Abstract
Some compounds without apparent chelation sites have been shown to chelate cupric ions using the hematoxylin assay. Four different known reducing agents (hydroxylamine, vitamin C, trolox, reduced glutathione /GSH/) were selected for the study together with oxidized glutathione (GSSG).
All tested compounds behaved as cupric chelators in the spectrophotometric mildly competitive hematoxylin assay. In-depth analysis however showed that only GSH and GSSG were able to form complexes with both cupric and cuprous ions and only GSSG partly retained copper in its complexes in the more competitive bathocuproine assay.
All tested compounds with the exception of GSSG reduced Cu2+ ions. Compounds reducing copper such as antioxidants can give false positive results in the hematoxylin-screening assay.