Excoecarianin, Isolated from Phyllanthus urinaria Linnea, Inhibits Herpes Simplex Virus Type 2 Infection through Inactivation of Viral Particles

Phyllanthus urinaria Linnea (Euphorbiaceae) is one of the traditional medicinal plants widely used by oriental people to treat various diseases. We have previously demonstrated that the acetone extract of P. urinaria inhibits herpes simplex virus type 2 (HSV-2) but not HSV-1 infection. In a continuing effort to clarify the antiviral mechanisms of P. urinaria, we isolated the pure compound excoecarianin from the whole plant of P. urinaria through acetone extraction, and investigated its anti-HSV-1 and HSV-2 activities. Our results indicated that excoecarianin protected Vero cells from HSV-2 but not HSV-1 infection, and its 50% inhibitory concentration (IC50) was 1.4 ± 0.1 μM. The antiviral effective concentration of excoecarianin did not affect the viability or the morphology of Vero cells. Although excoecarianin inhibited HSV-2 infection, the inhibitory effect, however, was most prominent when excoecarianin was concurrently added with the virus. Pretreatment of Vero cells with excoecarianin with removal of the drug prior to infection did not yield any antiviral effects, and the same observation was made for post viral entry treatment. Subsequent studies revealed that excoecarianin inactivated HSV-2 virus particles to prevent viral infection. A synergistic antiviral effect against HSV-2 was also observed when Vero cells were treated with a combination of acyclovir (ACV) and excoecarianin. These results suggested that excoecarianin merits to be further explored as an entry inhibitor against HSV-2 and could potentially be investigated for combinatorial drug treatment with nucleoside analogues such as ACV in therapeutic management of HSV-2 infection

Artemisia capillaris inhibited enterovirus 71-induced cell injury by preventing viral internalization

Artemisia capillaris (A. capillaris) is a common herbal drug used for thousands years in ancient China. A. capillaris has been empirically used to manage hand-foot-mouth disease (HFMD), which is commonly caused by enterovirus 71 (EV71). EV71 can cause meningoencephalitis with mortality and neurologic sequelae without effective management. It is presently unknown whether A. capillaris is effective against EV71 infection. To test the hypothesis that it could protect cells from EV71-induced injury, a hot water extract of A. capillaris was tested in human foreskin fibroblast cells (CCFS-1/KMC) and human rhabdomyosarcoma cells (RD cells) by plaque reduction assay and flow cytometry. Inhibition of viral replication was examined by reverse quantitative RT-PCR (qRT-PCR). Its effect on translations of viral proteins (VP0, VP1, VP2, protease 2B and 3AB), and apoptotic proteins were examined by western blot. A. capillaris was dose-dependently effective against EV71 infection in both CCFS-1/KMC cells and RD cells by inhibiting viral internalization. However, A. capillaris was minimally effective on viral attachment, VP2 translation, and inhibition of virus-induced apoptosis. Further isolation of effective molecules is needed. In conclusion, A. capillaris has anti-EV71 activity mainly by inhibiting viral internalization. A. capillaris would be better to manage EV71 infection in combination with other agents