Abstract

Clinacanthus nutans is a medicinal plant traditionally used for viral infections; however, the influence of extraction methods on its antiviral efficacy remains poorly understood. This study comparatively evaluated the anti-herpes simplex virus type-1 (HSV-1) activity of C. nutans leaf extracts obtained by Soxhlet extraction and fermentation. Antiviral activity was assessed in HSV-1-infected Vero cells using a GFP-based assay across multiple concentrations (0.206–50 µg/mL), together with cytotoxicity evaluation. Both extracts exhibited non-cytotoxic profiles at all tested concentrations. The Soxhlet extract showed moderate antiviral inhibition (18.45–27.15%), with maximal activity at 1.85 µg/mL (27.15%), while the fermented extract demonstrated consistently higher inhibition (22.31–32.08%), reaching a maximum of 32.08% at 50 µg/mL. Although neither extract achieved the ≥50% threshold for classification as an active antiviral agent, fermentation clearly enhanced antiviral performance compared with Soxhlet extraction. These findings indicate that extraction strategy significantly influences the biological activity of C. nutans and highlight fermentation as a promising bioprocessing approach to enhance its antiviral potential, providing a foundation for further phytochemical characterization and bioactivity-guided compound isolation