Liposome-incorporated Santolina insularis essential oil: Preparation, characterization and in vitro antiviral activity

The effect of liposomal inclusion on the stability and in vitro antiherpeti c activity of Santoliua insularis essential oil was investigated. In order to study the influence of vesicle structure on the liposome properties, mul tilamellar and unilamellar vesicles were prepared by the film method and so nication, respectively. Vesicles were obtained from hydrogenated soya phosp hatydilcholine and cholesterol. Formulations were examined for their stabil ity for over one year monitoring the drug leakage from vesicles and the ave rage size distribution. The stability of the incorporated oil was verified by studying its quali-quantitative composition. The antiviral activity was studied against Herpes simplex virus type 1 (HSV-1) by plaque reduction and yield reduction assays. Results showed that Santolina insularis essential oil can be incorporated in high amounts in the prepared liposomes, which su ccessfully prevented its degradation. Moreover, stability studies pointed o ut that vesicle dispersions were stable for at least one year and neither o il leakage nor vesicle size alteration occurred during this period. Antivir al activity assays demonstrated that Santolina insularis essential oil is e ffective in inactivating HSV-1 and that the activity is principally due to direct virucidal effects. Free essential oil proved to be more effective th an liposomal oil and a different activity was discovered which related to t he vesicular structure. The EDS values, significantly lower when cells were pre-incubated with the essential oil before the virus adsorption, indicate an intracellular mechanism in the antiviral activity of Santolina insulari s. Moreover, liposomal Santolina essential oil is non toxic in the range of the concentration tested.