Indigo and indirubin derivatives from indoles in Polygonum tinctorium tissue cultures

Substituted indoles (5-bromo-, 5-fluoro-, 5-chloro-, 5-hydroxy-, 4-methyl-, 5-methyl-, 6-methyl-, and 7-methylindole) were fed at 1 mM for 10 to 21 days into the tissue cultures of Polygonum tinctorium including cell suspension, root and shoot cultures. They were converted into the corresponding indirubin and indigo derivatives with the exception of 5-hydroxyindole. The yield ranged between 0.7-1.1 mg/g dried weight for indigos and 0.007-0.024 mg/g dried weight for indirubins. Presence of the corresponding indican derivatives in the shoot culture suggested that the pigment production proceeded through the indican formation.