Magnolol and honokiol: inhibitors against mouse passive cutaneous anaphylaxis reaction and scratching behaviors.

The antiallergic effects of magnolol and honokiol, isolated from the bark of Magnolia obovata (family Magnoliaceae), were investigated both in vitro and in vivo. Magnolol and honokiol potently inhibited passive cutaneous anaphylaxis reactions in mice induced by IgE-antigen complex as well as compound 48/80-induced scratching behaviors. These constituents exhibited not only potent inhibitory activity on the degranulation of RBL-2H3 cells induced by IgE-antigen complex, with IC 50 values of 45 and 55 μM, respectively, but also inhibited the protein expressions of IL-4 and TNF-a. Based on these findings, magnolol and honokiol may improve IgE-induced allergic diseases.