Flavonoids from Iris songarica and their Antioxidant and Estrogenic Activity

A new dihydroflavonol, songaricol (1) and seven known flavonoids, ayamenin A (2), irisflavone A (3), 5,7-dihydroxy-2',6-dimethoxyisoflavone (4), irilin B (5), 5,3'-dihydroxy-7,8,2'-trimethoxyisoflavone (6) and irisoid A (7) were isolated from rhizome and roots of Iris songarica. Structure elucidation of 1 was achieved through extensive NMR and circular dichroism techniques. Compounds 1, 5 and 7 showed antioxidant activity in HL-60 cells (IC50 values of 21, 11 and 3.8 mu g/mL), whereas 2, 5 and the previously isolated irisone B were able to show estrogenic response (EC50 values of 305.5, 159.7 and 322.0 mu g/mL) in yeast cells expressing human estrogen receptor (ER-alpha).