Differential partitioning for purification of anthocyanins from Brassica oleracea L.

• Differential partitioning of anthocyanins and sugars could be successfully achieved by employing ATPE.
• Nearly 76% of sugars could be stripped by single step of ATPE.
• Nearly 96% of sugars could be removed by multistage extraction.
• Structural stability of anthocyanins after multistage ATPE has been confirmed.

Aqueous two phase extraction was employed as an alternate method for the downstream processing of anthocyanins. Polyethylene glycol (PEG) 4000/magnesium sulphate (14.8%/10.3% w/w) was found to be the most suitable system. Tie line length of 32.61% and volume ratio of 0.73 have resulted in maximum partitioning of anthocyanins to the PEG-rich phase (yield – 98.19%) and sugars to the salt-rich phase (yield – 73.16%). Multistage aqueous two phase extraction resulted in an increase in removal of sugars (to about 96.5%) with 91.9% yield of anthocyanins. The phase forming polymer (PEG 4000) was successfully separated from anthocyanins employing organic–aqueous extraction resulting in 2.3 fold increase in the concentration of anthocyanins. High performance liquid chromatography (HPLC)–Mass spectroscopy (MS)/MS was carried out to confirm the structural stability of anthocyanins.