Assessment of the Pb and Cu in vitro availability in wines by means of speciation procedures

The speciation of Pb and Cu in white and red table wines was investigated, in order to estimate their respective bioavailability to man. For this purpose, wines were subjected to in vitro gastrointestinal digestion, and the following properties were studied in the wines and in their gastric and intestinal digests: (1) the average conditional stability constant (Kav) of the strongest complexes (those inert to cathodic voltammetry) and of the respective ligand concentration (CCinert); (2) the distribution of the metal among the different bands of reverse phase high performance liquid chromatography (RP-HPLC) (groups of compounds of different molecular weight and/or polarity); (3) the total metal concentration and metal present in the soluble and in the dialyzable fractions of the digest. The CCinert of the red wines and the respective digests were much greater than those of the white wines and their digests. The conditional stability constants of the strongest soluble complexes after the digestion ranged between 5.9 and 6.1 for Pb. These parameters could not be determined for Cu. After the digestion the dialyzable metal fraction (a relative index of the metal potentially available for interaction with the inner biologic ligands) was only 16% of the total Pb in red wine, 62% in white Verde and 75% in white wine. For Cu the dialyzable metal fraction was 45% of the total metal in red wine, 64% in white Verde and 98% in white wine.