Phenolic contents, in vitro antioxidant activities and biological properties, and HPLC profiles of free and conjugated phenolics extracted from onion, pomegranate, grape, and apple

This study quantified the free and conjugated phenolic content of extracts from selected Liliaceae (white and red onion), Punicaceae (red and pink pomegranate), Vitaceae (zini, red globe, and baladi grape), and Rosaceae (yellow and red apple) cultivated family plants and evaluated their antioxidant activities and beneficial properties toward diabetes and hypertension. Free and bound phenolics were extracted from plants, and total phenolic contents were evaluated. Antioxidant activities were assessed, as well as the inhibitory effects of angiotensin I-converting enzyme (ACE) and α-amylase and α-glucosidase activities. Liquid chromatography–mass spectrometry/mass spectrometry (LC–MS/MS) measured the individual phenolic content in both free and bound extracts. The free phenolic contents in the selected plants were higher than bound phenolic contents, except for in zini and red globe grapes. In onion, the highest antioxidant activity was observed in the bound phenolic extract (49.6–56.9%). In pomegran...