Antioxidant activity of white grape seed extracts on DPPH radicals

Abstract

Composition and antioxidant activity of grape seed extract (GSE) obtained from red grape varietes are very well documented, in contrast to the white varietes. This paper presents the results of polyphenols content of ethyl acetate extract of grape seeds, obtained from two white grape varieties, Italian Riesling and Zupljanka, and their antioxidant activity on the stable DPPH radical. The influence of the addition of GSE to raspberry juice on the DPPH radical was also examined. Content of total polyphenols in GSEs ranged between 81.6 and 82.8% (w/w), and the contetn of flavan-3-ols between 66.2 and 91.0% (w/w). HPLC results showed that the most abundant components in the extract were (+)-catechin and (-)-epicatechin for both grape varieties. All tested GSEs exhibited good antioxidant activity. IC50 values for the GSEs of Italian Riesling and Zupljanka were 0.79 and 0.95 mg sample/mg DPPH radical, respectivelly. Since the GSE of Italian Riesling possesed stronger antioxidant activity, it was used for further experiments. The IC50 value for raspberry juice was 4.18 mg raspberry juice/mg DPPH. The raspberry juice with addition of 0.60 ?g/mL of GSE showed antioxidant activity of 39.2%. The same juice with the threefold concentration of vitamin C (1.81 ?g/ml) exhibited similar antioxidant activity (33.9%). Antioxidant activity of the same amount of juice without added antioxidants was lower (15.7%). The results showed that the GSE of white varietes could be considered as a good functional food ingredient.Sastav i antoksidativne osobine ekstrakata semena iz sorti crnog grozdja su detaljno opisane u literaturi, dok su ekstrakti semena sorti belog grozdja manje ispitivane. U radu su prikazani rezultati odredjivanja sadrzaja polifenolnih jedinjenja i antioksidativna aktivnost etilacetatnog ekstrakta semena dve sorte belog grozdja, Italijanski rizling i Zupljanka, na DPPH radikale. Utvrdjen je uticaj dodatka ekstrakta, kao antioksidanta, u sok od maline na istu radikalsku vrstu. Sadrzaj ukupnih polifenolnih jedinjenja u ekstraktima iznosio je od 81,6 do 82,8 % (w/w), a sadrzaj flavan-3-ola je bio izmedju 66,2 i 91,0 % (w/w). Sadrzaji najzastupljenijih komponenata, (+)-katehina (32,17 ? 1,30%) i (-)-epikatehina (22,30 ? 0,72%), utvrdjeni su HPLC metodom. Svi ispitivani ekstrakti pokazali su dobru antioksidativnu aktivnost. Vrednost IC50 za ekstrakt semena grozdja sorte Italijanski rizling iznosila je 0,79, a za ekstrakt sorte Zupljanka 0,95 mg uzorka/mg DPPH. Posto je ekstrakt semena grozdja sorte Italijanski rizling pokazao bolju antioksidativnu aktivnost, on je koriscen za dalja ispitivanja. IC50 vrednost za sok od maline iznosila je 4,18 mg uzorka/mg DPPH. Sok od maline sa dodatkom ekstrakta od 0,60 ?g/ml pokazao je antioksidativnu aktivnost od 39,2%. Slicnu antioksidativnu aktivnost (33,9%) imao je i sok od maline sa dodatkom vitamina C u tri puta vecoj koncentraciji (1,81 ?g/ml). Antioksidativna aktivnost iste kolicine soka bez dodatka antioksidanata je bila znatno niza i iznosila je 15,7%. Navedeni rezultati ispitivanja ukazuju na mogucnost koriscenja ekstrakta semena sorti belog grozdja kao dobrog funkcionalnog dodatka.