BACKGROUND: Phenolic compounds are the predominant ingredients in apple pomace. However, polyphenols from industrial apple pomace, which usually consists of several cultivars, have not been studied in detail. The present work focused on the antioxidant assay and HPLC analysis of polyphenol-enriched extracts from industrial apple pomace. RESULTS: Six fractions of apple polyphenols, API to APVI, were acquired through extraction and purification using absorbent macroporous resin. Fraction APIII, eluted by 40% aqueous ethanol, had the highest content of total phenolics (1.48 ± 0.03 g gallic acid equivalents g(-1) dry apple pomace), which consisted of chlorogenic acid, caffeic acid, syrigin, procyanidin B2, (-)-epicatechin, cinnamic acid, coumaric acid and quercetin. Antioxidant assays showed that APIII had the strongest antioxidant activity of DPPH radical scavenging rate (90.96% ± 10.23%), ABTS radical inhibition rate (89.78% ± 6.54%) and the strongest reducing power (8.30 ± 0.71 µmol Trolox equivalents kg(-1) dry apple pomace). It also indicated that procyanidin B2, chlorogenic acid, (-)-epicatechin and quercetin had stronger antioxidant capacity than other phenols. CONCLUSION: Our data suggested that extracts from industrial apple pomace were rich in phenols and exhibited potent antioxidant activity. Extraction of polyphenols from industrial apple pomace would bring a great benefit and improve development of apple juice and cider industries.
BACKGROUND: Phenolic compounds are the predominant ingredients in apple pomace. However, polyphenols from industrial apple pomace, which usually consists of several cultivars, have not been studied in detail. The present work focused on the antioxidant assay and HPLC analysis of polyphenol-enriched extracts from industrial apple pomace. RESULTS: Six fractions of applepolyphenols, API to APVI, were acquired through extraction and purification using absorbent macroporous resin. Fraction APIII, eluted by 40% aqueous ethanol, had the highest content of total phenolics (1.48 ± 0.03 g gallic acid equivalents g(-1) dry apple pomace), which consisted of chlorogenic acid, caffeic acid, syrigin, procyanidin B2, (-)-epicatechin, cinnamic acid, coumaric acid and quercetin. Antioxidant assays showed that APIII had the strongest antioxidant activity of DPPH radical scavenging rate (90.96% ± 10.23%), ABTS radical inhibition rate (89.78% ± 6.54%) and the strongest reducing power (8.30 ± 0.71 µmol Trolox equivalents kg(-1) dry apple pomace). It also indicated that procyanidin B2, chlorogenic acid, (-)-epicatechin and quercetin had stronger antioxidant capacity than other phenols. CONCLUSION: Our data suggested that extracts from industrial apple pomace were rich in phenols and exhibited potent antioxidant activity. Extraction of polyphenols from industrial apple pomace would bring a great benefit and improve development of apple juice and cider industries.