Two Japanese pepper (Zanthoxylum piperitum) fruit-derived compounds attenuate IgE-mediated allergic response in vitro and in vivo via inhibition of mast cell degranulation

Zanthoxylum piperitum (ZP, 'Japanese pepper') is a traditional medicine and pepper used in Asian countries such as Japan. Hydroxy-α-sanshool, a pungent-tasting substance contained within ZP, has been reported to slightly suppress immunoglobulin E (IgE)-mediated mast cell degranulation. The current study aims to newly identify anti-allergic compounds derived from ZP. We examine the inhibitory mechanisms behind IgE-mediated mast cell degranulation. By inhibitory effect-guided isolation, we identified degranulation inhibitory compounds derived from ZP fruit: 1-acetoxy-7-hydroxy-3, 7-dimethylocta-2E, 5E-diene (ZP1) and 8-hydroxygeranyl acetate (ZP2). ZP1 and ZP2 inhibited IgE-mediated degranulation and A23187-mediated degranulation in RBL-2H3 mast cells. Our findings suggest the inhibition of degranulation by ZP1 and ZP2 was by inhibition of Lyn phosphorylation, followed by inhibition of intracellular Ca2+ mobilization, protein kinase C alpha phosphorylation, membrane ruffling, and granule-to-plasma membrane fusion. Oral administration of ZP1 or ZP2 attenuated an IgE-mediated passive cutaneous anaphylactic reaction in mice. Histological observation suggests that this effect occurred via inhibition of mast cell degranulation. These findings indicate that ZP1 and ZP2 attenuate allergic reaction via inhibition of IgE-mediated mast cell degranulation.