Determination of volatile compounds and antioxidant properties of summer linden (Tilia platyphyllos Scop.) at different harvesting times

This study aimed to determine the volatile compound profile and antioxidant activity levels of Tilia platyphyllos Scop., which naturally grows in the Sindel Plateau of Şarkikaraağaç district, Isparta province, during the 2022 vegetation period. Plant samples were collected during three distinct phenological stages (pre-flowering–June, flowering–July, and post-flowering–September). Volatile compound analyses were conducted using Solid Phase Microextraction (SPME) and Gas Chromatography-Mass Spectrometry (GC-MS), and compound identification was performed using the Wiley, NIST Tutor, and FFNSC libraries. A total of 54 compounds were identified in the pre-flowering stage, 42 during the flowering stage, and 51 in the post-flowering stage. Hexane was the dominant compound across all three stages, while Allyl bromide and Carvacrol appeared at varying concentrations. Notably, Carvacrol reached a concentration of 10.27% in the post-flowering stage, indicating increased biosynthesis during this period. Antioxidant activity was assessed using DPPH and CUPRAC assays, revealing significant variations in phenolic content and antioxidant capacity across the phenological stages. The post-flowering stage exhibited the highest values in both total phenolic content and CUPRAC activity. These findings indicate that T. platyphyllos demonstrates phenologically dependent biochemical compositions, and the post-flowering stage represents the most suitable harvest time in terms of medicinal and pharmacological potential.