Glycaemic activity of chromium(III)–β-nicotinamide adenine dinucleotide phoshate complex and its presence in yeast extracts

Abstract

Two main stable chromium complexes were detected in the aqueous extract of Cr-rich yeast using high-performance liquid chromatographic (HPLC) separation on a reversed-phase RP-8 column and atomic absorption spectrometric detection of chromium. However, the complexes could not be separated and purified sufficiently to allow their reliable identification. Both complexes behaved like ionic or very polar substances with a weak affinity to the reversed-phase column. Yeast extract was then spiked with some synthetic Cr complexes which were prepared considering known data (UV spectra, molecular mass, etc.) on candidate glucose tolerance factor (GTF) compounds. Among the complexes tested, attention was paid especially to the complex of Cr^III with β-nicotinamide adenine dinucleotide phosphate (NADP), which accompanies one of two Cr complexes in yeast extract during the HPLC separation. The complex with a Cr: NADP stoichiometric ratio of 1 : 2 has not previously been reported. The complex was tested for its glycaemic activity using glucose tolerance tests on rabbits. Significant hyperclycaemia was caused in the animals. Considering that NADP is generally present in tissues of nearly all living organisms, its complexes with transient metals could play a very important role in oxidation–reduction processes of metabolic pathways.