Antioxidant α-amylase inhibitors flavonoids from Iris germanica rhizomes

A new isoflavonoid glycoside, iridin A (9), along with eight known isoflavonoids: irilone 4′ -methyl ether (1), irilone (2), irisolidone (3), irigenin S (4), irigenin (5), irilone 4′ -O-β-d-glucopyranoside (6), iridin S (7), and iridin (8) were separated from Iris × germanica L., Iridaceae, rhizomes. The structural elucidation of these flavonoids was achieved with the aid of extensive spectroscopic techniques and comparing with the published data. They were estimated for their α-amylase and 1,1-diphenyl-2-picrylhydrazyl inhibitory capacities. Compounds 3, 5, and 9 showed α-amylase inhibitory activities with % inhibition 70.8, 67.5, and 70.5, respectively compared to acarbose (a reference α-amylase inhibitor). Moreover, 9 exhibited moderate antioxidant activity with IC50 8.91 μM.