Elettaria cardamomum (L.) Maton essential oil as potential acetylcholinesterase and butyrylcholinesterase inhibitor: A bioguided fractionation approach

Objective: Elettaria cardamomum (L.) Maton is a plant of the Zingiberaceae family and has been used for centuries in traditional Ayurvedic and Chinese medicine for a variety of different purposes, as infusions, decoctions, distillates and essential oils, which we have focused on. The rapid spread of the use of the essential oil of this plant throughout the world and its use in food, medicine, and fragrance fields makes it a very interesting matrix in the research for specialized bioactive metabolites. Essential oils have traditionally been used to improve cognitive abilities and alleviate other symptoms associated with Alzheimer’s disease (AD) Inhibitors of cholinesterase enzymes are currently used as drugs in AD treatment (e.g., galantamine, rivastigmine, donepezil). Therefore, the aim of this study was to investigate the possible inhibitory activity of E. cardamomum essential oil towards acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and finally to find the compounds to which this activity could potentially be attributed using abio-guided fractionation approach. Methods: Whole cardamom fruits (opened capsules and seeds) and, separately, seeds and fruits were hydrodistilled in a Clevenger apparatus for 4 hours. In addition, five batches of cardamom essential oil (supplied by Witt Italia) were investigated. All essential oil samples were subjected to an AChE and BChE in vitro colorimetric assay by the Ellman method. Fractionation was performed using a PuriFlash 450 column chromatography (Sepachrom, Italy), equipped with both a UV and Evaporative Light Scattering detector (ELSD). Petroleum ether and ethylacetate were used as mobile phase solvents; Sphera 50 µm silica cartridges (Sepachrom, Italy) were selected. The eluent flow was maintained at 25 ml/min and the volume of essential oil injected was 1 ml. Chemical characterization of the solutions of the essential oils and their respective fractions performed by GC-MS analysis. Results: Cardamom essential oil was found to be active in inhibiting both cholinesterase enzymes. Bio-guided fractionation approach allowed us to isolate fractions/pure compounds that can be individually tested to evaluate their activity. The hydrocarbon fraction of cardamom essential oil was found to be inactive towards both AChE and BChE. The oxygenated fraction, on the other hand, was active towards both enzymes. Terpinyl acetate and 1,8-cineole were found to be the responsible of the inhibitory activity. Conclusions: Cardamom essential oil was found to be active towards both cholinesterase enzymes, thus resulting very promising for further in-depth studies looking for complementary treatment to conventional therapy.