Syzygium aromaticum essential oil and its major constituents: Assessment of activity against Candida spp. and toxicity

by Priscilla Guimarães Silva Vasconcelos, Gabriel Flores Abuna, Joanda Paolla Raimundo e Silva, Josean Fechine Tavares, Edja Maria Melo de Brito Costa, Ramiro Mendonça Murata

Syzigium aromaticum essential oil (EO), eugenol, and β-caryophyllene were evaluated regarding antifungal, antibiofilm, and in vitro toxicity. Additionally, in vivo toxicity of EO was observed. Anti-Candida activity was assessed through broth microdilution assay for all compounds. Time-kill assay (0, 1, 10, 30 min, 1, 2, and 4 h) was used to determine the influence of EO and eugenol on Candida Growth kinetics. Thereafter, both compounds were evaluated regarding their capacity to act on a biofilm formation and on mature biofilm, based on CFU/ml/g of dry weight. Cell Titer Blue Viability Assay was used for in vitro cytotoxicity, using oral epithelial cells (TR146) and human monocytes (THP-1). Lastly, Galleria mellonella model defined the EO in vivo acute toxicity. All compounds, except β-cariofilene (MIC > 8000 μg/ml), presented antifungal activity against Candida strains (MIC 500–1000 μg/ml). The growth kinetics of Candida was affected by the EO (5xMIC 30 min onward; 10xMIC 10 min onward) and eugenol (5xMIC 10 min onward; 10xMIC 1 min onward). Fungal viability was also affected by 5xMIC and 10xMIC of both compounds during biofilm formation and upon mature biofilms. LD₅₀ was defined for TR146 and THP1 cells at, respectively, 59.37 and 79.54 μg/ml for the EO and 55.35 and 84.16 μg/ml for eugenol. No sign of toxicity was seen in vivo up to 10mg/ml (20 x MIC) for the EO. S. aromaticum and eugenol presented antifungal and antibiofilm activity, with action on cell growth kinetics. In vivo acute toxicity showed a safe parameter for the EO up to 10 mg/ml.