Estimation of the Chelating Ability of an Extract from Aronia melanocarpa L. Berries and Its Main Polyphenolic Ingredients Towards Ions of Zinc and Copper

Previously, we have revealed that prolonged administration of a polyphenol-rich 0.1% extract from the berries of Aronia melanocarpa L. (chokeberries) alone and under chronic exposure to cadmium influences the body status of zinc (Zn) and copper (Cu). The aim of this study was to evaluate, in an in vitro model, the chelating properties of the extract (0.05% and 0.1%) and its main polyphenolic ingredients (cyanidin 3-O-β-galactoside, chlorogenic acid, neochlorogenic acid, (+)-catechin, (−)-epicatechin, quercetin, and kaempferol) regarding divalent ions of Zn (Zn(2+)) and Cu (Cu(2+)) at pH reflecting physiological conditions at the gastrointestinal tract such as 2 (empty stomach), 5.5 (full stomach), and 8 (duodenum). The study has revealed that the extract from Aronia berries, as well as cyanidin 3-O-β-galactoside and quercetin, can bind Zn(2+) and Cu(2+), but only at pH 5.5. Moreover, kaempferol was able to chelate Zn(2+) at pH 5.5; however, this ability was weaker than those of cyanidin 3-O-β-galactoside and quercetin. The ability of the chokeberry extract to chelate Zn(2+) and Cu(2+) may be explained, at least partially, by the presence of polyphenols such as anthocyanin derivatives of cyanidin and quercetin. The findings seem to suggest that Aronia products, used as supplements of a diet, should be consumed before meals, and particular attention should be paid to adequate intake of Zn and Cu under prolonged consumption of these products to avoid deficiency of both bioelements in the body due to their complexation by chokeberry ingredients in the lumen of the gastrointestinal tract.