The possibility of the biomimetic transformation of (+)-matrine N-oxide, a main alkaloid in Sophora flavescens var. angustifolia, under various oxidative conditions was examined by the use of several metallic ions.When (+)-matrine N-oxide was warmed with FeSO4, or Fe(COOH)2 in MeOH-H2O at 40°C, (-)-7, 11-didehydromatrine [(-)-leontalbinine], a minor alkaloid in the same plant, was obtained along with (+)-matrine. This selective formation of (-)-leontalbinine seems to be specific to the reaction of (+)-matrine N-oxide with ferrous reagents.In addition, the structure of the newly isolated minor lupin alkaloid from the seeds of S. flavescens. was determined as (-)-leontalbinine N-oxide from its spectral comparison with the authentic sample.