THE ROLE OF β-ALANINE AND OF GLYCERATE IN THE BIOSYNTHESIS OF RICININE

Abstract

β-Alanine-2-14C has been fed to young Ricinuscommunis L. plants and the radioactive ricinine isolated. The activity of each carbon in the alkaloid molecule was determined. Propionate-2-14C was also fed to young Ricinus plants and the radioactivity on carbons 2 and 3 of the isolated ricinine was determined. The pattern of labelling produced by β-alanine-2-14C was very similar to that produced by propionate-2-14C, but was quite distinct from that produced when succinate-2,3-14C or acetate-2-14C was fed to the plant. Whereas with the latter, carbons 2 and 3 of the pyridone ring of ricinine are approximately equally labelled, the ricinine obtained after propionate-2-14C or β-alanine-2-14C was fed contains on carbon 3 almost twice the activity contained on carbon 2.It has been found that acetate-2-14C is not incorporated into carbon 6 of ricinine. It has also been established that (±)-glycerate-1-14C is incorporated into ricinine only negligibly (0.12%), whereas labelled glycerol is incorporated to the extent of 2.7–3.9%. Glycerate-3-14C, however, is known to be incorporated into the pyridine ring of nicotine; therefore, glyceric acid must undergo decarboxylation before incorporation.