Time-of-addition effect on HRV-4 replication in HeLa cells. Approximately twofold quantities of the IC50 values of ellagic acid (EA) and ribavirin (RN) were applied. The 50 μg/mL EA and 100 μg/mL RN were added at various times preinfection (-1 h), coinfection (0 h), or postinfection (1, 2, 4, and 6 h) of human rhinovirus-4 (HRV-4) to HeLa cells at 37°C. After 2 days, inhibition was evaluated by SRB method and expressed as the inhibition rate. Each bar represents the mean ± SD of triplicate samples of three independent experiments.