Fig. 2.

Neutral PCA shows antiviral activity against PR8 virus. a–c PR8 virus was mixed with equal volume of PBS, PCA (a), ferulic acid (b), hibiscus acid, or hibiscus acid-Na (c). Acidic (non-pH-adjusted) PCA, ferulic acid, and hibiscus acid, and neutral (pH-adjusted) solutions of these compounds were prepared. Acidic PBS was also prepared. An estimated pH of the mixture was determined using pH measurement of a virus-free mixture as a substitute for a virus-containing mixture. The pH shown was an approximate value with a range ± 0.3. The mixture was placed at 26 °C for 10 min or 48 h and was inoculated into MDCK cells. After a 3-day incubation, the viral titer of the mixture was evaluated using CPE observation. Error bars indicate mean ± SD; n = 3 per group. (a–c) Student’s t test (a, b), and Student’s t test with Bonferroni’s test (c) were performed to analyze statistical significance; **p < 0.01. The results represent more than three independent experiments