Biological activity of new flavonoids and phenolic compounds from Cirsium italicum (Savi) DC.

Cirsium italicum (Savi) DC. was researched for its phytochemicals for the first time. Two new biflavonoids, 5,5'',7''-trihydroxy-3,7-dimethoxy-4'-4'''-O-biflavone (3), (8,3',4',5'-tetrahydroxy-7-O-alpha-glucosyl isoflavone)-6-8''-(4'''-hydroxy-7''-O-alpha-glucosyl isoflavone) biflavone (7), a new isoflavone, 6-2'-dihydroxy-5-methoxy isoflavonone-4'-O-alpha-D-glucopyranoside (5) and a new phenolic compound, ethyl-(2,3-dihydroxy-5,6-dimethoxy-4-acetyl) benzoate (4), together with three known compounds (1), (2) and (6) were isolated from Cirsium italicum. Their structures were elucidated by extensive 1D and 2D NMR, and MS data analyses. All compounds isolated from C. italicum exhibited antioxidant activity. However, the highest activity of the EtOAc extract is considered to be responsible for compounds (1), (2) and (3) being the main compounds.