Methionine restriction and selenium supplementation are recommended because of their health benefits. As a major nutrient form in selenium supplementation, selenomethionine shares a similar biological process to its analog methionine. However, the outcome of selenomethionine supplementation under different methionine statuses and the interplay between these two nutrients remain unclear. Therefore, this study explored the metabolic effects and selenium utilization in HepG2 cells supplemented with selenomethionine under deprived, adequate, and abundant methionine supply conditions by using nuclear magnetic resonance-based metabolomic and molecular biological approaches. Results revealed that selenomethionine promoted the proliferation of HepG2 cells, the transcription of selenoproteins, and the production of most amino acids while decreasing the levels of creatine, aspartate, and nucleoside diphosphate sugar regardless of methionine supply. Selenomethionine substantially disturbed the tricarboxylic acid cycle and choline metabolism in cells under a methionine shortage. With increasing methionine supply, the metabolic disturbance was alleviated, except for changes in lactate, glycine, citrate, and hypoxanthine. The markable selenium accumulation and choline decrease in the cells under methionine shortage imply the potential risk of selenomethionine supplementation. This work revealed the biological effects of selenomethionine under different methionine supply conditions. This study may serve as a guide for controlling methionine and selenomethionine levels in dietary intake.

To address the challenges posed by extensive sample pretreatment and significant matrix interference in conventional metal quantification methods for cyanobacterial culture media, an automated online metal capture and enrichment system was developed and integrated with inductively coupled plasma mass spectrometry (ICP-MS). This system enabled the simultaneous determination of nine metal elements—Cd, Pb, V, Mn, Fe, Co, Ni, Cu, and Zn—within the culture medium. Through systematic optimization and validation, the method demonstrated exceptional analytical performance: calibration curves for all analytes exhibited correlation coefficients (r) exceeding 0.999; repeatability tests yielded relative standard deviations (RSD) below 3% (n = 6); and recoveries at low, medium, and high spike levels ranged from 93.98% to 108.70%. The procedure is characterized by simplicity, high automation, low detection limits, and robust accuracy, making it an effective platform for multi-element contamination monitoring and metal metabolic studies in cyanobacterial cultivation. This approach holds significant potential for applications in algal resource utilization and environmental restoration.

A derivatisation-free HPLC–MS/MS method was developed and validated for the simultaneous quantification of selenium- and sulphur-containing amino acids in soybean leaves, and applied to a 3 × 3 factorial hydroponic experiment probing selenium–sulphur metabolic interactions. The method resolves five biologically informative analytes (Cys₂, SeCys₂, MeSeCys, Met, SeMet) within 1.5 min through multiple reaction monitoring (MRM). Ultrasound-assisted extraction (UAE) of the free fraction was jointly optimised for both analyte classes by the response-surface methodology; enzymatic hydrolysis of the extraction residue recovered the protein-bound fraction on the same platform. Limits of detection ranged from 0.036 to 0.556 µg L⁻¹, intra-day relative standard deviations were below 5%, and spike recoveries fell between 92.3 and 117.4%. Free SeAA and SAA pools were negatively correlated across the nine treatments (R² = 0.83), consistent with competitive Se–S assimilation, whereas bound pools were positively correlated (R² = 0.89), reflecting proportional protein-level incorporation. A regime of 1–5 mM of sulphate with 20 µM of selenite yielded the highest bound organo-Se with near-normal growth, providing leaf-level evidence that may inform future seed-focused studies aimed at Se-enriched soy-protein ingredient development.