Extraction of Indigo dye from Couroupita guianensisand its application on cotton fabric

Couroupita guianensis (Cannon ball tree) flowers and fruits are known to contain indigotin and indirubin. In this study an attempt is made to optimize the period for effective extraction of indigo from Couroupita guianensis fruit and application of the crude extract on the cotton fabric. Fermentation of the Couroupita guianensis fruit pulp for 5 days gave intense bluer pigment and hence was selected as the optimum period for fermentation. Major colouring components from Couroupita guianensis fruit extract were separated by thin layer chromatography using single solvent system, chloroform; which gives three pigments, violet, blue and pink with the R f values of 0.88, 0.57, and 0.25 respectively. The R f values, the wavelength of maximum absorption from UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectrum and 1 H Nuclear magnetic resonance ( 1 H NMR) spectrum of blue pigment matched with that of synthetic indigo standard and that of the pink pigment matched with reported values of indirubin which is an isomer of indigotin. The % purity of indigo dye was found to be 26.46%. Dyeing of cotton fabric was carried out with the crude dye powder which gave comparable fastness properties vis-a-vis synthetic indigo.