A phytochemical study on Onosma demirizii

Onosma species have traditionally been used as laxative and anthelmintic agents as well as their uses in eye, blood diseases, bronchitis, abdominal pain, strangury, thirst, itch, leucoderma, fever, wounds, burns, piles, and urinary calculi. The aim of this study is to determine the antioxidant and enzyme inhibitory activities of ethyl acetate, methanol, and water extracts obtained from Onosma demirizii, as well as their chemical composition by using liquid chromatography–electrospray tandem mass spectrometry (LC–ESI–MS/MS). Antioxidant capacity was tested by using different chemical methods including radical scavenging, reductive effect, phosphomolybdenum and metal chelating assays. Enzyme inhibitory effect was investigated against cholinesterase, tyrosinase, α-amylase and α-glucosidase. As a result of the LC–ESI–MS/MS analyses, hesperidin, hyperoside, chlorogenic acid, rosmarinic acid, and pinoresinol were found to be the major compounds of the extracts, especially the MeOH extract. Except for the ferrous ion chelating effect, the methanol extract showed remarkable antioxidant activity in phosphomolybdenum, radical scavenging on DPPH and ABTS, and reducing power (CUPRAC and FRAP) assays. Ethyl acetate extract, excluding tyrosinase enzyme, exhibited the highest inhibitory activity on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-glucosidase and α-amylase. In addition, Based on the correlation coefficients calculated separately for all experimental parameter pairs, major phytochemicals were found to be highly in correlation with the antioxidant and enzyme inhibitory activities of the extracts. The results indicate that O. demirizii extracts could be used as a source of new and alternative antioxidant and enzyme inhibitory agents. Keywords: Onosma demirizii, Chemical composition, Antioxidant activity, Enzyme inhibitory activity.