Antiallergic principles from Alpinia galanga: structural requirements of phenylpropanoids for inhibition of degranulation and release of TNF-α and IL-4 in RBL-2H3 cells

The 80% aqueous acetone extract of the rhizomes of Alpinia galanga was found to inhibit release of β-hexosaminidase, as a marker of antigen-IgE-mediated degranulation in RBL-2H3 cells. Nine known phenylpropanoids and p-hydroxybenzaldehyde were isolated from the extract. Among them, 1′S-1′-acetoxychavicol acetate and 1′S-1′-acetoxyeugenol acetate exhibited potent inhibitory activity with IC50 values of 15 and 19 μM. From the effects of various related compounds, both the 1′- and 4-acetoxyl groups of 1′S-1′-acetoxychavicol acetate and 1′S-1′-acetoxyeugenol acetate were essential for their strong activity, and the 2′–3′ double bond enhanced the activity. In addition, 1′S-1′-acetoxychavicol acetate and 1′S-1′-acetoxyeugenol acetate inhibited ear passive cutaneous anaphylaxis reactions in mice and the antigen-IgE-mediated TNF-α and IL-4 production, both of which participate in the late phase of type I allergic reactions, in RBL-2H3 cells.