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Melaleuca alternifolia Essential Oil Inhibited Influenza A Virus Replication
Melaleuca alternifolia Essential Oil Inhibited Influenza A Virus Replication
Nader Ebrahimi,1,*Hadi Razavi Nikoo,2Fatemeh Fotohi,3Parvaneh Mehrbod,4Hosnieh Sokandan,5Sahar Bathaeyan,6
1. Department of Microbiology, Golestan University of Medical Sciences, Gorgan, Iran - Influenza and Respiratory Viruses Dept., Pasteur Institute of Iran, Tehran, Iran 2. Golestan University of Medical Sciences 3. Influenza and other Respiratory Viruses Dept, Pasteur Institute of Iran 4. Influenza and other Respiratory Viruses Dept, Pasteur Institute of Iran 5. Influenza and other Respiratory Viruses Dept, Pasteur Institute of Iran 6. Influenza and other Respiratory Viruses Dept, Pasteur Institute of Iran
Introduction: Influenza A virus (IAV) poses an ongoing threat to global health due to its high transmissibility and potential for severe respiratory disease. The emergence of drug-resistant IAV strains highlights the urgent need for alternative antiviral agents. Melaleuca alternifolia (tea tree), a plant native to Australia and traditionally used by Aboriginal communities, produces an essential oil rich in monoterpenes such as terpinen-4-ol. Tea tree oil has shown broad-spectrum antimicrobial effects and emerging evidence supports its antiviral activity against enveloped viruses, including IAV, HSV, and coronaviruses. Its mechanisms may involve disruption of viral envelopes and modulation of host responses. These properties position M. alternifolia essential oil as a promising candidate for further antiviral research.
Methods: MDCK cells were cultured in DMEM with 10% FBS. Influenza A (H1N1) virus was propagated and titrated by TCID₅₀ assay. Melaleuca alternifolia essential oil was diluted in DMSO (≤0.1%) and tested for cytotoxicity using MTT assay to determine CC₅₀ and NCTC. Antiviral effects were evaluated under pre-, co-, and post-treatment conditions using HA assay, TCID₅₀, and real-time PCR. A time-of-addition assay was conducted to assess the timing of antiviral action.
Results: In this study, the essential oil of Melaleuca alternifolia (TTEO) demonstrated significant antiviral activity against influenza A virus (H1N1). The CC₅₀ of TTEO was obtained at 1.441 mg/mL, indicating a higher safety profile compared to standard antiviral drugs amantadine and oseltamivir. The selectivity index (SI) of TTEO was also higher, emphasizing its relative safety and effectiveness. Antiviral assays showed that TTEO was most effective in the pre-treatment phase, completely inhibiting viral replication. These findings were supported by reduced viral titers (TCID₅₀), lower HA activity, and significant decreases in viral RNA copy numbers, especially in early exposure stages, highlighting TTEO’s potential as a safe and effective natural antiviral agent.
Conclusion: In conclusion, the essential oil of Melaleuca alternifolia (TTEO) demonstrated notable antiviral efficacy against H1N1 influenza virus, significantly reducing viral load, HA activity, and RNA copy numbers. With a higher safety margin (CC₅₀ = 1.441 mg/mL) and selectivity index compared to standard antiviral drugs like amantadine and oseltamivir, TTEO showed promise as a natural and effective antiviral candidate. These findings support its potential for further development in antiviral therapies.