2.7. Solid-phase extraction
The SPE material (Amberlite XAD7) was soaked with bidistillated
water and then loaded into the column. After that, the column
was rinsed with bidistillated water and the crude extract was applied.
The impurities were eluted with bidistillated water. Ten millilitres
of fractions of the eluate were collected until no soluble dry
solids were detected. After that, anthocyanins were eluted with
96% ethanol. To represent the elution profile of anthocyanins,
10 ml fractions were collected and analysed. The dense part of
the anthocyanin-containing ethanol was concentrated via rotary
evaporation at 50 C. After that, concentrated extracts were freeze
dried to obtain a powdered dry product. SPE was performed on
SUPELCO VISIPER system, connected to a vacuum pump (KNF
lab) with 50 ml glass cartridges. Dry extracts obtained after SPE
were kept at 18 C until analysed. Before the analyses, extracts
were dissolved in phosphate buffered saline pH 7.4 (PBS) in concentration
2 mg sample/1 ml PBS. The SPE procedure was repeated
three times for all berry extracts.