Effective Antiviral Activity of Tea Tree and Lemon Essential Oils against Influenza A virus (H1N1), Herpes Simplex virus Type 2 and Adenovirus Type 40

Since drug-resistant mutations continue to arise, there are currently few effective therapeutic medicines for the control of the influenza virus, herpes simplex type 2, and adenovirus. In this study, we assessed the potential antiviral effects of the lemon and tea oils. For this purpose, Gas Chromatography-Mass Spectrometry (GC-MS) was used to determine the composition of the essential oils (EOs) for lemon and tea tree. The oils were put through a virucidal test to check for cytotoxicity and in vitro inhibitory action against the H1N1, HSV-2, and Adenovirus (ADV) type 40. The obtained results showed that the dominant compounds in tea tree EO were terpinen-4-ol (62.51%), and in lemon EO, citral (51.9%) and neral (39.43%). Among the analyzed EOs, lemon essential oil is more powerfully antiviral than tea essential oil against the viruses under study compared with the recommended therapies. The lemon essential oil has a high activity (IC50 values of 2.501, 9.677, and 10.488) against H1N1, HSV-2, and ADV, respectively. On the other hand, the tea tree essential oil showed a moderate activity against H1N1 and HSV-2 with IC50 values (28.76, 39.462, respectively) and a high activity against (ADV) with IC50 (39.462). Both essential oils have a selectivity index (SI=IC50/MIC) higher than 4, which is considered effective and safe for the host cell. Therefore, lemon and tea essential oils could be a new natural source of antivirals with potential therapeutic benefits for people suffering from influenza, herpes simplex type 2, and adenovirus, and possibly other membrane-containing viruses.