To study the influence of antioxidants on PEDV replication, the antioxidants, NAC, trolox and PDTC were used. As shown in Figure 4A and 4B, the four compounds did not exhibit cytotoxicity at different concentrations. Antiviral activity of NAC and PDTC was hardly present. However, trolox strongly exhibited antiviral activity at 100 μg/ ml concentration, but decreased rapidly according to a dose dependent manner compared with Q7R.