Anti-plasmin Inhibitor. V. : Structures of Novel Dimeric Eckols Isolated from the Brown Alga Ecklonia kurome OKAMURA

6, 6'-Bieckol (1), 2-O-(2, 4, 6-trihydroxyphenyl)-6, 6'-bieckol (4), and 8, 8'-bieckol (2), bispolyphenols with a dibenzo-1, 4-dioxin skeleton, have been isolated as potent anti-plasmin inhibitors from the brown alga Ecklonia kurome OKAMURA. Their structures have been determined to be dimers of eckol linked at the C-6 or C-8 positions, through an aryl-aryl bond on the basis of spectral data. Their inhibitory actions on anti-plasmins (α2-macroglobulin and α2-plasmin inhibitor) and some proteases have been examined.