Combination effect of three anti-HSV-2 active plant extracts exhibiting different modes of action

The emergence of multidrug-resistant viruses leads to discover a novel source of drugs or a new strategy to overcome this obstacle. Combined herbal therapies are becoming a promising approach for a better efficiency. In this study, Pistacia lentiscus and Peganum harmala were investigated for their anti HSV-2 activity. Twenty eight organic extracts from different organs were evaluated for their cytotoxicity on Vero cells and their anti HSV-2 activity using the MTT test and the plaque reduction assay, respectively. Peganum harmala methanol seeds extract, Pistacia lentiscus methanol stem and dichloromethane fruit extracts were active on HSV-2 with selectivity index values of 13.19, 51.23 and 10.23, respectively. These active extracts exhibited different mode of action: (1) Peganum harmala methanol seeds extract showed a virucidal action before virus adsorption and penetration, and on the newly formed virions before their release outside infected cells—(2) Pistacia lentiscus methanol stem extract exhibited virucidal effect only before virus adsorption and penetration—(3) Pistacia lentiscus dichloromethane fruit extracts demonstrated virus inhibition up to 7 h post infection. The binary combination of the three active extracts did not improve their individually activity. This report could contribute to prove that combination of active extracts do not necessary increase the initial activity.