RESUMO
Objective: To evaluate the in vitro activities of the ethyl acetate (EA) fraction of Houttuynia cordata (H. cordata) Thunb. (Saururaceae) and three of its constituent flavonoids (quercetin, quercitrin and rutin) against murine coronavirus and dengue virus (DENV). Methods: The antiviral activities of various concentrations of the EA fraction of H. cordata and flavonoids were assessed using virus neutralization tests against mouse hepatitis virus (MHV) and DENV type 2 (DENV-2). Cinanserin hydrochloride was also tested against MHV. The EA fraction of H. cordata was tested for acute oral toxicity in C57BL/6 mice. Results: The EA fraction of H. cordata inhibited viral infectivity up to 6 d. Cinanserin hydrochloride was able to inhibit MHV for only 2 d. The 50% inhibitory concentrations (IC