Phenolic profile, antioxidant and enzyme inhibitory potential of Onosma tauricum var. tauricum

This study focused on phytochemical characterization and biological evaluation, both antioxidant and enzymatic inhibition, of ethyl acetate (OTT-EtOAc), methanol (OTT-MeOH), and water (OTT-W) extracts from Onosma tauricum var. tauricum aerial parts. The OTT-W extract was found to be the richest one in terms of its phenolic and flavonoid contents. Amounts of the phenolic and flavonoid compounds were determined as 40.88 μmol GAEs/g and 7.40 μmol REs/g dry plant (dp), respectively. The OTT-MeOH and OTT-W extracts were also found to contain significant amounts of chlorogenic acid, rosmarinic acid, p-hydroxybenzoic acid, caffeic acid, rutin, p-coumaric acid, trans-cinnamic acid, luteolin, and apigenin. The OTT-W extract showed remarkable antioxidant activity in phosphomolybdenum, ferrous ion chelating, reducing power, and radical scavenging assays. The OTT-MeOH extract exhibited inhibitory activity on acetylcholinesterase (AChE) (54.62 μmol GALAEs/g dp), while the extracts remained almost inactive on butyrylcholinesterase (BChE). The OTT-W extract also exhibited inhibitory activity on tyrosinase (90.66 μmol KAEs/g dp) and α-glucosidase (2258.87 μmol ACEs/g dp). The results suggest that especially the OTT-MeOH and OTT-W extracts can be used as a source of alternative natural products in the treatment of diseases caused by the enzymes evaluated here.