Identification of cadmium-chelating compounds in plant-based foods using SEC-ICP-MS/MS and SEC-QTOF-MS

Cadmium (Cd) is a toxic heavy metal, and dietary exposure is a major health concern. Plant-based foods are significant contributors to cadmium intake, underscoring the importance of understanding how Cd is absorbed, transported, and accumulated in plant matrices. Various naturally occurring compounds—such as phytochelatins (PCs), metallothioneins (MTs), organic acids, and dietary fibers—can bind Cd, potentially reducing its bioavailability in the human body. PCs, in particular, exhibit a strong affinity for Cd and other heavy metals, forming stable chelates. MTs are cysteine-rich proteins known to sequester metal ions and protect plant tissues from metal-induced toxicity.

Although low molecular weight (LMW) chelators like PCs have been relatively well studied, high molecular weight (HMW) Cd-binding proteins remain poorly characterized in plants. Recent studies suggest that proteins ranging from 40 to 80 kDa may play a key role in cadmium detoxification. SEC-ICP-MS has previously been employed for Cd speciation, but its limited resolution and separation capacity can hinder the precise identification of individual Cd-binding compounds based solely on molecular weight.

In addition, essential trace elements such as iron, zinc, and calcium can influence Cd bioavailability by competing for binding sites. Therefore, comprehensive multi-elemental speciation is critical to understanding not only Cd binding but also the interactions and competitive dynamics of these elements in plant-based food matrices.

To optimize extraction efficiency of cadmium species from plant-based foods, the researchers employed a full factorial design of experiments (DOE), optimizing parameters such as extraction time and solvent composition (acetonitrile and methanol content). Extraction recoveries varied widely—from 2.3% to 72.3%—indicating diverse cadmium-binding affinities across food types.

The extracted compounds were separated chromatographically using two different SEC columns (Superdex 30 Increase and Superdex 200 Increase) and analyzed using ICP-MS/MS and QTOF-MS. This dual analytical strategy enabled the identification of distinct cadmium-chelating patterns, particularly among compounds in the 1–20 kDa molecular weight range.

Multielement speciation analysis further revealed the presence of proteins, phytic acid, phytochelatins, and other metabolites with cadmium-binding capabilities. These findings illustrate the complexity and diversity of Cd chelation mechanisms in plant-based foods.

This study emphasizes the importance of understanding cadmium speciation and the role of essential trace elements in modulating its bioavailability. By integrating multi-elemental analysis with optimized extraction and separation techniques, the researchers provide a more comprehensive view of Cd-binding behavior in plant matrices.

The authors believe their methodology represents a significant advancement in cadmium speciation analysis and offers a promising foundation for future studies on Cd bioaccessibility and risk mitigation in plant-based diets.

last time modified: June 13, 2025