Ultrasound‐assisted extraction and preliminary purification of proanthocyanidins and chlorogenic acid from almond ( P runus dulcis ) skin

An aqueous solution of polyethylene glycol ( PEG ) as a green solvent was employed for the first time to develop the ultrasound‐assisted extraction of proanthocyanidins ( PA ) and chlorogenic acid ( CA ) from almond skin. The optimized extraction parameters were determined based on response surface methodology, and corresponded to an ultrasound power of 120 W, a liquid‐to‐solid ratio of 20:1 (mL/g), and a PEG concentration of 50% (v/v). Under these optimized conditions, the extraction yields of PA s and CA from almond skin were 32.68 ± 0.22 and 16.01 ± 0.19 mg/g, respectively. Compared with organic solvent extraction, PEG solution extraction produced higher yields. Different macroporous resins were compared for their performance in purifying PA s and CA from almond skin extract. Static adsorption/desorption experimental results demonstrated that AB ‐8 resin exhibits excellent purification performance at pH 4. Under the optimized dynamic adsorption/desorption conditions on the AB ‐8 column, the total recovery of purification for PA s and CA was 80.67%. The total content of PA s and CA in the preliminarily purified extract was 89.17% (with respective contents of 60.90 and 28.27%).