Chalcones as novel influenza A (H1N1) neuraminidase inhibitors from Glycyrrhiza inflata

One new licochalcone G (1) and seven known (2-8) chalcones were isolated as inhibitory principles on influenza A virus from the acetone extract of Glycyrrhiza inflata. Compounds 3 and 6 without prenyl group showed strong inhibitory effects on various neuraminidases from influenza viral strains, H1N1 and H9N2, and more novel H1N1 (WT) and oseltamivir-resistant novel H1N1 (H274Y) expressed in 293T cells. In addition, the efficacy of oseltamivir with the presence of compound 3 (5 μM) was increased against H274Y neuraminidase.