Cousinia birandiana (Asteraceae): phytochemical composition, antioxidant and enzyme inhibition capacity

Cousinia birandiana is one of the widely spread species of the Asteraceae family. In this study, the total phenolic and flavonoid contents, the inhibitory effect on α-amylase, α-glucosidase, acetylcholinesterase and butyrylcholinesterase enzymes, the antioxidant capacity (by DPPH, ABTS, FRAP, CUPRAC tests) and the phytochemical content (by LC-HRMS) of the ethanol extract and fractions were studied. As a result, it was shown that ethanol extract has better enzyme inhibitory effects on α-amylase, AChE and BChE enzymes with 300.000, 380.605 and 133.567 μg/mL IC₅₀ values. Besides that, the highest phenolic and flavonoid content was found in the ethyl acetate fraction (735.986 mg_GAE/g_extract and 952.317 mg_CA/g_extract, respectively). It is observed that the same fraction has better antioxidant activity in DPPH (IC₅₀ =112.701 mg/mL), ABTS (9.494 μM _Trolox/g_extract) and CUPRAC (1120.454 mg_GAE/g_extract) tests and the n-hexane fraction has a higher FRAP (1351.199 mmol Fe²⁺/g_extract) antioxidant effect. According to the phytochemical analyses quinic acid, chlorogenic acid and isoquercitrin were found as major compounds in the ethanol extract and fractions. In addition, the same assays were carried out with these major substances. So, this plant can be viewed as a promising bio-resource for pharmaceuticals and biomedical products.