By using a cell-based high throughput screening campaign, a novel angelicin derivative 6a was identified to inhibit influenza A (H1N1) virus induced cytopathic effect in Madin− Darby canine kidney cell culture in low micromolar range. Detailed structure− activity relationship studies of 6a revealed that the angelicin scaffold is essential for activity in pharmacophore B, while meta-substituted phenyl/2-thiophene rings are optimal in pharmacophore A and C. ...