Production of indoxyl derivatives in indole-supplemented tissue cultures of Polygonum tinctorium

A red pigment produced in the suspension, root and, shoot cultures of Polygonum tinctorium. Ait. (Polygonaceae) upon feeding of indole was identified as indirubin by comparison with the authentic compound obtained from the leaves of the plant. Indole-5-d was specifically incorporated into the pigment to form indirubin-5,5'-d(2) when fed to the cultures. Tryptophan feeding did not cause the accumulation of the pigment. The dilution of the fed indole with the endogeneous indole was about zero, ten, and thirty-five percent for the suspension, root, and shoot cultures, respectively. The feeding of indole to the suspension and root cultures suppressed the biosynthesis of indigo thus resulting in the production of indirubin. However, the fed indole was equally well incorporated into indigo and indirubin in the shoot culture.