Biological evaluation of Cetrarioid clade as cholinesterase inhibitors

OBJECTIVE: Deficiencies in the neurotransmitter acetylcholine have been linked to the pathogenesis of Alzheimer's disease (AD). Therefore, cholinesterase inhibitors are potentially clinical effective for the symptomatic treatment of AD. Little is known about the neuroprotective activity of lichens as cholinesterase inhibitors. The aim of the present work is to evaluate for the first time the activity of five methanol extracts of lichens from Cetraroid clade: Cetraria commixta (Nyl.) Th.Fr, Cetraria crespoae (Barreno & Vazquez) Karnefelt, Cetraria cucullata (Bell.) Ach., Cetraria ericetorum. Opiz, Cetraria nivalis (L.) Ach and Asahinea scholanderi (Llano) as acetylcholinesterase (AchE) and butyrilcholinesterase (BchE) inhibitors.

METHODS: The AChE and BuChE activities were evaluated using the Ellman’s method at 25, 50 and 100 µg/ml methanol extract concentrations. Chemical analysis was performed using High Performance Liquid Chromatography (HPLC-UV).

RESULTS: Among all lichen extracts, Asahinea scholanderi was found the most potent AchE inhibitor (IC₅₀ = 0.11 ± 0.006) followed by Cetraria nivalis (IC₅₀ = 0.16 ± 0.013), Cetraria cucullata (IC₅₀ = 0.18 ± 0.014). Regarding the action on BchE, Asahinea scholanderi was once again the most active lichen specie (IC₅₀= 0.29 ± 0,004) followed by Cetraria cucullata (IC₅₀= 0.31 ± 0,001) and Cetraria commixta (IC₅₀= 0.49 ± 0,018). Since Asahinea scholanderi was the most active cholinesterase inhibitor, phytochemical analysis was performed. HPLC analysis of methanol extract revealed that the main compounds were α- and β-alectoronic, β-collatolic and usnic acid.

CONCLUSION: Our findings suggest that Asahinea scholanderi methanol extract display inhibitory activities against both AChE and BuChE, being a useful promising agent for AD treatment.