Enhancement of the solubility of organic dyes in aqueous ionic solvents doped with surfactants

•Indigo, alizarin and curcumin dissolve in the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulphate.•Indigo, alizarin and curcumin dissolve in the tetrabutylammonium acetate/lactic acid eutectic mixture.•Adding water or surfactant to the ionic solvents does not significantly affect the solubility of the natural dyes.•Cation-π interactions explain the solubility of indigo. This interaction is enhanced when the ionic solvents contain water.•Indigo dissolves very well in the hydrophobic cores of micelles formed in ionic media.