Phytochemical variation, phenolic compounds and antioxidant activity of wild populations of Iranian oak.

The genus Quercus with over 1,000 species, is extensively dispersed throughout the temperate woodlands of the Northern Hemisphere and tropical climate zones. The Quercus genus is rich in phenolic acids, triterpenoids, and plant-based polyphenolic compounds. It also has numerous biological effects, such as antibacterial, anti-inflammatory, liver-protective, gastroprotective, anticancer, antidiabetic, and antioxidant activities. To investigate the morphological and phytochemical diversity of Iranian oak (Quercus brantii Lindl.) populations from ten different geographic regions in Iran were collected. Morphological, phytochemical and cytotoxic traits were measured and analyzed. Among morphological and phytochemical traits, dry leaf weight (69.21%) had the maximum coefficient of variation. In addition, the highest total phenol (100.17 mg GAE/g DW), total flavonoid content (74.6 mg RE/g DW), and total tannin (56.60 mg GAE/g DW) were found in the Sardasht population, with the minimum in the Piranshahr population. The IC(50) values of the populations ranged from 5.52 to 18.65 µg/mL, with the lowest in the Sardasht population and the most elevated in the Ilam population. Gallic acid, salicylic acid, rutin, and rosmarinic acid were identified as the principal phenolic compounds. Cluster analysis of populations based on morphological and phytochemical data represented 3 main groups. Principal component analysis revealed that the first and second components explained 38.52% and 30.01% of the total variance, respectively. Oak fruit extracts were not cytotoxic at concentration of 100 µM. Based on the results of this study, the best oak population can be selected to achieve the highest yield, total phenolic content, total flavonoid content, and total tannin content, according to the needs of the pharmaceutical and food industries.