Inhibition of herpes simplex virus type 1 infection by Sambucus ebulus extract in vitro

The emergence of drug-resistant strains of herpes simplex virus type 1 (HSV-1) has been increasingly reported. Therefore, attempts to discover new antiviral agents in particular from natural compounds are required. In this study, we evaluated the possible inhibitory effects of hydroalcoholic extract of Sambucus ebulus (S. ebulus) against HSV-1.

S. ebulus extract was produced by maceration method. MTT assay was used to evaluate the cytotoxicity effects of the S. ebulus extract; also, antiviral effects were measured both by test TCID50 and quantitative real-time PCR methods. To study the inhibitory impact of S. ebulus extract on the expression of HSV-1 antigens, indirect immunofluorescence assay (IFA) was also performed.  All analyses were performed using the GraphPad Prism software v. 7.0.

In the postexposure assay of HSV-1 with S. ebulus extract at the highest nontoxic concentration (75 μg/mL), S. ebulus extract led to 2.6 log10 TCID50 reduction in infectious virus titer. At the highest nontoxic concentration, the S. ebulus extract led to inhibition rates of 91.2%, based on the quantitative real-time PCR assay results (p<0.001). Also, in the immunofluorescence assay, a significant reduction was observed in fluorescence emission intensity in HSV-1-infected cell treated with S. ebulus extract compared to the control group.

S. ebulus extract is a novel and effective natural compound in reducing HSV-1 titer and future studies should be conducted to discover the complete mechanism of antiviral effect of this natural compound.