Influence of solvent and temperature on extraction of phenolic compounds from grape seed, antioxidant activity and colour of extract

P>This study was aimed to investigate the influence of solvent (water and ethanol in concentration: 50%, 70% and 96%) and extraction temperature (25-80) degrees C on polyphenols extraction of grape seed (Vitis vinifera L. cv. Frankovka) cultivated in Eastern Croatia. The best results were reached using 50% ethanol at 80 degrees C. The most abundant individual polyphenolic compound was catechin which makes the average of 45.11% of the total phenolic content followed by epicatechin (34.45%), procyanidin B-2 (12.90%), gallic acid (5.34%), gallocatechin (1.58%), epicatechin gallate (1.01%). The antioxidant activity of extracts was determined by DPPH-method and it was highly dependent on extraction solvent and temperature. The total extractable proanthocyanidins content of extract had the highest positive correlation (r = 0.994) with antioxidant activity, which indicated that these compounds might be the most important antioxidant in examined grape seed extracts. Relationship between phenolic content and colour of extracts was observed.