The Antioxidant Effects of a Polyphenol-Rich Grape Pomace ExtractIn VitroDo Not CorrespondIn VivoUsing Exercise as an Oxidant Stimulus

Abstract

Fruits, such as grapes, are essential food of the Mediterranean diet. Grape extracts have potent antioxidant and chemopreventive propertiesin vitro. Numerous studies have examined the effects of plant extract administration on redox status at rest in animals and humans but their results are controversial. However, there are no studies comparing thein vitroandin vivoeffects of plant extracts on oxidative stress using exercise as an oxidant stimulus. Thus, the aim of this study was to investigate whether a polyphenol-rich grape pomace extract of theVitis viniferaspecies possessesin vitroantioxidant properties and to examine whether these properties apply in anin vivomodel at rest and during exercise. Our findings indicate that the tested extract exhibits potentin vitroantioxidant properties because it scavenges the DPPH•and ABTS•+radicals and inhibits DNA damage induced by peroxyl and hydroxyl radicals. Administration of the extract in rats generally induced oxidative stress at rest and after exercise whereas exercise performance was not affected. Our findings suggest that the grape pomace extract does not behave with the same wayin vitroandin vivo.