Evaluation of the Antiviral Activity of Convolvulus spicatus Methanolic Extract Against Herpes Simplex Virus Type 1 in Vero Cells

The cumulative emergence of viral resistance and the limitations of conventional antiviral therapies have stimulated considerable attention to natural products as alternative antiviral agents. Plant-derived bioactive compounds could offer promising therapeutic options with lower cytotoxicity. Convolvulus spicatus is a medicinal plant with various pharmacological activities; however, its antiviral potential is poorly investigated. The aim of this study was to evaluate the in vitro antiviral activity of C. spicatus methanolic extract against herpes simplex virus Type 1 (HSV-1) in Vero cells and to determine its effects on cell viability, apoptosis, necrosis, and cell-cycle progression. The methanolic extract of C. spicatus was prepared by the Soxhlet extraction method. The cytotoxicity and antiviral activities were measured by MTT assay in HSV-1-infected Vero cells. The viral load of the HSV-1 glycoprotein D gene was determined using quantitative real-time PCR. Cell-cycle distribution, including the pre-G1 population, was analyzed by flow cytometry with propidium iodide (PI) staining. Early apoptosis, late apoptosis, and necrosis were measured by flow cytometry with Annexin V-FITC/PI staining after treatment with the extract at the maximum non-toxic concentration (625 µg/mL). The extract showed low cytotoxicity to Vero cells at the highest non-toxic concentration tested. Treatment of HSV-1-infected cells with C. spicatus extract significantly reduced virus-induced cytopathic effects and significantly reduced HSV-1 viral load compared with untreated infected cells. Flow cytometric analysis showed a significant decrease in the pre-G1 population, indicating reduced Deoxyribonucleic Acid (DNA) fragmentation, and decreased early apoptotic, late apoptotic, and necrotic cell populations following treatment. Furthermore, the extract reduced the pre-G1 population and altered the cell-cycle distribution of HSV-1-infected cells. The findings of this work suggest that the methanolic extract of C. spicatus exhibits promising antiviral activity against HSV-1 in vitro by decreasing the viral load, preventing host-cell damage caused by the virus, and reducing virus-induced cellular damage.