In vitro Assessment of the Antiviral Activity of Medicinal Plant Extracts Against Dengue Virus Serotype 2 (DENV-2)

Background: Dengue virus infection remains a significant global health challenge with limited antiviral treatment options. Objective: To evaluate the antiviral potential of selected medicinal plant extracts against dengue virus serotype 2 (DENV-2) through phytochemical screening and in vitro assays. Methodology: This descriptive, in vitro experimental study was conducted over one year (August 2023–July 2024) at the University of Poonch Rawalakot. Ten medicinal plants traditionally used for febrile and viral illnesses in Pakistan were selected and authenticated. Plant extracts were prepared using methanol, ethanol, and aqueous solvents and screened for key phytochemicals including flavonoids, alkaloids, tannins, saponins, and terpenoids. Cytotoxicity on Vero cells was assessed by MTT assay to determine CC₅₀ values. Non-toxic concentrations of extracts were evaluated for antiviral activity against DENV-2 using Plaque Reduction or Virus Yield Reduction Assays. IC₅₀ and Selectivity Index (SI) were calculated. Experiments were conducted in triplicate, and data analyzed using ANOVA with significance at p < 0.05. Results: All plants contained various bioactive compounds; Curcuma longa showed the richest phytochemical profile. Curcuma longa exhibited the highest safety (CC₅₀ = 455 µg/mL) and antiviral efficacy (IC₅₀ = 38.20 µg/mL) with an SI of 11.91 and 82.34% viral inhibition. Andrographis paniculata, Azadirachta indica, Nigella sativa, and Phyllanthus niruri also demonstrated significant antiviral activity with SI values above 6. Dose-dependent viral inhibition was confirmed for these top five extracts. Conclusion: Selected medicinal plants, particularly Curcuma longa, show promising antiviral activity against DENV-2 and merit further investigation for therapeutic development.