Significant differences in direct comparisons were determined using a Tukey’s post hoc test. Differences with p < 0.05, p < 0.01, and p < 0.001 were considered statistically significant. The antiviral Epacadostat activities of ginsenosides against CVB3 were assessed using the SRB method, which monitors the alteration

of CPE induced by virus infection. As a positive control, ribavirin, a commonly used antiviral drug, was included. Of the seven ginsenosides tested, ginsenosides Re, Rf, and Rg2, which are classified as PT-type ginsenosides, significantly inhibited CVB3-induced CPE, and increased the cell viability of Vero cells (Fig. 1). CVB3 infection induced approximately 60% cell death in Vero cells (40% of cell viability), and the treatment of cells with 100 μg/mL of Re, Rf, and Rg2 increased the cell viability to 75%, 60%, and 50%, respectively. Furthermore, 10 μg/mL of ginsenosides Re and Rg2 also significantly reduced the CPE EPZ5676 of CVB3 infection in Vero cells, albeit a weaker protective effect than that of ribavirin at the same concentration. By contrast, the PD-type ginsenosides Rb1, Rb2, Rc, and Rd did not exhibit any antiviral activity against CVB3, and 100 μg/mL of Rd, Rc, and Rb2 even significantly increased CVB3 infection-induced cytotoxicity (Fig. 1). In Vero cells treated with ribavirin after CVB3 infection, the drug exhibited significant

antiviral activity at 100 μg/mL and 10 μg/mL (Fig. 1), and the maximal efficacy of ribavirin was comparable to those of PT-type ginsenosides.

Ribavirin itself was slightly toxic to Vero cells Demeclocycline (cell viability of approximately 81% at 100 μg/mL), whereas none of the seven ginsenosides alone was toxic to Vero cells at the same concentration (Table 1). Collectively, these results suggest that ginsenosides Re, Rf, and Rg2 have significant antiviral activity against CVB3 without inducing cytotoxicity in Vero cells. Together with coxsackievirus A16, EV71 is one of the two major causative agents of hand, foot, and mouth disease, and thus we sought to investigate whether ginsenosides have antiviral activity against EV71 infection in Vero cells. Most ginsenosides assessed using the SRB method did not have significant antiviral activity against EV71, and only ginsenoside Rg slightly inhibited EV71 infection-induced cytotoxicity (Fig. 2). Infection with EV71 induced substantial cell death in Vero cells, resulting in approximately 25% cell viability. The antiviral effect of Rg2 (10 μg/mL and 100 μg/mL) in EV71-infected cells improved cell viability by 40%. The antiviral effect of Rg2 was shown to be dose-dependent, and the maximal antiviral efficacy of the compound is comparable to that of ribavirin. By contrast, other ginsenosides tested did not have significant antiviral activity against EV71 infection (Fig. 2).