Figure 1.

Inhibitory effects of S. cusia leaf methanol extract on viral cytopathicity and progeny virus production in HCoV-NL63-infected cells. LLC-MK-2 cells were infected with HCoV-NL63 at 0.01 multiplicity of infection (MOI) and simultaneously treated with the extract. Virus-induced cytopathic effects were imaged 36 h post-infection (hpi) by microscopy (A). The supernatant from treated infected cells was harvested 36 hpi and serially diluted for determining the HCoV-NL63 yield in the supernatant using the plaque assay (B, right y axis). The rate of virus yield inhibition was calculated based on the ratio of the loss in the titer of the treated group to mock-treated group (B, left y axis). +, add; −, not add; *, p value < 0.05; ***, p value < 0.001 compared with mock-treated infected cells. Scale bar, 100 μM.