Two novel monoterpene–chalcone conjugates isolated from the seeds of Alpinia katsumadai

Three monoterpene–chalcone conjugates, including two novel compounds isorubraine (2) and sumadain C (3), and a known compound rubraine (1) were isolated from the seeds of Alpinia katsumadai. Their structures and relative configurations were established by NMR spectroscopy and X-ray crystallography. Cytotoxic activities of these compounds were evaluated against cell lines HepG2, MCF-7 and MAD-MB-435, and compound 3 exhibited potent cytotoxic...