Antiviral effect in vitro of extract from seed of Litchi chinensis Sonn and preliminary study on its antiviral mode

Aim:To study the antiviral effect of extract from seed of Litchi chinensis Sonn(LSE) in vitro,and to detect its antiviral mode.Methods:Both the cytopathic effect(CPE) reduction assay and MTT assay were used to detect the antiviral activity of LSE on Coxsackie virus B3(Cox B3),respiratory syncytial virus(RSV) long strain and herpes simplex virus type 1 and type 2(HSV-1 and HSV-2) standard strain.The mode of LSE anti-HSV effect was studied by direct virucidal assay,pre-treatment assay,inhibition of viral attachment assay and time of addition assay.Results:It was shown that the LSE had moderate cytotoxicity on these three host cells,i.e.HeLa,HEp-2 and Vero cells.It had no inhibition on Cox B3 in HeLa cells,but showed potent antiviral action on RSV long strain,HSV-1 and HSV-2 standard strain in concentration dependent manner.IC50 determinations on these three viruses were 32.3,27.9 and 20.4 μg/mL,respectively.In addition,Vero cells,which was pre-incubated with LSE,were infected with HSV-1.LSE had direct virucidal activity.Furthermore,it inhibited the attachment of HSV-1 on Vero cells and the inhibitory ratio was about 51% at the concentration of 31.3 μg/mL.Finally,it was found in time of addition assay that the LSE did inhibit the replication of HSV-1 in Vero cells thereby showing a high anti-HSV effect.Conclusion:Litchi seed extract possesses noticeable anti RSV and HSV effects,and the mode of anti-HSV is multiplicity.