Cyclodextrins as high-performance green co-solvents in the aqueous extraction of polyphenols and anthocyanin pigments from solid onion waste

Abstract

This investigation was carried out with the scope to examine three commonly used cyclodextrins (CDs), β-cyclodextrin (β-CD), methyl β-cyclodextrin (m-β-CD) and 2-hydroxypropyl β-cyclodextrin (HP-β-CD) as green co-solvents for the effective extraction of polyphenols and pigment from onion solid wastes (OSW). Efficiency appraisal was based on the “extraction efficiency index” (Iee), a parameter established to readily assess the ability of a CD to boost aqueous polyphenol extraction. m-β-CD was found to be the most efficient, giving Iee of 3.39 and 0.073 mg μmolCD−1 for total polyphenols and total pigments, respectively. Response surface optimization revealed that both m-β-CD and HP-β-CD required almost identical time and temperature conditions for maximized polyphenol recovery, but major differences were found for pigment extraction. β-CD was the least efficient in extracting total polyphenols, but it displayed a satisfactory effectiveness in pigment extraction. The antiradical activity and ferric-reducing power of the extracts generated with m-β-CD and HP-β-CD were comparable to those of hydroethanolic and hydroglycerolic extracts. Both these CDs were also more efficient than β-CD in extracting spiraeoside and quercetin, but β-CD exhibited higher efficiency for anthocyanin extraction. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.