Evaluation of byproducts from the wine-making industry by identification of bioactive compounds

Byproducts obtained after wine production constitute an important source for the extraction of antioxidant compounds. Phenolic compounds showed a wide spectrum of biological actions for the human health, often associated with neuroprotective, cardioprotective, antimicrobial and other health-related effects. The aim of the present study was to determine the phenolic compounds content and antioxidant activity of grape marc from selected grapes from Iaşi vineyard. The total phenolic content of the extracts was measured using the Folin-Ciocâlteu method, with some modifications. The DPPH (2,2-diphenyl-1-picrylhydrazyl) assay was used to evaluate radical scavenging activity, by bleaching of purple methanolic solution of the stable radical. All extracts were able to reduce DPPH radical with different degrees of scavenging activity. The highest radical scavenging activity was determined for the extract obtained from Merlot and Fetească Neagră (98.142 μg/mL, and 115.78 μg/mL respectively), with positive correlation between scavenging activity on DPPH and total phenolic content. The total phenolic content varied among the analysed extracts, with a higher concentration in extracts obtained from Merlot, Fetească Neagră and Traminer rosé (2.42 GAE/mL, 1.45 GAE/mL and 1.24 GAE/mL respectively), followed by Sauvignon Blanc and Muscat Ottonel extracts with comparable amounts. The FRAP (ferric reducing antioxidant power) method relies on the color change of a complex with Fe+3 ion of the 2,4,6-tri(2-pyridyl) – 1,3,5-triazine (TPTZ) radical due to the reduction of the ferric ion to the ferrous iron (Fe+2) in this complex. The highest radical scavenging activity was determined in the extract obtained from Merlot and Fetească Neagră (1164.22 μM Trolox/100 mL and 782.09 μM Trolox/100 mL respectively), a positive correlation between scavenging activity determined by FRAP method and total phenolic content being observed.Statistical analysis showed a close relationship between content of phenolic compounds and antioxidant capacity, the marc of Merlot and Fetească Neagră had the highest contents of anthocyanins. The results suggested that grape pomace may be exploited as antioxindant source.