A reliable, green and fast two-step solid-phase extraction methodology for the obtention of anthocyanin-rich extracts from different sources

During the last few years, researchers have been focusing of strategies to recover and purify anthocyanins, from simple liquid-liquid extractions to more advanced supercritical CO₂ extractions, however, with such a huge number of different sources, it's extremely hard to get a simple and fast methodology that fits several sources, not only by the structural nature of the anthocyanins but also by the presence of specific groups of natural compounds. Using simple methodologies like solid-phase extraction resins combined with the use of green solvents, represents a powerful economical and efficient strategy. In this work, we tested several sources of structurally distinct anthocyanins, including purple basil, purple cabbage, purple sweet potato, butterfly pea flower, cornflower and wild pansy, in different resins, to assess their efficiency in the obtention of anthocyanin-pure extracts using acidified water-ethyl acetate-ethanol and water-ethyl acetate-methanol. The results showed us that the combination of Oasis HLB® resin followed by a cation-exchange SPE with DSC-MCAX® resulted in high-purity anthocyanin extracts for all the cases. Also, the overall efficiency of the greener approach water-ethyl acetate-ethanol did not compromise the efficacy of the system when compared to methanol, encouraging of this solvent rather than less environmentally friendly and more toxic alternatives.