Abstract
Euphorbia yaroslavii Poljakov. is a rare plant species endemic to Kazakhstan whose phytochemical composition has remained largely unexplored. This study presents the first organ-specific phytochemical and GC-MS characterization of the leaves, stems, and roots of this species. Quantitative analyses indicated pronounced metabolic differentiation among plant organs. Roots were characterized by high contents of total phenolics (58.2 ± 2.5 mg GAE/g DW), coumarins (2.48%), and mineral components (total ash 13.22%), while leaves exhibited the highest tannin content (2.35%). The maximum flavonoid content was observed in roots (0.27%), whereas stems contained the highest level of ascorbic acid (0.70 mg/g DW). GC-MS profiling tentatively identified 68 compounds in leaf extracts, 65 in stem extracts, and 39 in root extracts. Root extracts were dominated by fatty acids and triterpenoid-sterol constituents, including octadecanoic acid (18.9%), hexadecanoic acid (17.5%), β-amyrin (5.2%), and lanosterol (4.9%). Overall, the results indicate organ-specific metabolic specialization in Euphorbia yaroslavii Poljakov. and provide a reliable phytochemical baseline for future bioactivity-oriented and conservation-related studies.