Identification and quantification of major polyphenols in apple pomace

Apple pomace from juice processing was investigated as a potential source of fine chemicals. Major compounds isolated and identified include epicatechin, caffeic acid, phloretin-2′-glucoside (phloridzin), phloretin-2′-xyloglucoside, 3-hydroxyphloridzin, quercetin-3-arabinoside (avicularin), quercetin-3-xyloside (reynoutrin), quercetin-3-galactoside (hyperin), quercetin-3-glucoside (isoquercitrin) and quercetin-3-rhamnoside (quercitrin). The isolation of 3-hydroxyphloridzin as a natural component in apple was novel and its chemical structure, as well as those of the other co-occurring polyphenols, were established by 1H and 13C NMR spectroscopy and by acid hydrolysis.