OBJECTIVE Dengue virus belongs to the Flaviviridaefamily,and causes dengue fever and its related complications.Currently,there are no antiviral agents or licensed vaccines against dengue in humans.Houttuyniacordata Thunb.(Saururaceae)is documented to possess antiviral activity against several medically important viruses.METHODS The in vitro activities of the total ethyl acetate(EA)extracts of two batches of H.cordata,five EA fractions,and four of its constituent polyphenols(chlorogenic acid,hyperoside,quercetin,and quercitrin)against the new guinea C strain of dengue-2 virus were investigated.RESULTS Using the plaque reduction test,the total EA extracts of H.cordatainhibited viral infectivity when pre-incubated with virus before the viral adsorption stage,but exhibited no dose-dependent response when added to the cells at 6h post-infection.The 50% inhibitory concentration(IC50)of total EA extracts from two batches of H.cordata added before the viral adsorption stage were 0.24±3.1μg·mL-1 and 0.04±4.6μg·mL-1.However,only one out of five tested EA fractions showed considerably- weaker IC50 of 333μg·mL1.The pure polyphenol compounds displayed some anti-dengue activity,with their combinations yielding greater antiviral effects,especially the combination of chlorogenic acid and hyperoside with a high selectivity index.However,the enhanced efficacy of the polyphenol combinations was still less than that of the total EA extracts which revealed absence of cytotoxicity.Therefore,there may be other compounds in H.cordatathat contribute to the superior efficacy of the EA extracts.CONCLUSION We conclude that H.cordata possesses anti-dengue-2 virus activity,and harbors potential for the development of antiviral agents against dengue. OBJECTIVE Dengue virus belongs to the Flaviviridaefamily, and causes dengue fever and its related complications. Current there, there are no antiviral agents or licensed vaccines against dengue in humans. Houttuyniacordata Thunb. (Saururaceae) is documented to possess antiviral activity against several medically important viruses. METHODS The in vitro activities of the total ethyl acetate (EA) extracts of two batches of H. cordata, five EA fractions, and four of its constituent polyphenols (chlorogenic acid, hyperoside, quercetin, and quercitrin) against the new guinea C strain of The dengue-2 virus were investigated. RESULTS Using the plaque reduction test, the total EA extracts of H.cordatainhibited viral infectivity when pre-incubated with virus before the viral adsorption stage, but but no dose-dependent response when added to the cells at 6h post-infection. The 50% inhibitory concentration (IC50) of total EA extracts from two batches of H. cordata added before the viral adsorption stage were 0.24 ± 3.1 μg · mL-1 and 0.04 ± 4.6 μg · mL-1.However, only one out of five tested EA-fractions showed that the weaker IC50 of 333 μg · mL 1. The pure polyphenol compounds displayed some anti-dengue activity, with their combination yielding greater antiviral effects, especially the combination of chlorogenic acid and hyperoside with a high selectivity index. Still, the enhanced efficacy of the polyphenol combinations was still less than that of the total EA extracts that revealed absence of cytotoxicity. Wherefore there may be other compounds in H . cordatat contribute to the superior efficacy of the EA extracts. CONCLUSION We conclude that H.cordata possesses anti-dengue-2 virus activity, and harbors potential for the development of antiviral agents against dengue.