Abstract

Olea europeae (L.) has been reported to have antibacterial, antifungal and antiviral activities. The aim of the present study is to evaluate antiviral activity of olive leaves extract (OLE) against herpes simplex viruses (HSV) type-1 virus. Screening of antiviral activity was assessed by measuring inhibition of viral-induced cytopathic effect of in vero cells of different OLE fractions that have been successively extracted using solvents of increasing polarities, against HSV type-1 virus. Negligible antiviral activity has been shown of different fractions, except for ethyl acetate and n-butanol fractions, showing strong and moderate anti-HSV type -1 activity, respectively. High performance liquid chromatography (HPLC) chromatographic analysis of both fractions revealed high oleuropein content in ethyl acetate fraction in addition to other phenolic and flavonoid contents, whereas n-butanol fraction showed only high content of other phenolic and flavonoid compounds. Cytotoxicity of ethyl acetate fraction was assessed in vero cell line, the mean cytotoxic concentration CC50, was reported to be 610 µg/ml. On the other hand, the 50% inhibitory concentration (IC50), against HSV-1, was of value as low as 40 µg/ml (SI = 15.2). This concentration could be more reduced to 33 µg/ml (SI = 16.9); that is, 17% reduction in dose, by formulating a microemulsion dosage form, with particle size of 13 to 19 nm, being assessed by Malvern Zetasizer Ver. 6.2 and electron microscopy. Acyclovir, a recommended anti-HSV agent, was used as a positive control. Oleuropein pure standard and the main phenolic component of OLE, was also assessed for its anti-HSV type-1 virus. As conclusion, microemulsion formulation enhanced antiviral activity of crude OLE.

Key words: Olive leaves extract, OLE, acyclovir, anti-HSV activity, microemulsion, oleuropein.