The in vitro evaluation of cholinesterase inhibition and the antioxidant effect of Cupressus arizonica Greene, Cupressus lusitanica Mill. and Pinus canariensis C.Sm. aerial parts

Abstract

Globally, several medicinal plants have been reported in treating Alzheimer’s disease (AD). AD is characterised by decreased acetylcholine-mediated neurotransmission, in which acetylcholinesterase inhibitors have an impact as neuron-protective. The aim is to discover a new therapeutic agent for AD from available natural sources with fewer side effects than other synthetic ones. The current work provides evidence of the preventive and therapeutic properties of three coniferous plants, Cupressus arizonica Greene (CA), Cupressus lusitanica Mill. (CL) and Pinus canariensis C.Sm. (PC). This was achieved by screening their potential in inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Additionally, the antioxidant activity was determined through three different assays; Ferric-reducing antioxidant power, radical cation-based 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and oxygen radical absorbance capacity. Phytochemical screening was performed through the determination of their total polyphenolic content (TPC) and total flavonoid content (TFC). The results proved that the best inhibition of AChE was possessed by CL and CA (IC₅₀: 199.7 ± 15.3 and 263.7 ± 17.3 μg/mL, respectively). CA showed a significantly more potent inhibition on BChE (IC₅₀: 74.3 ± 2.1 μg/mL) than CL and PC (136.3 ± 3.8, ˃500 μg/mL, respectively), in comparison to standard. The extracts showed potent activity in the antioxidant assays (107-1143 μM Trolox eq/mg sample). CA had the highest concentration of TFC, while CL had the highest concentration of TPC. This study revealed significant in vitro antioxidant potential, and AChE and BChE inhibitory effects of CA. In conclusion, CA extract could be a promising source of bioactive metabolites for treating neurological diseases.