A modified procedure for the purification of vicine and convicine from fababeans ( Vicia faba L.)

A procedure was developed for the simultaneous isolation of pure vicine [2,6‐diamino‐4,5‐dihydroxypyrimidine 5‐(β‐D glucopyranoside)] and convicine [2,4,5‐trihydroxy‐6‐aminopyrimidine 5‐(β‐D glucopyranoside)] from dehulled fababeans. The procedure involved the extraction of the glycosides with an ethanol‐water (70:30, by vol.) solution, concentration of the extract to a minimal volume and adjustment of the pH of the aqueous extract to 7.2. Mixed vicine and convicine crystals, which were formed over a period of from 1 to 4 days, were harvested by centrifuging and washed with water and ethanol. Vicine was readily obtained from the mixed crystals by extraction at a low pH and recrystallised by adjustment of the pH to neutrality. Convicine, which is relatively insoluble in an acidic medium, was solubilised in an alkaline solution and recrystallised at a neutral pH.