Isoflavone glucosides (2'-hydroxy,5-methoxy genistein-7-O-glucoside (1), 2'-hydroxy genistein-7-O-gentibioside (2), 5-methoxy genistein-7-O-glucoside (3), 3',5-dimethoxy genistein-7-O-glucoside (4), 2'-hydroxy genistein-7-O-glucoside (5), genistein-7-O-gentibioside (6), 2'-hydroxy,5-methoxy genistein-4',7-O-diglucoside (7), and 2'-hydroxy genistein-4',7-O-diglucoside (8)) were isolated from the groundnut of Apios americana Medik. Their structures were elucidated on the basis of HR-ESI-MS and 1D- and 2D-NMR analyses. Compounds 1, 2, 4, and 7 are new compounds presented here for the first time. Compounds 2 and 5 were proven to be androgen receptor antagonists due to their binding activities for androgen receptors (IC50 280 and 160 μM, respectively) and the inhibitory activity of androgen-induced expression of prostate-specific antigen (PSA) mRNA in LNCaP (prostate adenocarcinoma) cells (IC50 20 and 18 μM, respectively).