Comparison of zinc species in two specimens of edible plants and their fate in the human gastrointestinal tract

Abstract

The objectives of this work were to get information on Zn species in two different specimens of edible plants (pumpkin seeds and iceberg lettuce) and simulation of their behavior in the human gastrointestinal tract. An array of analytical techniques was used to aid in this research: ultrasound-assisted variable volume extraction, size exclusion chromatography (SEC), and physiologically based extraction tests (PBETs); elemental detection was performed by inductively coupled plasma-mass spectrometry (ICP-MS). Results show that pumpkin seeds and iceberg lettuce have different Zn species fingerprints (in water extracts) with a high (ca. 70 %) low-molecular-weight fraction (ca. 500 Da) in iceberg lettuce and a high (ca. 60 %) intermediate/high-molecular-weight fraction (10–20 kDa) in pumpkin seeds. When these Zn species are subjected to conditions simulating the human stomach (pH ~ 2) complete scrambling to their basic ionic form (Zn2+) takes place. Under conditions simulating the digestion in the intestines (pH ~ 7) formation of insoluble Zn complexes occurs, especially for pumpkin seeds, which may be related to antinutrients like naturally present phytate, leading to reduced Zn bioaccessibility in the small intestine.