A new biflavonoid, named asteryomenin (1), as well as six known phenolic compounds, esculetin (2), 4-O-${eta}$-D-glucopyranoside-3-hydroxy methyl benzoate (3), caffeic acid (4), isoquercitrin (5), isorhamnetin-3-O-glucoside (6), and apigenin (7) were isolated from the aerial parts of Aster yomena. The structures of compounds (1-7) were identified based on 1D and 2D NMR, including $^1H-^1H$ COSY, HSQC, HMBC and NOESY spectroscopic analyses. Compounds 2-7 were isolated from this plant for the first time. For these isolates, the inhibitory activity of IL-6 production in the $TNF-{alpha}$ stimulated MG-63 cell was examined. Among these isolates, compounds 4 and 7 appeared to have potent inhibitory activity of IL-6 production in the TNF-${alpha}$ stimulated MG-63 cell, while compounds 1-3 and 5-6 showed moderate activity.