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

Abstract

Phlorofucofuroeckol A (1), a novel phlorotannin with both dibenzo-1,4-dioxin and dibenzofuran elements, has been isolated from the brown alga Ecklonia kuroma 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 = 1.0 .mu.g/ml) an .alpha.2-plasmin inhibitor (IC50 = 0.3 .mu.g/ml), the main plasmin inhibitors in plasma.