Essential Oil and Crude Extracts of Pulicaria arabica (L.) Cass. Aerial Parts: Chemical Composition, Antioxidant Effect, α-Glucosidase, Acetylcholinesterase, and Butyrylcholinesterase Inhibitory Activities

Abstract

Plants have been an important source of bioactive compounds since ancient times and have recently attracted much attention from researchers and consumers due to the toxic effects of synthetic drugs. Our work aimed to study the chemical composition and some biological activities of the essential oil (EO) and the crude extracts of an endemic plant from Algeria: Pulicaria arabica (L.) Cass. Gas chromatographymass spectrometry (GC/MS) analysis of the EO is conducted for the identification of eight compounds representing 99.6% of the total content. The main compounds were α-Cadinol (35.0%), δ-Cadinene (22.5%), τ-Muurolol (12.6%), and τ-Cadinol (11.7%). The highest contents of total phenolics and flavonoids of the crude extracts were recorded with the methanol extract (185.91 ± 3.11 μg GAE/mg and 62.86 ± 1.98 μg QE/mg of extract, respectively). The antioxidant activity of the EO and the crude extracts was evaluated using six different methods: DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity, ABTS (2,2’-azinobis(3-ethylbenzothiazoline)-6-sulfonic)) scavenging activity, the ferric reducing ability of plasma (FRAP), iron chelation, β-carotene bleaching inhibition, and cupric reducing antioxidant capacity (CUPRAC). Acetone and methanol extracts exhibited the highest antioxidant capacity, which can be attributed to their high phenol content. On the contrary, the EO and the hydro-methanolic extract exhibited the highest α-glucosidase inhibitory activity (IC50: 39.74 ± 1.91 and 42.45 ± 4.67 μg/mL, respectively). All the tested extracts were found to be inactive against acetylcholinesterase (AChE) while they showed an interesting inhibitory effect against butyrylcholinesterase (BChE). These findings showed that Pulicaria arabica EO and extracts have important biological activities and might be used in the treatment of diabetes and Alzheimer's disease with antioxidant properties.