Fig. 1.

a The structure of PPa. 1b Assay examining the ability of PPa to reduce the number of plaques of the influenza A/Puerto Rico/8/34 (H1N1) virus. The assay was performed using the “Pretreatment of the virus” and “During infection” approaches. In the first approach, 5 μg/mL PPa was pre-incubated with 100 TCID₅₀ of the virus for 30 min at 37 °C before being added into the cells, while in the latter approach, the same titer of virus mixed with PPa (5 μg/mL) was simultaneously added to cells. After an incubation at 37 °C in a 5% CO₂ atmosphere for 48 h, the cells were fixed and stained. 1c The number of plaques from each group were counted, and the plaque inhibition rate of PPa against the influenza A/Puerto Rico/8/34 (H1N1) virus was calculated.