Investigation of chemical content and biological activities of northern Iraqi propolis

This study provides a comprehensive investigation of the chemical composition and biological activities of propolis samples collected from four geographically distinct regions in Northern Iraq, namely Erbil, Mosul, Duhok and Sulaymaniyah. With advanced chromatographic and spectrophotometric methods, both ethanol and water extracts were evaluated for phytochemical content, antioxidant potential, enzyme inhibitory activity, antimicrobial activity and photoprotective activity. LC-MS/MS profiling revealed significant regional and solvent-based variation in phenolic and flavonoid composition. Ethanol extracts had consistently higher concentrations of the major flavonoids galangin, chrysin, and naringenin, with Mosul and Sulaymaniyah samples having the most enriched profiles. GC-MS analysis also revealed a broad range of fatty acids, alkanes, and phenolic esters, with Duhok's rich content of palmitic acid and Mosul's unique organoselenium compounds. ICP-MS elemental analysis showed significant diversity in macro- and trace elements, with high concentrations of calcium, magnesium, and iron. Toxic elements such as lead were present at trace levels within acceptable safety levels. Biological tests showed that ethanol extracts possessed superior antioxidant activity, expressed as high total phenolic and flavonoid content, DPPH radical scavenging, and total antioxidant capacity. Sulaymaniyah and Duhok ethanol extracts showed the most activity. Besides, ethanol extracts exhibited significant antimicrobial activity against Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, Bacillus subtilis and Candida albicans, where Erbil and Sulaymaniyah samples were the most effective. Sun protection factor (SPF) investigation indicated that Mosul ethanol extract exhibited the highest SPF value (17.9 at 20 ppm), confirming the UV-protective activity of propolis. The study also evaluated propolis inhibitory activity on human erythrocyte Glutathione S-Transferase (GST). The most active GST inhibition was that of Sulaymaniyah ethanol extract (IC5₀ = 5.52 µg/mL), which correlated with its high content of flavonoids. The dual role of propolis as both an antioxidant and as an enzyme modulator indicates its medicinal potential as well as the need for careful use in health facilities. Overall, the findings validate Northern Iraqi propolis's chemical and biological richness, warranting its application in nutraceutical, pharmaceutical and cosmetic formulations. The study highlights the contribution of extraction protocols and geographic origin in standardizing propolis product quality and efficacy.