Punica granatum Peel and Leaf Extracts as Promising Strategies for HSV-1 Treatment

Punica granatum is a rich source of bioactive compounds which exhibit various biological effects. In this study, pomegranate peel and leaf ethanolic crude extracts (PPE and PLE, respectively) were phytochemically characterized and screened for antioxidant, antimicrobial and antiviral activity. LC-PDA-ESI-MS analysis led to the identification of different compounds, including ellagitannins, flavonoids and phenolic acids. The low IC(50) values, obtained by DPPH and FRAP assays, showed a noticeable antioxidant effect of PPE and PLE comparable to the reference standards. Both crude extracts and their main compounds (gallic acid, ellagic acid and punicalagin) were not toxic on Vero cells and exhibited a remarkable inhibitory effect on herpes simplex type 1 (HSV-1) viral plaques formation. Specifically, PPE inhibited HSV-1 adsorption to the cell surface more than PLE. Indeed, the viral DNA accumulation, the transcription of viral genes and the expression of viral proteins were significantly affected by PPE treatment. Amongst the compounds, punicalagin, which is abundant in PPE crude extract, inhibited HSV-1 replication, reducing viral DNA and transcripts accumulation, as well as proteins of all three phases of the viral replication cascade. In contrast, no antibacterial activity was detected. In conclusion, our findings indicate that Punica granatum peel and leaf extracts, especially punicalagin, could be a promising therapeutic candidate against HSV-1.