The parameters for the extraction of an indigenous dyestuff from Lonchocarpus cyanescens leaves and its
spectroscopic characterization are discussed. The extraction was achieved by cold maceration in alkaline
Na2S2O4.solution. The IR spectra identified the presence of the following active functional groups; υ(O-H) and
υ(C-O) stretching of primary and secondary alcohols as well as υ(N-H) and υ(C-N) stretching of an aromatic
amine. These functional groups are similar to those associated with synthetic indigo dyes used in dyeing denim
jeans. Refinement of the crude dyestuff is achieved by precipitation with acid leaving the noxious principles in
solution. The variation of yield of dye with alkalinity is consistent with the dye existing as an insoluble ketal form
in the leaves which is reduced with hydrosulfite to a sparingly soluble leuco form. This leuco form is converted to
a more soluble salt species by addition of base.
Keywords: Vegetable indigo dye, solvent extracti