Three novel sesquiterpene peroxides, hanalpinol peroxide (I), isohanalpinol (II), and aokumanol (III), a new secoguaiane-type sesquiterpene, epialpinolide (IV), and a new elemophilane-type sesquiterpene, Δ^{11 (12)} -eremophilen-10β-ol (V), have been isolated from the rhizomes of Alpinia intermedia together with eight known sesquiterpenes, hanalpinol (VI), hanalpinone (VII), isohanalpinone (VIII), alpinenone (IX), furopelargone B (X), furopelargone A (XI), intermedeol (XII) and β-selinene (XIII). The structures of I-V were determined by spectroscopic methods, chemical conversion, and X-ray analysis. Their biosynthetic relationships are discussed.
From the point of view of chemotaxonomy, it is suggested that Alpinia intermedia and Alpinia japonica are closely related plants.