Figure 2.

Antiviral activities of diphyllin 1 and cleistanthin B 8. (A,C–F) Anti-antiviral activities of diphyllin 1. Vero cell monolayers were treated with diphyllin 1 (0 to 25 µM) either 2 h prior to TBEV (A), ZIKV (C), WNV (D), RVFV (E), and HSV-1 (F) infection (at a MOI of 0.1) (2 h pre-treatment), simultaneously with virus infection (simultaneous treatment), or 2 h after infection (2 h post-treatment). The infected cells were then incubated for 48 h, after which cell media were collected, and viral titers were determined using a plaque assay and expressed as PFU/mL. (B) Anti-TBEV activity of cleistanthin B 8 (0 to 25 µM). The experimental procedure was the same as in (A). (G) Anti-RABV activity of diphyllin 1. A suspension of BHK-21 cells was incubated with diphyllin 1 (0 to 25 µM) and with RABV (10^6.58 TCID₅₀/mL) at 37 °C for 40 mins. Following incubation, the RABV-infected cells were seeded on 96 well plates and cultivated for 72 h then, media were collected, and the RABV RNA was quantified by RT-qPCR. (H) Inhibition curves for diphyllin 1 were constructed from the viral titer values (2 h pre-treatment) in order to estimate EC₅₀ values for the indicated viruses. The mean titers from three biological replicates of two independent experiments are shown, and error bars indicate standard errors of the mean (n = 3). The horizontal dashed line indicates the minimum detectable threshold of 1.44 log₁₀ PFU/mL. MI, MacIntyre.