Anti-plasmin inhibitor. VI. Structure of phlorofucofuroeckol A, a novel phlorotannin with both dibenzo-1,4-dioxin and dibenzofuran elements, from Ecklonia kurome Okamura.

Phlorofucofuroeckol A (1), a novel phlorotannin with both dibenzo-1,4-dioxin and dibenzofuran elements, has been isolated from the brown alga Ecklonia kurome OKAMURA as a potent anti-plasmin inhibitor. Its structure has been elucidated to be 1,11-di(3,5-dihydroxyphenoxy)- benzofuro[3,2-a]dibenzo[b,e][1,4]dioxin-2,4,8,10,14-pentaol on the basis of the spectral data, in particular, by means of negative nuclear Overhauser effect (NOE) and long-range carbon-proton couplings (2JCH and 3JCH). Phlorofucofuroeckol A inhibited the action of alpha 2-macroglobulin (IC50 = 1.

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 (alpha 2-macroglobulin and alpha 2-plasmin inhibitor) and some proteases have been examined.

Structure of an anti-plasmin inhibitor, eckol, isolated from the brown alga Ecklonia kurome Okamura and inhibitory activities of its derivatives on plasma plasmin inhibitors.

Eckol (1), a novel phlorotannin with a dibenzo-1,4-dioxin skeleton, has been isolated from the brown alga Ecklonia kurome Okamura as a potent and specific anti-plasmin inhibitor. Its structure has been elucidated based on the spectral data, in particular, by means of negative nuclear Overhauser effect (NOE), and finally established as 1-(3,5-dihydroxyphenoxy)-2,4,7,9-tetrahydroxydibenzo-1,4-dio xin by X-ray analysis. Some partially methoxylated derivatives of eckol were prepared by methylation with diazomethane and also by selective dimethylation of eckol permethylate (1b) to establish the structural requirements for inhibitory activities on alpha 2-macroglobulin and alpha 2-plasmin inhibitor, the main plasmin inhibitors in plasma.