Modulatory effects of Eucalyptus spp. essential oils and eucalyptol on cytokines and antiviral activity against SARS-CoV-2

The ongoing challenge of SARS-CoV-2 and its evolving variants highlights the need for new therapeutic strategies to address viral replication and the inflammatory complications associated with COVID-19. This study aimed to investigate the biological effects of essential oils from Eucalyptus staigeriana, Eucalyptus exserta, Eucalyptus leptophleba and eucalyptol, against SARS-CoV-2 and COVID-19 complications. Essential oils were extracted from leaves by steam distillation, while eucalyptol was commercially obtained. The chemical composition was analyzed using gas chromatography-mass spectrometry. In vitro experiments assessed the cytotoxicity and antiviral activity of essential oils and eucalyptol. Inflammatory cytokines were quantified by flow cytometry. The essential oils yielded 3.59% (E. staigeriana), 0.79% (E. exserta), and 0.32% (E. leptophleba). Common major constituents included α-pinene, (-)-β-pinene, o-cymene, D-limonene, eucalyptol, γ-terpinene, and terpinolene. Antiviral assays showed that none of the essential oils or eucalyptol inhibited SARS-CoV-2 at non-cytotoxic concentrations. However, significant modulation of pro-inflammatory cytokines was observed. E. staigeriana exhibited the most effective regulation of IL-6 levels. Additionally, both essential oils and eucalyptol controlled MCP-1 and CXCL10 levels. All treatments maintained low IL-8 levels, except for E. leptophleba. These findings suggest that eucalyptus-derived compounds could offer therapeutic benefits in managing COVID-19-related inflammation.