Dietary chromium - forms and availabilities

Area of Science:

• Biochemistry
• Environmental Science
• Plant Physiology

Background:

• Chromium is an essential trace element, but its chemical forms and bioavailability in plants are not fully understood.
• Plants can accumulate chromium from the environment, necessitating research into its metabolic fate and nutritional implications.

Purpose of the Study:

• To characterize the naturally occurring chromium compounds in plants.
• To investigate the stability and absorption of plant-derived chromium compounds in a mammalian gastrointestinal system.

Main Methods:

• Quantification of total chromium using flameless atomic absorption spectrophotometry.
• Molecular weight determination of chromium compounds via Sephadex G-25 gel filtration.
• In vivo and in vitro radioactive chromium tagging and tracking.
• Analysis of gastrointestinal tract integrity and absorption in rats.

Main Results:

• Naturally occurring plant chromium eluted at approximately 2600 daltons, forming a stable, anionic complex with an organic ligand.
• Only trivalent chromium (Cr(III)) was found in the organic complex, indicating plant bioreduction of hexavalent chromium (Cr(VI)).
• Plant chromium compounds remained intact throughout the gastrointestinal tract, with partial absorption (approx. 30%) in rats, primarily in the large intestine.

Conclusions:

• Plants synthesize stable, low-molecular-weight Cr(III) complexes that are bioavailable.
• The plant's ability to reduce Cr(VI) to Cr(III) is crucial for forming these stable, absorbable compounds.
• Dietary plant chromium exhibits significant gastrointestinal stability and absorption, highlighting its nutritional relevance.