Determination of biologically interesting polyphenols from grapes, wines and vinification byproducts of Greek origin-assessment of their in vitro antioxidant activity

During the last decades there has been an increasing interest on the antioxidant properties and the potential health effects of wine and grapes. In this regard, various products (and byproducts) obtained from various native Greek grape varieties were studied, in respect to their polyphenolic content and antioxidant activities. More specifically, polyphenol-rich extracts –obtained by an optimized ultrasound extraction procedure– from respective grape berries, seeds, skins, stems and pomace, as well as wine samples, were assayed using HPLC-DAD and photometric methods. In addition, their antioxidant activities were evaluated with the following four different assays (modified to be used in a high throughput approach): DPPH^. radical scavenging assay, FRAP assay, LDL oxidation assay and the Intracellular ROS assay.

The assessment results indicated that in all cases, both seed and stem samples possess the highest Total Polyphenolic Content (TPC) and the best antioxidant activities. Furthermore, the observed good correlation between the antioxidant activities evaluated as the LDL oxidation inhibition and the Intracellular ROS assays are indicative of possible in vivo antioxidant activity of the extracts. The present study reveals the considerable antioxidant potential of the Greek grapevine products and the possibility of the exploitation of the use of vinification byproducts for the production of high added value natural products and/or extracts.