Suppressive Effect of <i> Chrysanthemum <b>×</b> Morifolium </i> Ramat. on Type I Hypersensitivity Reactions and Its Molecular Mechanism

<i>Chrysanthemum × morifolium</i> Ramat. (CM) has long been valued as both an ornamental plant and also for its medicinal and culinary uses. In Japanese folk medicine, a decoction of CM capitulum (CMC) is taken to relieve hay fever symptoms. Previous studies have confirmed the anti-type I hypersensitivity activity of CMC, although its mechanism of action remains unclear. This study reports that two dried CMC extracts-Hachinohegiku capitulum extracts (HCE) and Abokew capitulum extracts (ACE)-among three edible CM cultivars tested, significantly inhibited passive cutaneous anaphylaxis (PCA), an <i>in vivo</i> model of type I hypersensitivity. In mast cell model RBL-2H3 cells, all three extracts, HCE, ACE, and Enmeiraku capitulum extracts (ECE) suppressed antigen-antibody-induced increases in intracellular Ca²⁺ concentration and degranulation in a concentration-dependent manner. The strength of inhibition correlated with the degree of PCA suppression. Activation of PLCγ1, a key protein in the antigen-antibody signaling cascade, was significantly inhibited only by ACE, which showed the strongest PCA inhibition. Both HCE and ACE significantly reduced Akt activation, whereas ECE, which lacked significant PCA activity, did not inhibit either protein. The degree of protein-activation inhibition corresponded with suppression of Ca²⁺ elevation, degranulation, and PCA response. These findings suggest that inhibition of PLCγ1 and Akt activation underlies the anti-type I hypersensitivity effects of HCE and ACE.