Fig. 1.

Hibiscus tea components show both acid-dependent antiviral activity and low-pH-independent antiviral activity against PR8 virus. a PR8 virus was mixed with an equal volume of PBS or Hib[crude]. The pH of PBS and Hib[crude] was adjusted from acidic to approximately neutral. The pH shown was an approximate value with a range ± 0.3. The mixture which was placed at 26 °C for 10 min or 24 h and inoculated in MDCK cells. After a 3-day incubation, the viral titer of the mixture was evaluated using CPE observation. b The mixture containing acidic and neutral PBS, Hib[crude], or frHibis was placed at 26 °C for 10 min or 48 h. The mixture was inoculated to MDCK cells. After a 3-day incubation, the viral titer of the mixture was evaluated. Error bars indicate mean ± SD; n = 3 per group. (a, b) Student’s t test (a), and Student’s t test with Bonferroni’s test (b) were performed to analyze statistical significance; *p < 0.05, **p < 0.01. The results represent three independent experiments