β-Carboline Alkaloids from Ribes nigrum L.

From Ribes nigrum L. two β-carboline alkaloids (deshydroxymethyl flazin (1) and flazin methyl ether (2)) could be isolated in minute amounts. The structure elucidation is described. The two compounds are present in the freshly pressed juice, but they are also formed during storage of the juice by condensation of tryptophane with ascorbic acid or its degradation products. This could be shown by adding 14C-labelled ascorbic acid to the juice. After four weeks’ incubation radioactive 1 and 2 could be isolated.