Antiviral activity of a standardized root water extract of Eurycoma longifolia (Physta®) against dengue virus

The aim of this study was to investigate the antiviral property of Eurycoma longifolia Jack (EL) against dengue virus. A propriety standardized extract of Eurycoma longifolia Jack (Physta®) was tested for anti-viral activity after viral adsorption in Vero cell line. Viral yield was measured by qRT-PCR in four serotypes of dengue virus. The antiviral activity was further investigated in an in vivo AG129 mouse model for dengue inhibitory candidates. 100 mg/kg EL extract was fed twice daily and challenged with a lethal dose of (~1x10⁵ PFU per mouse) of DENV-2 over a period of six days. Antiviral activity with IC₅₀ of 33.84, 33.55, 58.35 and 119 µg/ml for DENV-1, DENV-2, DENV-3 and DENV-4 serotypes respectively was observed. The selectivity index (SI) values determined as the ratio of cytotoxic concentration (CC₅₀) to inhibitory concentration (IC₅₀) was the lowest for DENV-2 at 28.9. The dengue virus (DENV) replication measured by qRT-PCR showed a reduction of 100% for DENV-1, DENV-2, DENV-3 and 80% for DENV-4 at day 2 of exposure. In the in vivo AG129 mouse model, a lower weight reduction, 30% lower viral load and 12% higher platelet in the extract group compared to the control was observed at day 6. The extract of E. longifolia has potential anti-dengue properties with improving trends in platelet counts. E. longifolia supplementation is potentially a two-pronged approach in treating dengue fever.