On the preparation of indoxyl red from indican and some new characteristics.

An indole compound with a strong purple-red color was produced by boiling a solution of indican under acidic conditions and purified by chromatographies on DEAE-650S Toyopearl TSK-gel and silica-gel columns. The purple-red compound purified was identified as indoxyl red, on the basis of FAB Mass, (13)C NMR, (1)H NMR, UV-visible spectra, and IR spectra. Although indoxyl red was first synthesized by Seidel(9) 70 years ago, very little information has been available on its characteristics. We repot here that the compound was purple-red colored at acidic pH and green at pH 13, and showed antiproliferative and cytotoxic activities to the mouse B cell lymphoma cell line NSF202.