Chemical Profiling of Drimys granadensis (Winteraceae) Essential Oil, and Their Antimicrobial, Antioxidant, and Anticholinesterase Properties.

Abstract

A complete and comprehensive chemical and biological study of Drimys granadensis, a native Ecuadorian aromatic plant, was conducted. By conventional steam distillation from dried leaves, a yellowish, translucent essential oil (EO) with a density of 0.95 and a refractive index of 1.5090 was obtained. The EO was analyzed by gas chromatography coupled to a mass spectrometer (GC/MS) and an FID detector (GC/FID), respectively. Enantiomeric distribution was also carried out by GC/MS using a chiral selective column (diethyl tert-butylsilyl-BETA-cyclodextrin). The microdilution broth method was employed to assess the antibacterial and antifungal activity of the EO against a panel of opportunistic microorganisms. Antioxidant capacity was measured using diphenyl picryl hydrazyl (DPPH) and azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals. Finally, the inhibitory potential of the EO against acetylcholinesterase was also valued. Sixty-four chemical compounds, constituting 93.27% of the total composition, were identified, with major components including γ-muurolene (10.63%), spathulenol (10.13%), sabinene (5.52%), and δ-cadinene (4.22%). The characteristic taxonomic marker of the Drimys genus, Drimenol, was detected at very low percentages (<2%). Two pairs of enantiomers ((1S,5R)-(+)-α-pinene/(1S,5S)-(-)-α-pinene; (1S,5R)-(+)-β-pinene/(1S,5S)-(-)-β-pinene) and one pure enantiomer (1R,4S)-(-)-camphene were identified. Regarding antimicrobial potency, the EO exhibited a significant moderate effect on Listeria monocytogenes with a minimal inhibitory concentration (MIC) value of 250 µg/mL, while with the remaining microorganisms, it exerted less potency, ranging from 500 to 2000 µg/mL. The EO displayed moderate effects against the ABTS radical with a half scavenging capacity of 210.48 µg/mL and no effect against the DPPH radical. The most notable effect was noticed for acetylcholinesterase, with a half inhibition concentration (IC50) of 63.88 ± 1.03 µg/mL. These antiradical and anticholinesterase effects hint at potential pharmacological applications in Alzheimer's disease treatment, although the presence of safrole, albeit in low content (ca. 2%), could limit this opportunity. Further in vivo studies are necessary to fully understand their potential applications.