Phlorotannin is the collective term for polyphenols derived from brown algae 
belonging to the genera Ascopyllum, Ecklonia, Eisenia, Fucus and Sargassum etc. 
Since the incidence of allergies is currently increasing in the world, there is 
a focus on phlorotannins having anti-allergic and anti-inflammatory effects. In 
this study, six purified phlorotannins (eckol; 6,6'-bieckol; 6,8'-bieckol; 
8,8'-bieckol; phlorofucofuroeckol (PFF)-A and PFF-B) from Eisenia arborea, 
orally administered to mice, were examined for their suppression effects on ear 
swelling. In considering the suppression, we also examined whether the 
phlorotannins suppressed release of chemical mediators (histamine, leukotriene 
B₄ and prostaglandin E₂), and mRNA expression and/or the activity of 
cyclooxygenase-2 (COX-2), using RBL-2H3 cells, a cultured mast cell model. 
Results showed that the phlorotnannins exhibited suppression effects in all 
experiments, with 6,8'-bieckol, 8,8'-bieckol and PFF-A showing the strongest of 
these effects. In conclusion, orally administered phlorotannins suppress mouse 
ear swelling, and this mechanism apparently involves suppression of chemical 
mediator release and COX-2 mRNA expression or activity. This is the first report 
of the anti-allergic effects of the orally administered purified phlorotannins 
in vivo. Phlorotannins show potential for use in functional foods or drugs.