Aims:  To investigate the in vitro antiviral activity of Melaleuca alternifolia essential oil (TTO) and its main components, terpinen‐4‐ol, α‐terpinene, γ‐terpinene, p‐cymene, terpinolene and α‐terpineol. Methods and Results:  The antiviral activity of tested compounds was evaluated against polio type 1, ECHO 9, Coxsackie B1, adeno type 2, herpes simplex (HSV) type 1 and 2 viruses by 50% plaque reduction assay. The anti‐influenza virus assay was based on the inhibition of the virus‐induced cytopathogenicity. Results obtained from our screening demonstrated that the TTO and some of its components (the terpinen‐4‐ol, the terpinolene, the α‐terpineol) have an inhibitory effect on influenza A/PR/8 virus subtype H1N1 replication at doses below the cytotoxic dose. The ID50 value of the TTO was found to be 0·0006% (v/v) and was much lower than its CD50 (0·025% v/v). All the compounds were ineffective against polio 1, adeno 2, ECHO 9, Coxsackie B1, HSV‐1 and HSV‐2. None of the tested compounds showed virucidal activity. Only a slight virucidal effect was observed for TTO (0·125% v/v) against HSV‐1 and HSV‐2. Conclusions:  These data show that TTO has an antiviral activity against influenza A/PR/8 virus subtype H1N1 and that antiviral activity has been principally attributed to terpinen‐4‐ol, the main active component. Significance and Impact of the Study:  TTO should be a promising drug in the treatment of influenza virus infection.

Hydroxytyrosol and dihydrocaffeoyl catechols with lipophilic properties have been synthesized in high yield using tyrosinase immobilized on multi-walled carbon nanotubes by the Layer-by-Layer technique. All synthesized catechols were evaluated against a large panel of DNA and RNA viruses, including Poliovirus type 1, Echovirus type 9, Herpes simplex virus type 1 (HSV-1), Herpes simplex virus type 2 (HSV-2), Coxsackievirus type B3 (Cox B3), Adenovirus type 2 and type 5 and Cytomegalovirus (CMV). A significant antiviral activity was observed in the inhibition of HSV-1, HSV-2, Cox B3 and CMV. The mechanism of action of the most active dihydrocaffeoyl derivative was investigated against a model of HSV-1 infection.

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