that potently inhibited SGLT1 and SGLT2. These flavonoids more potently inhibited SGLT2 than SGLT1. Furthermore, SGLT1-inhibitory flavanones ((-)-Kurarinone, Kushenol N, Sophoraflavanone G) and the chalcone of (-)-Kurarinone share a common functional group in their structures, the lavandulyl group of C-8 or C-5 (chalcone). These results suggest that the lavandulyl group in the flavanone skeleton plays a crucial role in SGLT1-inhibitory activity. In addition, SGLT2-inhibitory isoflavonoids require a hydroxyl group in their structures, and lavandulyl flavanones require a dehydroxy group of C-3. Furthermore, the methoxy group in the flavanone skeleton of C-5 may augment inhibitory activities against SGLTs.