Amberlite xad 16 resin

The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, hydroxymethylfurfural, potassium persulfate, 2,4,6-tris(2-pyridyl)-s-triazine, and Trolox^® were purchased from Sigma-Aldrich (Buchs, Switzerland). Maltodextrin and Amberlite XAD-16 resin were supplied by Brenntag (Kędzierzyn-Koźle, Poland). Cyanidin-3-O-glucoside, peonidin-3-O-rutinoside, quercetin-3-O-glucoside, quercetin-3-O-rutinoside, p-coumaric, and ferulic acid were obtained from Extrasynthese (Lyon, France). Chlorogenic and neochlorogenic acids were from TRANS MIT GmbH (Giessen, Germany). Acetonitrile for UPLC (gradient grade) and ascorbic acid were from Merck (Darmstadt, Germany). UPLC grade water prepared using the HLP SMART 1000s system (Hydrolab, Gdańsk, Poland) was additionally filtrated through a PTFE 0.22 µm membrane filter (Millex Samplicity Filter, Merck, Darmstadt, Germany) before use.

The fresh pomegranate fruit Punica granatum L. (cultivar Mollar de Eche) was delivered from Spain. The peels were collected, dried, and shredded in Thermomix. Subsequently, the obtained peel powder in the total amount of 1 kg was extracted and reextracted twice with 50% ethanol in an ultrasonic bath for 25 min. After the extraction procedure, the mixtures were centrifugated, and the supernatants were filtered. The resulting filtrate was concentrated by a Rotavapor rotary evaporator in a water bath at 40 °C. The concentrated extract from pomegranate peel was passed through the column filled with Amberlite XAD-16 resin (Brenntag, Essen, Germany) and eluted with distilled water to remove the organic acids, sugars, and other compounds. The polyphenol elution procedure was carried out with an 80% aqueous ethanol solution. Afterward, the gathered fractions were dried in an SPT-200 vacuum oven (Zeamil, Krakow, Poland).