Structure Elucidation of New Kavalactone Dimers From Alpinia zerumbet Pericarps Using NMR Calculations

Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm, known as shell ginger, is an aromatic plant widely distributed in tropical and subtropical regions. In Guizhou Province of China, its mature fruits have been used by the Miao people for the treatment of cardiovascular diseases. Although the bioactivities of mature fruits of A. zerumbet are derived from phytochemicals in the seeds and pericarps of the plant, there remains a dearth of reports on the isolation of phytochemicals from the pericarp of A. zerumbet. In the present study, the pericarps of mature fruits of A. zerumbet were extracted, and two new kavalactone dimers, alpingsin E (1) and aniba dimer D (2), were isolated. Their structures were determined on the basis of extensive spectroscopic analysis and NMR calculations. Especially, density functional theory–based NMR chemical shift calculations were employed to elucidate and confirm the relative configuration of 1 and 2.