Impact of defatting process on antioxidant potential of grape seeds

Abstract

Grape seeds contain a wide range of phenolic compounds responsible for its health promoting effects. Interest for grape seed utilization has increased significantly along with a growing recognition that present biologically active compounds were not completely isolated during the extraction process. Numerous studies have been conducted in order to achieve the best extraction recovery. Nevertheless, there is still a question concerning the pretreatment of grape seeds. The aim of the present study was to investigate the impact of defatting process on total polyphenol content and antioxidant activity of grape seed extracts. For that purpose seeds were obtained from eight different grape varieties. Extraction with 70 % ethanol was performed on both, crude and defatted seeds (lipid fraction was removed by Soxhlet method of extraction). Determination of total phenolic content (TPC) was done using Folin-Ciocalteu assay. Antioxidant activity was investigated through four different tests (FRAP, CUPRAC, DPPH and ABTS) and obtained results were combined in unique Antioxidant Composite Index (ACI). TPC values ranged from 50.48 to 121.06 and from 38.04 to 108.17 mg GAE/g dry weight for crude and defatted grape seed extracts, respectively. Higher phenolic content determined in extracts obtained from crude seeds could be explained by the presence of lipophilic biologically active compounds in non-removed lipid fraction. Discrepancies between varieties are presumably present due to different morphological properties of seeds, environmental and agricultural conditions. Concerning antioxidant activity, all tests were significantly correlated with TPC, suggesting the strong contribution of phenolic compounds to this biological activity.