Phytochemical Profiling and Antioxidant Potential of Ultrasonic-Assisted Methanolic Extracts from Different Organs of Geranium glaberrimum

Geranium glaberrimum Boiss. & Heldr. is a Turkish endemic species with previously reported phytochemical and biological properties; however, comparative phytochemical and antioxidant data across different plant organs remain scarce. In this study, ultrasonic-assisted methanolic extracts obtained from the flower, leaf, stem, and root were characterized by determining total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities using six complementary assays, relative antioxidant capacity index (RACI), and LC–MS/MS phenolic profiling. A single extract was prepared from each organ, and analytical measurements were performed in technical triplicate. The leaf extract exhibited the highest TFC (53.40 ± 0.15 mg RE/g), whereas the flower extract showed the greatest TPC (252.63 ± 5.73 mg GAE/g). RACI values were highest for the leaf (0.58 ± 0.02) and flower (0.47 ± 0.08), followed by the stem (−0.29 ± 0.19) and root (−0.77 ± 0.04), reflecting their relative positions within the investigated extracts based on the integrated phytochemical parameters and chemical antioxidant assay results. LC–MS/MS profiling targeted 28 phenolic compounds, of which 27 were detected, with hesperidin, hyperoside, gallic acid, quercetin, protocatechuic acid, and kaempferol among the predominant constituents. The antioxidant assays revealed organ-dependent patterns, with flower and leaf extracts generally exhibiting higher radical-scavenging and reducing capacities than the root extract. Exploratory Pearson correlation and hierarchical clustering analyses, based on four organ-level observations, indicated associations between phenolic composition and chemical antioxidant capacity. These findings provide an initial organ-specific phytochemical and antioxidant characterization of G. glaberrimum and highlight the need for independent biological replication and further biological validation.