Lower respiratory tract infections caused by bacteria and viruses, including the SARS-CoV-2, are associated with severe lung inflammation. The use anti-inflammatory drugs such as the corticosteroids in treating conditions resulting from infection-mediated lung inflammation has been associated with significant side effects. The COVID-19 pandemic has resulted in renewed focus on the use of natural products to treat inflammatory symptoms associated with lower respiratory tract infections. The oil from Eucalyptus globulus is widely reputed for its benefits for treating infections of the upper and lower respiratory tract and has been suggested to have anti-inflammatory actions. Lower respiratory tract infections caused by bacteria and viruses, including the SARS-CoV-2, are associated with severe lung inflammation. The use anti-inflammatory drugs such as the corticosteroids in treating conditions resulting from lung inflammation has been associated with significant side effects. The COVID-19 pandemic has resulted in renewed focus on the use of natural products to treat inflammatory symptoms associated with lower respiratory tract infections. The essential oils from Eucalyptus globulus are widely reputed for its benefits for treating infections of the upper and lower respiratory tract and has been suggested to have anti-inflammatory actions. In this study, the effects of a methanolic extract of Eucalyptus globulus were investigated in interleukin-1β (IL-1β)-induced increase in inflammatory mediator production in A549 lung epithelial cells. These cells were treated with the extract (6.25, 12.5, 25, 50, and 100 µg/ml) followed by stimulation with IL-1β (1 ng/ml) for 24 h) and cell supernatants were collected. The cell viability of IL-1β stimulated A549 cells was determined using the MTT colorimetric assay. Further, the levels of cytokines such as TNF-α, IL-β, IL-6 and IL-8 levels in cell supernatants were measured using the enzyme‐linked immunosorbent assay (ELISA) as described by specific manufacturers. In addition, cell lysates were prepared from IL-1β stimulated A549 cells pre-treated with extract different concentrations and they were used for a determination of NLRP3 and COX-2 protein expression levels. Lastly, GC-MS analysis was applied to identify and quantify the chemical constituents including Eucalyptol, a major component of Eucalyptus globulus. Results showed that pre-treatment of TNF-α-stimulated A549 cells with the extract induced a significant increase in the cell viability, while no significant effect was observed on the cell viability of IL-1β-stimulated A549 cells treated with the extract. Therefore, IL-1β stimulated cells were used in further experiments. It was observed that IL-1β significantly induced inflammation in A549 cells. However, pre-treatment of IL-1β stimulated A549 cells with Eucalyptus globulus methanolic extract reduced the levels of IL-1β, IL-6 and IL-8 in a dose dependent manner. Furthermore, protein levels of NLRP3 and COX-2 in IL-1β stimulated A549 cells were significantly decreased in a dose dependent manner after pre-treatment with the extract. These results suggest that E. globulus methanolic extract reduces inflammation in lung epithelial cells, thus confirming its potential as a source of natural bioactive compounds against inflammatory responses accompanying upper and lower respiratory tract infections. Moreover, the phytochemical analysis of the extract indicated the presence of eucalyptol, β-caryophyllene, α-humulene, azulene, and germacrene D as bioactive compounds which may be responsible for its anti-inflammatory activity.
| Date of Award | 19 May 2026 |
|---|
| Original language | English |
|---|
| Supervisor | Olumayokun Olajide (Main Supervisor) |
|---|