Absolute stereostructures of three new sesquiterpenes from the fruit of Alpinia oxyphylla with inhibitory effects on nitric oxide production and degranulation in RBL-2H3 cells

The 80% aqueous acetone extract and the ethyl acetate-soluble portion from the dried fruit of Alpinia oxyphylla MIQUEL were found to show inhibitory effects on nitric oxide production in lipopolysaccharide-activated macrophages and antigen-induced degranulation in RBL-2H3 cells. A new eudesmane-type sesquiterpene, oxyphyllol A, and two eremophilane-type sesquiterpenes, oxyphyllols B and C, were isolated from the ethyl acetate-soluble portion, together with 16 known constituents. The absolute stereostructures of oxyphyllols A, B, and C were determined on the basis of chemical and physicochemical evidence. The effects of isolated components on nitric oxide production were examined, and nine constituents including oxyphyllol A and nootkatone were found to show inhibitory activity. On the other hand, five constituents inhibited the release of beta-hexosaminidase from RBL-2H3 cells.