Yatein is a natural product isolated from from Cleistanthus boivinianu or Chamaecyparis obtusa. Yatein suppresses herpes simplex virus type 1 replication in HeLa cells by interruption the immediate-early gene expression. The mechanisms of antiviral action of yatein seem to be mediated, by inhibiting HSV-1 α gene expression, including expression of the ICP0 and ICP4 genes, and by arresting HSV-1 DNA synthesis and structural protein expression in HeLa cells. Yatein showed antiproliferative activity against the HCT-116 human colon carcinoma cell line, with an IC50 > 10 uM.