Cytotoxicity and antiviral activity of 3b. (A) Chemical structure of compound 3b. (B) Vero cells were incubated for 96 h in the presence of different concentrations of 3b and then cell viability was determined by MTT assay (■). Other set of cultures were infected with DENV-2 (MOI 0.1 PFU/cell) in the presence or absence of 3b and virus yields were determined at 48 h p.i. (□). (C) Effect of 3b on cell protein synthesis. Vero cells were incubated for 48 h with or without 100 μM 3b. Then, cells were labeled with 100 μCi/ml EXPRE35S-35S for 4 h and polypeptides were electrophoresed. (D) Vero cells were infected with DENV-1 (■), DENV-3(▲) or DENV-4 (∆) at a MOI of 0.1 PFU/cell in the presence or absence of 3b and virus yields were determined at 48 h p.i. (E) Cytotoxicity (■) and antiviral activity (□) against DENV-2 (MOI 0.1 PFU/cell) were determined in HeLa cells as in (B). In (B), (D) and (E) results are expressed as % cell viability or virus yield with respect to control without drug treatment and represent the mean of three independent experiments ± standard deviation.