Chromium Coordination Compounds of Pyridoxal and Nicotinic Acid: Synthesis, Absorption and Metabolism

Abstract

The poor gastrointestinal absorption of inorganic chromium has hampered study of the bioavailability, biodistribution and function of this essential trace element. New coordination compounds of Cr(III) — most notably the Schiff base complexes of pyridoxal, dipeptides and nicotinic acid — have been synthesized and characterized for metabolic studies in mice. Data are presented to document the whole‐body absorption, excretory pathways and organ distribution of orally administered ⁵¹Cr complexes. These compounds are well absorbed but retention is low because of rapid urinary excretion. The liver accumulates more Cr from the pyridoxylidene complexes than from inorganic or other coordination compounds. These results suggest that Schiff base chelates potentiate the absorption of Cr by cells of the intestine, kidney and liver. Coordination by nicotinic acid increased the stability of the Schiff base chelates but did not affect the biodistribution significantly. The relationship of these complexes to the “glucose tolerance factor” is discussed.