Selenosugars, a group of selenium-containing sugar metabolites that account for much of the selenium eliminated in human urine, have received a proposed scientific naming system designed to resolve more than two decades of confusion. In a new position paper, an international team of researchers has introduced a harmonized nomenclature, defined minimum analytical requirements for identifying these compounds, and proposed an updated model of mammalian selenium metabolism. The recommendations are intended to give researchers a common language for describing selenium metabolites and to reduce the risk of mistaking related molecules for one another.
Selenium is an essential trace element involved in antioxidant defense, thyroid hormone metabolism, immune regulation, and the function of numerous selenoproteins. Yet selenium can also become toxic when present in excessive amounts, making the control of its absorption, transformation, storage, and excretion biologically important. Selenosugars appear to occupy a central position in this balance. They are formed during selenium metabolism and are excreted in urine, where they represent major terminal products of selenium processing in humans. Similar compounds have also been detected in several animal species, suggesting that sugar-bound selenium may be a widespread strategy for managing the element.
The scientific problem is that the term “selenosugar” has not referred consistently to a single compound or structural class. Since these metabolites were first discovered and characterized in the early 2000s, different laboratories have adopted different names for closely related molecules, biosynthetic precursors, chemical derivatives, and urinary excretion products. In some cases, compounds with similar elemental compositions have been assigned different names, while distinct substances have been treated as though they were identical. Such inconsistencies complicate comparisons between studies and can make it difficult to determine whether researchers are observing the same metabolite, a modified form, or an intermediate in a metabolic pathway.
The new framework, led by Yasumitsu Ogra of Chiba University in Japan, establishes an operational nomenclature intended to preserve important structural information while remaining practical for routine scientific communication. The system uses a root symbol associated with the sugar scaffold and additional symbols that describe chemical modifications within the molecule. These modifications may distinguish different selenium-containing groups, oxidation states, or related structural features. Rather than relying on a collection of historical names, the proposed approach is designed to indicate how a molecule is built and where it fits within the broader family of selenosugars.
The researchers argue that a standardized name is only useful when it is supported by reliable chemical evidence. For that reason, the position paper also recommends a multi-stage analytical workflow for confirming selenosugar identities. One key component is high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry, or HPLC–ICP–MS. High-performance liquid chromatography separates individual metabolites in a complex biological sample, while ICP–MS detects selenium with high sensitivity and provides element-specific information. This combination can reveal which chromatographic compounds contain selenium and can support accurate quantification even when the metabolites are present at very low concentrations.
Element-specific detection, however, does not by itself establish the complete molecular structure. The recommended workflow therefore includes HPLC coupled with electrospray ionization tandem mass spectrometry, or HPLC–ESI–MS/MS. This method provides molecular-weight information and produces fragmentation patterns that can help identify the arrangement of atoms within a candidate metabolite. The researchers emphasize that accurate mass measurements, comparisons with authentic reference standards, and careful evaluation of molecular fragments are essential for avoiding false assignments. A compound that contains selenium may not necessarily be the specific selenosugar initially suspected from its chromatographic behavior.
For definitive structural validation, the authors identify nuclear magnetic resonance spectroscopy as the most powerful confirmatory technique when sufficient material is available. NMR can reveal the chemical environment of atoms within a molecule and provide information about the sugar ring, substituent positions, and connectivity of the selenium-containing group. The team also highlights the importance of documenting metabolite stability, because selenosugars may change during sample storage, preparation, or instrumental analysis. Taken together, selenium-specific detection, molecular mass spectrometry, authentic standards, accurate mass data, stability testing, and NMR form what the researchers describe as a practical “gold standard” for dependable selenosugar identification.
The paper also revises the way selenium metabolism is represented in mammals. In the proposed model, selenosugars are not minor side products but central terminal metabolites involved in selenium detoxification and urinary excretion. The framework incorporates recognized metabolic intermediates, protein-bound selenosugars, and conjugated selenium species to describe how selenium may be transported, temporarily stored, chemically transformed, and ultimately eliminated. This model places urinary selenosugars at the end of a regulated pathway that helps prevent excess selenium from accumulating in tissues while still allowing the body to use selenium for essential biological functions.
At the same time, the researchers stress that major questions remain unanswered. The enzymes responsible for producing many selenosugars have not been fully identified, and the biological reason for attaching selenium to sugar-based structures is still not completely understood. It is also unclear how strongly diet, genetics, disease, age, and exposure to different selenium compounds influence the pattern of selenosugars found in urine. Because selenium metabolites occur in humans as well as mammalian and non-mammalian animals, comparative studies could reveal which parts of the pathway are evolutionarily conserved and which reflect species-specific adaptations.
The authors say that consistent terminology and rigorous analysis will be particularly important as selenium research moves beyond cataloging metabolites and begins investigating their biological functions and clinical significance. A shared nomenclature could make datasets easier to compare, while the recommended analytical standards could improve reproducibility across laboratories. The updated metabolic framework may also help researchers study selenium homeostasis in disorders involving oxidative stress, nutrition, toxicology, or impaired excretion. By bringing analytical chemistry, biochemistry, toxicology, and systems biology into a single framework, the team hopes to transform selenosugar research from a fragmented field into a more coherent investigation of how organisms control one of their most chemically versatile trace elements.
Subject of Research: Not applicable; literature review and position paper on selenium metabolism and selenosugars.
Article Title: Selenosugars in Animals and Humans: Operational Nomenclature, Analysis, Occurrence, and Metabolic Pathways
News Publication Date: July 31, 2026
Web References: Chiba University news: https://www.cn.chiba-u.jp/en/news/ ; DOI: https://doi.org/10.1007/s12011-026-05268-2
References: Yasumitsu Ogra, Noriyuki Suzuki, Yasunori Fukumoto, Yu-ki Tanaka, Roger A. Sunde, Joanna Szpunar, and Ryszard Lobinski, “Selenosugars in Animals and Humans: Operational Nomenclature, Analysis, Occurrence, and Metabolic Pathways,” Biological Trace Element Research, DOI: 10.1007/s12011-026-05268-2.
Image Credits: Professor Yasumitsu Ogra, Chiba University, Japan; Dr. Ryszard Lobinski, CNRS-UPPA, France, and Warsaw University of Technology, Poland.
Keywords: selenosugars, selenium metabolism, selenium homeostasis, urinary metabolites, selenium speciation, HPLC–ICP–MS, tandem mass spectrometry, nuclear magnetic resonance, trace elements, toxicology, metabolomics, biological chemistry
