Polyphenolic profiling of Euphorbia cardiophylla, an endemic Turkish species, using Liquid chromatography-High resolution Orbitrap mass spectrometry and investigating its biological activity

• The first polyphenolic profile of Euphorbia cardiophylla with LC-HRMS • Leaves contained higher phenolic levels than roots. • Key phenolics indicate strong antioxidant potential. • Leaf extract showed superior antioxidant capacity. • Euphorbia cardiophylla as a bioactive-rich endemic with pharma/nutraceutical potential. This study used LC-High-resolution Orbitrap mass spectrometry (LC/HR Orbitrap-MS) to comprehensively investigate the phenolic compound profile and biological activities of Euphorbia cardiophylla Boiss. & Heldr. a species endemic to Türkiye. The leaf and root methanol extracts of the plant were evaluated, and their total phenolic (TPC) and total flavonoid (TFC) contents were determined using various antioxidant tests (DPPH, ABTS and CUPRAC). The findings revealed that the leaf extract contained significantly higher levels of phenolic compounds than the root extract, with TPC and TFC values of 125.64 ± 6.25 mg GAE/g and 49.42 ± 1.89 mg QE/g, respectively. Antioxidant activity tests showed that the leaf extract had much higher capacities for DPPH (309.04 ± 2.64 mg TE/g), ABTS (481.11 ± 9.12 mg TE/g) and CUPRAC (787.86 ± 15.09 mg TE/g) than the root extract. Analysis using UHPLC-Orbitrap®-HRMS has revealed the presence of compounds such as rutin hydrate (19,351.87 µg/g), quinic acid (31,473.66 µg/g), isoquercitrin (11,546.45 µg/g), astragalin (5,472.01 µg/g) and gallic acid (1,459.39 µg/g) at high levels in the E. cardiophylla plant. These results demonstrate that E. cardiophylla has a high phenolic content and strong antioxidant properties, suggesting that it could be a valuable source of natural bioactives for use in pharmaceuticals and nutraceuticals.