Antiviral activity of selected plant-derived polyphenols against Varicellovirus bovinealpha1 (BoAHV-1).

Medicinal plants have been used for centuries in traditional practices to treat a wide range of ailments, including viral infections. Phytochemicals found in these plants represent a promising and largely untapped resource for the development of novel antiviral agents, particularly in light of the limited availability of effective antiviral therapies. This study aimed to evaluate the antiviral potential of five polyphenolic compounds commonly found in medicinal plants: quercetin, rutin, baicalein, (-)-epicatechin, and ethyl gallate against bovine alphaherpesvirus type 1 (BoAHV-1), used as a model for the Orthoherpesviridae family. The cytotoxicity and antiviral activity of the compounds were assessed in vitro using the colorimetric MTT assay. Antiviral effects were quantified based on the concentration required to inhibit 50% of viral replication (IC₅₀). Compounds were tested individually and in combination, with treatments applied before, during, and after viral infection. Expression of the viral gB gene was evaluated using RT-qPCR. Quercetin, rutin, and baicalein exhibited notable antiviral activity, with IC₅₀ values of 16.8 µg mL⁻¹, 21.4 µg mL⁻¹, and 26.4 µg mL⁻¹, respectively, and high selectivity indices (> 15.4, 10.0, and 8.0). In contrast, (-)-epicatechin and ethyl gallate showed no measurable antiviral effect (IC₅₀ > 256 µg mL⁻¹). Combinatorial treatments revealed significant synergistic effects. All active compounds reduced gB gene expression, regardless of the timing of treatment. The results support the antiviral potential of certain plant-derived polyphenols, both alone and in synergy, underscoring their promise as candidates for the development of novel antiviral therapies targeting herpesviruses.