A new base, dehydronantenine, was isolated from the tree bark of Nandina domestica THUNB., and its structure was formulated as (I) from ultraviolet and nuclear magnetic resonance spectra, especially by the application of nuclear Overhauser effect. I was synthesized by the dehydrogenation reaction of O-methyldomesticine (II) and its structure was proved. One kind of a neutral substance was also isolated and it was confirmed to be (-)-episyringaresinol (III).