Received: 25 June 2013; in revised form: 18 July 2013 / Accepted: 19 July 2013 / Published: 9 August 2013
Abstract: Influenza virus causes high morbidity among the infected population annually and occasionally the spread of pandemics. Melaleuca alternifolia Concentrate (MAC) is an essential oil derived from a native Australian tea tree. Our aim was to investigate whether MAC has any in vitro inhibitory effect on influenza virus infection and what mechanism does the MAC use to fight the virus infection. In this study, the antiviral activity of MAC was examined by its inhibition of cytopathic effects. In silico prediction was performed to evaluate the interaction between MAC and the viral haemagglutinin. We found that when the influenza virus was incubated with 0.010% MAC for one hour, no cytopathic effect on MDCK cells was found after the virus infection and no immunofluorescence signal was detected in the host cells. Electron microscopy showed that the virus treated with MAC retained its structural integrity. By computational simulations, we found that terpinen-4-ol, which is the major bioactive component of MAC, could combine with the membrane fusion site of haemagglutinin. Thus, we proved that MAC could prevent influenza virus from entering the host cells by disturbing the normal viral membrane fusion procedure.
Keywords: Melaleuca alternifolia Concentrate (MAC); influenza virus; haemagglutinin; terpinen-4-ol; molecular docking; molecular dynamics
The effect of TTO on acidification of cellular lysosomes was studied by vital staining with acridine orange using bafilomycin A1 as positive control. The treatment of cells with 0.01% (v/v) of TTO at 37 °C for 4 h before staining inhibited the acridine orange accumulation in acid cytoplasmic vesicles, indicating that TTO could inhibit viral uncoating by an interference with acidification of intralysosomal compartment.
Additionally, the present study evaluated the antiviral activity
of essential oil in aerosol form. Reasonably, the more effective TTO was used in such kind of evaluation. As was found in aerosol form, the TTO possessed the strong antiviral action as well as on the filter surface. The concentration of aerosolized virus in all experiments was kept at the maximum possible level, which was achieved by relatively high virus titer in the initial suspension prepared for aerosolization (∼107.5/mL). Use of heavily concentrated bioaerosol stream enabled acquisition of more than 103 virions by 1 mL of the collecting liquid (varied slightly in different experiments), which provides opportunities for evaluation of the process efficiency within three orders of magnitude, enabling to identify the inactivation efficiency at the level above 99.5%. These findings look very promising for the implementation of such aromatic substances in filtration
applications to control the harmful bioaerosols, and further improvement of theindoor air quality. Such type of essential oils could be successfully utilized
as effective disinfectant against of broad range of microorganisms as well in aerosol form as in form of filter coating substance.