Fruit extracts of 10 varieties of elderberry (Sambucus nigra L.) interact differently with iron and copper

Abstract

The fruits of elderberry, Sambucus nigra L. (Adoxaceae), are a rich source of cyanidin-based anthocyanins. However, despite the plethora of research on their potential health benefits, information on possible interactions with metals, in particular the two essential trace elements, iron and copper, is lacking.We tested the interaction of elderberry fruit extracts with these metals under different (patho)physiologically relevant pH conditions with cyanidin and cyanidin-3-glucoside as standards.Purified and standardized ethanolic extracts of 10 varieties of elderberry were tested for iron and copper chelating and reducing activities in different ratios (extract/metal) using standardized rapid spectrophotometry (ferrozine, hematoxyline and bathocuproinedisulphonate). The anthocyanin content was analyzed by HPLC.Cyanidin, its 3-glucoside and all extracts were able to chelate iron and reduce both metals. However, their copper chelating properties were low. The extract of ‘Haschberg‘ was the most potent metal chelator and more efficient than the standards under all tested pH conditions but its iron reducing properties were lower than those of the standards. The correlation between cyanidin-3-glucoside content, metal chelation and iron reduction suggests that the major effect of extracts was due to cyanidin-3-glucoside.All extracts interacted with iron and copper but the biological effect varied significantly from one extract to the other.