Centaurea karduchorum Boiss. from Eastern Anatolia: Phenolic composition, antioxidant and enzyme inhibitory activities

The phenolic composition of lyophilized hydrophilic extracts obtained from root, stem, leaf and flower of Centaurea karduchorum Boiss. a medicinal plant endemic to Eastern Anatolia (Turkey) used as anti-diabetic agent was characterized for the first time. Liquid chromatography mass spectrometry (LC/MS) analysis revealed that luteolin derivatives and chlorogenic acid were the dominating compounds contributing, respectively, from 16.1% (root) to 33.7% (stem) and from 7.3% (flower) to 12.0% (root) of total phenolics. Total reducing capacities of the extracts varied from 24.1 (root) to 38.5 (flower) mg gallic acid Eq./g DW [Folin-Ciocalteu assay] and from 274.0 (root) to 441.0 (stem) μmol Fe2+/g DW [FRAP assay]. The oxygen radical absorbance capacity (ORAC assay) values varied from 930.5 (root) to 1853.5 (stem) μmol trolox Eq./g DW. The leaf extract exhibited a pronounced inhibitory activity towards α-glucosidase (IC50: 0.63 ± 0.00 mg/ml) and a weak inhibitory activity towards amylase (IC50: 14.63 ± 0.67 mg/ml), which suggests a potential to reduce postprandial hyperglycaemia and supports its traditional use as antidiabetic agent.