Inhibitory activity of brown algal phlorotannins against hyaluronidase

Abstract The inhibitory effect of brown algal phlorotannins on hyaluronidase was evaluated by an in vitro assay. Crude phlorotannins from the brown algae Eisenia bicyclis and Ecklonia kurome had a stronger inhibitory effect than well-known inhibitors such as catechins and sodium cromoglycate. IC50 values of the following six phlorotannins: phloroglucinol, an unknown tetramer, eckol (a trimer), phlorofucofuroeckol A (a pentamer), dieckol and 8,8′-bieckol (hexamers), were 280, 650, >800, 140, 120 and 40 μm, respectively. The IC50 of catechin, epigallocatechin gallate and sodium cromoglycate was 620, 190 and 270 μm, respectively. 8,8′-Bieckol, the strongest HAase inhibitor in this study, acted as a competitive inhibitor with an inhibition constant (Ki) of 35 μm. Acetylation of the phlorotannins markedly decreased their inhibitory potency.