Investigation of Anti‐Chikungunya Activity of Andrographis paniculata Aqueous Extract: A Comparative Study With Green‐Synthesized Silver Nanoparticles

ABSTRACT

Chikungunya virus (CHIKV) presents a major global health challenge with limited therapeutic options, driving the search for eco‐friendly, phytochemical‐based antivirals. This study compared the anti‐CHIKV efficacy of crude Andrographis paniculata aqueous extract and its green‐synthesized silver nanoparticles (AgNPs). AgNPs were successfully produced via bio‐reduction of silver nitrate using the extract. Cytotoxicity assays (MTT) showed the crude extract had a better safety profile with a maximum non‐toxic dose (MNTD) of 62.50 µg/mL compared to 31.25 µg/mL for the AgNPs. The aqueous extract demonstrated significantly greater cytoprotective activity ( p < 0.0001) against CHIKV‐infected Vero cells compared to AgNPs, with cell viability rates of 35.95%–48.34% versus 23.48%–28.25% for AgNPs. Furthermore, molecular docking analysis suggested a potential mechanism of action. Key phytoconstituents, stigmasterol and beta‐sitosterol glucoside, showed strong binding affinities to the CHIKV nsP2 protease. Stigmasterol exhibited the highest affinity (‐11.26 kcal/mol), while β‐sitosterol showed a binding energy of −9.55 kcal/mol, suggesting their potential role in disrupting viral replication through interactions with key amino acid residues of the active site. These findings suggest that A. paniculata extract possesses preliminary antiviral activity against CHIKV, as assessed by indirect MTT‐based cytotoxicity screening, and warrants further investigation using direct viral quantification approaches.