
as IC50 = 58 ±1,4 µg/mL for the essential oil, compared to the inhibition of the standard nordihydroguaiaretic acid = NDGA. The
preliminary experimental results suggest that the Eucalyptus essential oil and its major constituent 1,8-cineole acts against skin
pathogenic bacteria as a mild natural antimicrobial with anti-inflammatory effects, for further potential topical applications.