Variability in bioactive compounds, antioxidant activity, and cytotoxicity assessment of diverse organs of Iranian oak (Quercus brantii Lindl.)

The genus Quercus with over 1000 species is extensively dispersed throughout the temperate woodlands of the Northern Hemisphere and tropical climate zones. Numerous physiological functions, such as antibacterial, anti-inflammatory, liver-protective, gastroprotective, anticancer, antidiabetic, and antioxidant activities, have been documented and associated with the occurrence of bioactive compounds like phenolic acids, triterpenoids, and plant-based polyphenolic compounds. Given that different plant organs differ in terms of secondary metabolite production, this aim was to investigate the diversity of phytochemical compounds, antioxidant activity, and cytotoxicity of different parts of oak and its by-products. Total phenolic content varied between 50.4 to 125.3 mg GAE/g DW, with the maximum and minimum being in the gall and leaf. Fruit had the highest (68.3 mg RE/g DW) and the lowest (13.5) total flavonoid content in the gaz alafi. The highest (74.9 mg GAE/g DW) and minimum (8.9 mg GAE/g DW) total tannin were observed in the gall and gaz alafi, respectively. Gallic acid, salicylic acid, rosmarinic acid, 2,5-dihydroxybenzoic acid, chlorogenic acid, rutin, quercetin, caffeic acid, p-coumaric acid, and kaempferol were identified as the main phenolic compounds by HPLC-PDA analysis. Based on the results of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, no significant cytotoxicity was observed on normal cell line (HDF) and gastric cancer cells (MKN45). This study shows that different parts of oak and its by-products can be valuable sources of bioactive compounds and can be used in various therapeutic and industrial applications.