Oil-in-water emulsion formulated with eucalyptus leaves extract inhibit influenza virus binding and replication in vitro

Throughout human history, the human-beings have been used different types of plants as antimicrobial agents in fight against infectious diseases. Influenza virus is one of the most common causes of respiratory infection and transmitted through direct contact with flu infected individuals and contaminated substances or droplets. In the current study, both oil-in-water and water-in-oil emulsions with hydroalcoholic extract of eucalyptus leaves (OLHE) were developed and their antiviral efficiency was evaluated. To doing so, Madin-Darbey Canine Kidney (MDCK) cells were treated with effective minimal cytotoxic concentration of the formulated emulsions. The treated cells were then infected with 50% cell culture infectious dose (100 CCID(50)) of the A/H1N1 virus (the swine flu). The viral titers were measured by hemagglutination (HA) and cell culture infectious dose 50% (CCID(50)) assays. Also, to check the virus binding inhibition via the formulated extract, the viruses were incubated with the formulated extracts. Our study showed that the oil-in-water emulsions formulated with 2% eucalyptus leaves extract inhibited virus replication completely when the cells were infected by 100 CCID(50) and decreased HA titer up to four fold. Therefore, this formulation, may hold promising application to prevent influenza virus transmission through direct contact among children and passengers.