Evaluation of the antioxidant and acetylcholinesteraseinhibitory activities of Arnebia densiflora Ledeb.

Arnebia densiflora Ledeb. (Boraginaceae), a medicinal plant growing in Turkey, has been reported to contain a well-known red pigment, shikonin, a naphthoquinone derivative. In the current study, the acetylcholinesterase (AChE) inhibitory and antioxidant activities of the chloroform, ethyl acetate, methanol, and water extracts of the root, stem, and flowers of the plant, as well as shikonin, were investigated. AChE inhibition was tested using an ELISA microplate reader at 250, 500, 1000, and 2000 μg mL^-1. Antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test and the Fe^+2-ferrozine test system for metal chelating power. The results indicated that the methanol and water extracts of the roots had a moderate DPPH radical scavenging effect at 2000 μg mL^-1, while the extracts exerted a better ferrous ion chelating effect as compared to the reference, butylated hydroxyanisole. Only the root chloroform extract showed mild inhibition against AChE at 62.5 μg mL^-1 (49.6 ± 1.69%). Shikonin was inactive in all of the assays performed.