Early Steps of Dauricine Biosynthesis in Cultured Roots of Menispermum dauricum.

Cultured roots of Menispermum dauricum, a rich source of the bisbenzylisoquinoline alkaloid dauricine (1), were fed with L-[U-C-14] tyrosine, L-[3-C-13] tyrosine, and [2-C-13] tyramine independently, and the incorporation of possible early precursors into 1 was studied. The results demonstrated that 1 was composed of four molecules of tyrosine, and that tyramine was specifically incorporated into the isoquinoline portions of 1. The unusual chlorine-containing alkaloid acutumine (3), into which C-14-labeled tyrosine was also incorporated, was identified as one of the main constituents in the alkaloid fraction from the roots.