Aksu Kalmuk, Nurşen2026-07-172026-07-172025https://hdl.handle.net/11494/6347This study presents the first comprehensive organ-based analysis in the literature in which the quantitative distribution of 25 phenolic compounds in the flower, leaf, and stem methanolic extracts of Hypericum montanum L. was evaluated and supported by antioxidant assays. Total phenolic and flavonoid contents were determined for each organ, and antioxidant capacities were assessed using DPPH, FRAP, and CUPRAC methods. The results revealed notable chemical differences among the plant organs. In the floral tissue, high levels of flavonoids such as epicatechin, catechin, hesperetin, and quercetin were detected, which corresponded well with the strong antioxidant activity observed in the CUPRAC and DPPH assays. Phenolic acids such as rosmarinic acid and 3,4-dihydroxybenzoic acid, which were abundant in the leaf tissue, were consistent with high FRAP values. These findings suggest that certain organs of the plant may have potential for inclusion in natural antioxidant-enriched formulations. Additionally, the phenolic composition data may offer preliminary insights into the chemotaxonomic differentiation of H. montanum from morphologically similar species. In this respect, the study provides supplementary evidence that could contribute to future taxonomic evaluations. Overall, the findings lay a foundation for more detailed investigations into the phytochemical and biological properties of H. montanum.eninfo:eu-repo/semantics/openAccessHypericumAntioxidant activityHPLC analysisPhenolic compoundsFlavonoidsChemotaxonomyArticle7323724910.51435/turkjac.1675184