39D-11

G. T. KROYER and E. Winkler. Institute of Food Chemistry and Technology, University of Technology, Getreidemarkt 9, Vienna, A-1060, Austria

In recent times, there is a growing interest in the food industry and in preventive health care in the development and evaluation of natural antioxidants from plant materials. Grape seeds contain considerable amounts of polyphenolic substances which have been reported to have antioxidant activity. The objective of this study was to quantify the total polyphenolic compounds and to evaluate the antioxidative and free radical scavenging properties of different extracts of seeds of white and red grapes. The ground seeds were dried and extracted individually with methanol, acetone and ethyl acetate. The obtained solid extracts were analyzed for their content of total polyphenols (Folin-Ciocalteu method). The antioxidant activities were determined in terms of their Anti-Radical Power (ARP) as assessed with the DPPH radical scavenging method (initiation step of oxidation), as well as their Antioxidant Activity Coefficient (AAC) as assessed with the b-carotene bleaching method in an oxygenated aqueous emulsion (propagation step of oxidation). For both methods, the methanol extracts of white grape seeds (ARP: 407, AAC: 790) and red grape seeds (ARP: 292, AAC: 657) proved to have the strongest antioxidative properties comparable in activity with ascorbyl palmitate and a-tocopherol, followed by the acetone extracts, whilst the ethyl acetate extracts showed relative poor inhibitory effectiveness. Generally, the individual seed extracts of white grapes showed significant higher antioxidant activity compared to red grape seed extracts, which is found to correlate with the respective content of total polyphenolic substances (methanol: 41 %, acetone: 16 %, acetyl acetate: 6 %). The results indicate that grape seed extracts, above all the methanol extract of white grape seeds, have remarkable antioxidative and radical scavenging properties in correlation with their content of total polyphenolic substances. An application as potent natural antioxidant additives for food products and as dietary supplements seems to be worth considering.