Phenolic content, volatile compounds and antioxidant activity in pooled propolis samples from Turkey and Poland

Propolis is one of the most used natural supplements, and its composition and biologically active properties vary from region to region. In this study, conducted as a case study, the phenolic profiles, volatile compounds and antioxidant activities of propolis samples from two different regions were compared. The phenolic compositions of the ethanol extracts were examined as total phenolic content (TPC) and total flavonoid content (TFC) and phenolic compositions. Phenolic compounds were analyzed using high-performance liquid chromatography-photo diode array (HPLC-PDA) according to the method using 25 phenolic standards. Antioxidant capacities were assessed using ferric reducing/ antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Volatile compounds were analyzed using headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). The average TPC and TFC values in the Polish and Turkish pooled propolis samples were determined as 187.16 ± 3.03 mg GAE/g and 44.69 ± 1.02 mg QUE/g and 198.09 ± 2.50 mg GAE/g and TFC 54.26 ± 0.70 mg QUE/g, respectively. While caffeic acid phenethyl ester (CAPE), myricetin, luteolin and hesperidin were high in the Turkish pooled propolis sample, p-coumaric acid, OH-benzoic acid, pinocembrin and apigenin were found high in the Polish pooled propolis sample. Approximately 133 volatile compounds were identified across both samples, with the Turkish pooled propolis sample demonstrating a notably higher presence of compounds such as verbenone, carveol, carvone, α-pinene, limonene, and β-eudesmol. The Turkish pooled propolis sample demonstrates a higher antioxidant activity in both methods due to its richer phenolic and volatile composition. In conclusion, the chemical composition and antioxidant properties of propolis are significantly influenced by the flora of its region of origin.