Early Steps of Dauricine Biosynthesis in Cultured Roots of Menispermum dauricum

Abstract

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