Correlation between the phenolic content and DPPH radical scavenging activity of selected croatian wines

The Folin-Ciocalteu (FC) test and cyclic voltammetry (CV) at a glassy carbon electrode were used to quantify phenolic antioxidants in a set of 17 Croatian wines and express them in gallic acid (GAE) and catechin equivalents (CE). The total phenolic index (TPI) values for red wines expressed in GAE ranged from 18.851 to 26.905 mM, while TPI for white wines ranged from 1.722 to 2.869 mM. The levels of phenolics derived from CV measurements were markedly lower than those of TPI, since these values include only those phenolic compounds that get oxidised up to 500 mV and contain ortho-diphenol and triphenol groups. The free radical scavenging ability of the same set of wines was evaluated according to the Brand-Williams assay and expressed in equivalents of catechin, gallic acid, vitamin C and Trolox. Ivan Dolac barrique 2002 exhibited the highest antioxidant activity. The DPPH radical scavenging ability of the wines was also evaluated and correlated to the TPI values. Better correlation was observed between the TPI and the antioxidant activity for red wines (r(2)=0.826) as opposed to white wines (r2=0.686). The highest correlation (r(2)=0.970) was found between the TPI and the antioxidant activity measured when the whole set of samples was considered.