An aqueous extract of fragrant sumac (Rhus aromatica Aiton), a classic uro-therapeutic phyto-medicine, showed dual mode of action against herpes simplex virus type 1 (HSV-1) and a high safety profile

Despite the clinical proven efficacy of fragrant sumac extracts for the treatment of urological diseases like overactive bladder and bacterial infection associated symptoms, little is found in literature about the mode of antiviral action and safety of this active pharmaceutical ingredient. For cytotoxicity assay and mechanistic investigation we used RC-37 cells (African green monkey kidney cells). The fragrant sumac extract demonstrated a very low cytotoxic activity in vitro with a CC₅₀ (50% cytotoxic concentration) value of 2.7%.

Using a plaque reduction assay, the extract showed a high level of anti-HSV-1 activity with an IC₅₀ (50% inhibitory concentration) value of 0.0005%. In addition, at maximum noncytotoxic concentration (0.25%) plaque formation was significantly reduced by more than 99.9% when HSV-1 was pretreated with the fragrant sumac extract for 1h prior to cell infection. Surprisingly, when host cells were treated with the extract for 1h prior to virus infection, the infectivity of HSV-1 was reduced by 50%. These results suggest that the fragrant sumac extract reveals a dual mode of antiviral action. Some compounds of the fragrant sumac extract may interact not only with the viruses but also with the surface of host cells impairing the ability to adsorb to and penetrate into the host cells.

These findings are consistent with the very few reports of minor undesirable side effects from clinical studies with fragrant sumac extract and support also its use for microbiological associated diseases of urinary tract.