In this study, fruit and vegetable wastes and by-products were tested for polyphenol content and their
antioxidant activity. The highest content of polyphenols as assessed by the Folin–Ciocalteu assay was
the hot-water extract of grape seed, followed by the ethanol extract of buckwheat hull. The highest antioxidant
activity measured by 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assays was also detected in the hotwater
extract of grape seed, followed by the ethanol extract of immature prune. Most of samples showed
protective effects against oxidative stress induced by 2,20
-azobis-(2-amidinopropane) dihydrochloride
(AAPH) peroxyl radical generator in African monkey kidney (MA 104) cells. Samples containing high
amounts of phenolics (more than 30 mg ChAE/g) generally showed high antioxidant activity and a protective
effect against AAPH-induced oxidative stress. This study demonstrates that fruit and vegetable
wastes and by-products are good sources of high amounts of phenolics with antioxidant properties.