Moving beyond the van Krevelen Diagram: A New Stoichiometric Approach for Compound Classification in Organisms

TLDR

Van Krevelen diagrams, which plot O/C versus H/C ratios, are commonly used to estimate compound classes in environmental samples, yet their categorical limits are poorly defined and overlap among classes is substantial. The authors aim to develop a more accurate compound classification for biological samples analyzed by high‑resolution mass spectrometry. They propose a multidimensional stoichiometric approach (MSCC) that evaluates C/H/O/N/P ratios across 130 000 elemental formulas, categorizing them into six main groups: lipids, peptides, amino sugars, carbohydrates, nucleotides, and phytochemicals. MSCC achieves over 98 % accuracy in classifying elemental formulas, markedly outperforming traditional van Krevelen‑based methods, and offers a robust tool for ecological stoichiometry and eco‑metabolomics.

Abstract

van Krevelen diagrams (O/C vs H/C ratios of elemental formulas) have been widely used in studies to obtain an estimation of the main compound categories present in environmental samples. However, the limits defining a specific compound category based solely on O/C and H/C ratios of elemental formulas have never been accurately listed or proposed to classify metabolites in biological samples. Furthermore, while O/C vs H/C ratios of elemental formulas can provide an overview of the compound categories, such classification is inefficient because of the large overlap among different compound categories along both axes. We propose a more accurate compound classification for biological samples analyzed by high-resolution mass spectrometry based on an assessment of the C/H/O/N/P stoichiometric ratios of over 130 000 elemental formulas of compounds classified in 6 main categories: lipids, peptides, amino sugars, carbohydrates, nucleotides, and phytochemical compounds (oxy-aromatic compounds). Our multidimensional stoichiometric compound classification (MSCC) constraints showed a highly accurate categorization of elemental formulas to the main compound categories in biological samples with over 98% of accuracy representing a substantial improvement over any classification based on the classic van Krevelen diagram. This method represents a signficant step forward in environmental research, especially ecological stoichiometry and eco-metabolomics studies, by providing a novel and robust tool to improve our understanding of the ecosystem structure and function through the chemical characterization of biological samples.