Ishizuchi dark tea suppresses IgE-mediated degranulation of RBL-2H3 cells and nasal rubbing behavior of pollinosis in mice

Ishizuchi dark tea is a microorganism-fermented tea produced in Ehime, Japan. We herein describe the anti-allergic effect of Ishizuchi dark tea. The water extract from Ishizuchi dark tea suppressed degranulation of RBL-2H3 cells in a dose-dependent manner with no apparent cytotoxicity. Fractionation and β-hexosaminidase release assay of the tea components revealed theabrownins as the major bioactive substance in Ishizuchi dark tea. Phosphorylation of Syk, a tyrosine kinase, tended to be suppressed by treating RBL-2H3 cells with theabrownins. In addition, Ishizuchi dark tea suppressed an allergic symptom in the Cry j1-induced pollinosis model mice. Taken together, these data indicated that Ishizuchi dark tea would be a beneficial functional food with an anti-allergic effect.