A New Essential Oil from the Leaves of the Endemic Andean Species Gynoxys miniphylla Cuatrec. (Asteraceae): Chemical and Enantioselective Analyses

Abstract

A previously uninvestigated essential oil (EO) was distilled from Gynoxys miniphylla Cuatrec. (Asteraceae) and submitted to chemical and enantioselective analyses. The qualitative and quantitative analyses were conducted by GC-MS and GC-FID, over two orthogonal columns (5%-phenyl-methylpolysiloxane and polyethylene glycol stationary phases). Major constituents (≥2%) were, on both columns, respectively, as follows: α-phellandrene (16.1–17.2%), α-pinene (14.0– 15.0%), germacrene D (13.3–14.8%), trans-myrtanol acetate (8.80%), δ-cadinene (4.2–4.6%), β-phellandrene (3.3–2.8%), (E)-β-caryophyllene (3.1–2.0%), o-cymene (2.4%), α-cadinol (2.3–2.6%), and α-humulene (1.7–2.0%). All the quantified compounds corresponded to 93.5–97.3% by weight of the whole essential oil, with monoterpenes counting for 53.8–55.6% of the total, and sesquiterpenes for 38.5–41.4%. For what concerns the enantioselective analyses, the chiral components were investigated through a β-cyclodextrin-based enantioselective column (2,3-diethyl-6-tert-butyldimethylsi-lyl-β-cyclodextrin). A total of six chiral metabolites were analysed and the respective enantiomeric excess calculated as follows: (1S,5S)-(−)-α-pinene (98.2%), (1S,5S)-(−)-β-pinene (11.9%), (1R,5R)-(+)-sabinene (14.0%), (R)-(−)-α-phellandrene (100.0%), (R)-(−)-β-phellandrene (100.0%), and (S)-(−)-ger-macrene D (95.5%). According to the chemical composition and enantiomeric distribution of major compounds, this EO can be considered promising as a cholinergic, antiviral and, probably, analgesic product.