Partial purification of anthocyanins from Brassica oleracea (red cabbage)

Red cabbage has a high content of anthocyanin and it may become an important source of this pigment. Common extraction methods are not selective, and a great quantity of sugar is co-extracted with the dye. This work used adsorption-desorption process on Amberlite XAD7 and Sephadex LH20 resins to partially purify anthocyanins present in the whole juice of red cabbage. Both resins succeeded to purify anthocyanins, producing solutions with up to 0.5 g L-1 of sugars from an initial concentration of more than 25 g L-1. Using Amberlite XAD7 it was possible to recover 24 to 95% of the dye initially found in the whole juice while 11 to 56% was recovered using Sephadex LH20. The kinetics of adsorption of the dye on Amberlite XAD7 was described according to a pseudo-second-order model, and the sorption equilibrium was well described by the Freundlich isotherm. The adsorption enthalpy was -17.13 kcal mol(-1), indicating a possible chemical adsorption.