Context: Due to the interesting potential of essential oils (EO) against cholinesterases and their close relation in Alzheimer's disease, the EO of Lepechinia betonicifolia (Lam) Epling (Lamiaceae), a native shrub from Ecuador, was assessed. Chemical profiling and enantiomeric distribution were also recorded for the first time.
Objective: To analyse the chemical profile including the enantiomeric composition and anticholinesterase effect exerted by EO of L. betonicifolia.
Materials and methods: The EO of L. betonicifolia fresh aerial parts was obtained by hydrodistillation in a Clevenger-type apparatus. Physical properties were determined according to standard norms. The chemical composition was determined by GC-MS and GC-FID. Enantioselective GC-MS analysis was carried out by using a capillary chiral column. Anticholinesterase effect was assessed by Ellman's method with acetylthiocoline as substrate and Ellman's reagent (DTNB) to detect its hydrolysis at 405 nm for 60 min. Donepezil was used as a reference drug. EO was dissolved in methanol to reach 10 mg/mL concentration and two more 10× dilutions were included.
Results: Thirty-nine constituents were identified corresponding to 97.55% of the total oil composition. The main components were β-pinene (30.45%), sabinene (27.98%), α-pinene (4.97%), β-phellandrene (4.79%), E-caryophyllene (4.44%) and limonene (3.84%). L. betonicifolia EO exerted a strong inhibitory effect over the AChE enzyme with an IC50 value of 74.97 ± 1.17 μg/mL.
Discussion and conclusions: Current chemical characterisation and anticholinesterase effect of EO of L. betonicifolia encourage us to propose this EO as a candidate for the preparation of functional foods or as adjuvant therapy for Alzheimer's disease.
Keywords: Enantiomeric distribution; acetylcholinesterase; chemical profiling; pinene; sabinene.