engleski

Antioxidant activity of selected wines from Dalmatia (Croatia)

Among the fruits and vegetables commonly consumed, grapes and their associated products including wine, juice and raisins may be the most important source of our dietary catechins and anthocyanins. In this study the reducing power of selected wines and pure (+)-catechine was determined using ferric reducing/antioxidant power (FRAP) assay. Radical scavenging potential was investigated using &#945; , &#945; -diphenyl-&#946; -picrylhydrazyl (DPPH) radical scavenging, and &#946; -carotene bleaching (BCB) methods. Six red and four white wines from different grape cultivars were analyzed. Total phenols in wines were determined with official AOAC procedure using Folin-Ciocalteu reagent. Flavonoids were determined using precipitation with formaldehyde. The anthocyanin content in wines was determined using bisulfite bleaching method. Catechins, as main reactants with reactive phloroglucinol moiety in wines, were reacted with vanillin and resulting colored compound was quantitatively determined. We tested 10 selected wines with controlled geographical origin: six red wines (Dingač, Babić, Cabernet Sauvignon, Farros, Faros barique, Merlot) and four white wines (Maraština, Pošip, Traminac, Graševina). The total phenol content, flavonoids, anthocyanins and catechins in wines were determined spectrophotometrically. Red wines had much higher total phenol, flavonoid, anthocyanin and catechin content than white wines, as expected. There was no significant difference between nonflavonoids phenols in red and white wines. Unpaired test with two tailed p-values showed highly significant difference between FRAP, DPPH, and BCB of red and white wines (p<0, 001). Different reducing/antioxidant power of red and white wines was elucidated in view of their different phenolic composition. All analysed wines demonstrate strong antioxidant capacity with FRAP test. The average FRAP of red wines was almost 10-fold higher than the average FRAP of white wines. The FRAP dose response of (+) catechin in aqueous solutions was linear up at least 1, 000 mM (+)-catechin. The relative antioxidant efficiency of (+)-catechin was 2.0 in FRAP assay, same as for ascorbate and Trolox. The reducing ability of red wines can be directly correlated with its flavonoid and catechin concentration. Determination of FRAP can be useful tool in evaluation of antioxidant activity of phenolic rich beverages, plant extracts and pure molecular antioxidants.

Antioxidant activity; wine; (+)-catechin; flavonoids; ferric reducing/antioxidant power; &#945;; &#945; -diphenyl-&#946; -picrylhydrazyl; &#946; -carotene bleaching

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