Effect of Extracts of Passiflora edulis Leaves on Herpes Viruses

Passiflora edulis (Pe) is considered as a traditional medicinal plant with different therapeutic effects. In the present study we examined, in vitro, the antiviral potential of aqueous and ethanolic leaf extracts of Passiflora edulis on herpes simplex viruses 1 and 2 (HSV-1, HSV2), and on Varicella-Zoster virus (VZV). Viral infection development was evaluated by plaque assay. Our results showed significantly higher antiviral activity of the ethanolic extract against all tested viruses, when compared to the aqueous extract. The 80%-MeOH fraction of the ethanolic extract offered the highest activity against these viruses, with 50% inhibitory concentration (IC50) of 4 ± 0.18, 7 ± 0.30 and 2.3 ± 0.15μg/ml against HSV-1, HSV-2, and VZV respectively, without any significant cytotoxicity. Most prominent antiviral activity was obtained when the 80%-MeOH fraction was added during the infection, or when it was incubated with the virus particles prior to infection. Also, a significant inhibition of the viral infection was obtained when this fraction was added after viral entry into the host cells, probably as a result of a significant delay in the production of infective viral particles inside the infected cells. A synergistic antiviral effect against all tested viruses was also observed when cells were treated with a combination of acyclovir (ACV) and 80%-MeOH fraction of Pe. Further study is required for the isolation and purification of the anti-virally active component/s of this Pe fraction.