Chemical, Enantioselective, and Sensory Analysis of a Cholinesterase Inhibitor Essential Oil from Coreopsis triloba S.F. Blake (Asteraceae)

The fresh leaves of Coreopsis triloba S.F. Blake, collected at Cerro Villonaco in Loja, Ecuador, were investigated with respect to their essential oil (EO). The chemical composition was determined qualitatively through gas chromatography coupled with mass spectrometry (GC-MS) and quantitatively by gas chromatography coupled with flame ionization (GC-FID), using relative response factors (RRF) based on the enthalpy of combustion. The essential oil contained between 92.5% and 93.4% of monoterpene hydrocarbons, with (E)-beta-ocimene being the main component (35.2-35.9%), followed by beta-phellandrene (24.6-25.0%), alpha-pinene (15.3-15.9%), myrcene (10.9-11.0%), sabinene (2.2-2.4%), (Z)-beta-ocimene (1.5%), and germacrene D (1.2-1.3%). The enantiomeric distribution of alpha-pinene, beta-pinene, limonene, and germacrene D was also determined. The main components responsible for the aroma were identified through aroma extract dilution analysis (AEDA), a gas chromatography-olfactometry (GC-O) based technique, being alpha-pinene, beta-pinene (0.6%), terpinolene (0.1%), alpha-copaene (0.1-0.3%), beta-phellandrene, and (E)-4,8-dimethyl-1,3,7-nonatriene (0.1-0.2%) the main olfactory constituents according to the decreasing factor of dilution (FD) order. The biological tests showed IC50 inhibition values of 42.2 and 6.8 mu g/mL for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively.