Supercritical fluid extraction as an alternative process to obtain antiviral agents from thyme species

• The antiviral properties of supercritical CO2 extracts obtained from three thyme species were evaluated against the herpes simplex virus type 1.
• These supercritical extracts mainly inhibit HSV-1 intracellular replication, although they are also able to disrupt virus attachment step.
• Thymus zygis supercritical extract was more effective than the other thyme species extracts tested.
• The highest activity found in T. zygis extract could be related to the highest amount of thymol, carvacrol and borneol presented in this extract.
• Supercritical extraction was an alternative technique to obtain antiviral extracts from thyme species.

The antiviral properties of supercritical CO2 extracts obtained from thyme species (Thymus vulgaris, Thymus hyemalis and Thymus zygis) were evaluated against the herpes simplex virus type 1 (HSV-1) at different stages during virus infection. Results indicated that when cells were pre-treated with the thyme extracts, an important reduction of virus infectivity was achieved; being T. zygis extract more effective than the other thyme species extracts. Comparing data obtained during the adsorption stage with those found in the pre-treatment step, at the same concentration, the reduction of the virus infectivity was increased by 30%, indicating that extracts were more effective when applied during adsorption period. Moreover, supercritical extracts of thyme species were able to significantly inhibit the in vitro virus replication, showing IC50 values among 1.74–2.25 μg/mL. A GC–MS characterization of supercritical extracts was carried out in order to identify the type of compounds responsible for the antiviral activity. Thus, the higher antiviral activity found in T. zygis supercritical extract, could be related to the higher percentage of thymol, carvacrol and borneol (79.77%) presented in this extract.Supercritical fluid extraction represents an alternative method to obtain antiviral extracts from Thymus species. These supercritical extracts mainly inhibit HSV-1 intracellular replication, although they were also able to disrupt the virus attachment step.