ABSTRACT
Background: Essential oils (EOs) have shown antimicrobial, antioxidant, and antiproliferative activity, which may, alone or in combination with other substances, potentially be used for the development of new drugs. However, their chemical variability, depending on the species, varieties, or geographical origin (among other factors) determines different bioactivities that need to be evaluated. Methods: The antioxidant activity of Corymbia citriodora and eight Eucalyptus species EOs was determined using two different methods: the scavenging ability of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+•) and peroxyl free radicals or oxygen radical absorbance capacity (ORAC). Antibacterial activity was evaluated using the microorganisms Streptococcus pneumoniae (strains D39 and TIGR4), and Haemophilus influenza (strain DSM 9999). The essential oils’ minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was assessed using a microdilution method. The antiproliferative activity was determined using the THP-1 cell line (human acute monocytic leukaemia) with methylthiazolyldiphenyl-tetrazolium bromide assay (MTT). Results:Corymbia citriodora and Eucalyptus viminalis EOs showed the highest ABTS and peroxyl free radical scavenging capacity. Eucalyptus globulus EO showed a high potential to treat Streptococcus pneumoniae infections. Haemophilus influenzae was the respiratory pathogen that showed the highest resistance to all EOs, including tea tree EO. After 96 h of incubation, at 25 μg/mL, Eucalyptus radiata and Eucalyptus viminalis EOs showed highest cytotoxic activity against the THP-1 cell line. Conclusions: Despite their specific bioactivities, no single EO showed simultaneously good antioxidant, antimicrobial, and antiproliferative activity.
ABSTRACT
ABSTRACT INTRODUCTION: In this study, we evaluated the chemical composition of a commercial sample of essential oil from Eucalyptus smithii R.T. Baker and its antifungal activity against Microsporum canis ATCC 32903, Microsporum gypseum ATCC 14683, Trichophyton mentagrophytes ATCC 9533, T. mentagrophytes ATCC 11480, T. mentagrophytes ATCC 11481, and Trichophyton rubrum CCT 5507. METHODS: Morphological changes in these fungi after treatment with the oil were determined by scanning electron microscopy (SEM). The antifungal activity of the oil was determined on the basis of minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values. RESULTS: The compound 1,8-cineole was found to be the predominant component (72.2%) of the essential oil. The MIC values of the oil ranged from 62.5μg·mL−1 to >1,000μg·mL−1, and the MFC values of the oil ranged from 125μg·mL−1 to >1,000μg·mL−1. SEM analysis showed physical damage and morphological alterations in the fungi exposed to this oil. CONCLUSIONS: We demonstrated the potential of Eucalyptus smithii essential oil as a natural therapeutic agent for the treatment of dermatophytosis.
