The biosynthesis of protoberberine and related isoquinoline alkaloids

Abstract

The biosynthesis of berberine and hydrastine (in Hydrastis canadensis), corydaline and protopine (in Corydalis solida), and ochotensimine and protopine (in C. ochotensis), has been investigated by the administration of [3-¹⁴C]-3′,4′-dihydroxyphenylalanine ([3-¹⁴C]DOPA). In all cases, incorporation of label was predominantly into the isoquinoline portion of the alkaloid. The role of DOPA in the early stages of isoquinoline alkaloid biosynthesis in these plants is discussed in the light of this and other relevant data. In addition, the later stages of corydaline biosynthesis have been studied by the administration of [9-methoxy-¹⁴C]palmatine and -tetrahydropalmatine to C. solida, and the origin of the exocyclic carbons of ochotensimine further verified by feeding [methyl-¹⁴C,³H]methionine to C. ochotensis.