A New Leaf Essential Oil from Endemic Gynoxys laurifolia (Kunth) Cass. of Southern Ecuador: Chemical and Enantioselective Analyses

The fresh leaves of Gynoxys laurifolia (Kunth) Cass. (Asteraceae), collected in the province of Loja (Ecuador), were submitted to steam distillation, producing an essential oil with a yield of 0.02% by weight. This volatile fraction, described here for the first time, was submitted to qualitative (GC-MS) and quantitative (GC-FID) chemical analyses, on two orthogonal columns (non-polar and polar stationary phase). A total of 90 components, corresponding to 95.9-95.0% by weight on the non-polar and polar stationary phase, respectively, were detected and quantified with at least one column. Major constituents ( >= 3%) were: germacrene D (18.9-18.0%), (E)- beta-caryophyllene (13.2-15.0%), alpha-pinene (11.0-10.3%), beta-pinene (4.5-4.4%), fi-phellandrene (4.0-3.0%), bicyclogermacrene (4.0-3.0%), and bakkenolide A (3.2-3.4%). This essential oil was dominated by sesquiterpene hydrocarbons (about 45%), followed by monoterpene hydrocarbons (about 25-30%). This research was complemented with the enantioselective analysis of some common chiral terpenes, carried out through 2,3-diethyl-6-tert-butyldimethylsilyl-beta-cyclodextrin and 2,3-diacetyl-6tert-butyldimethylsilyl- beta-cyclodextrin as stationary phase chiral selectors. As a result, (1S,5S)-(-)beta-pinene, (R)-(-)- alpha-phellandrene, (R)-(-)- beta-phellandrene, (S)-(-)-limonene, (S)-(+)-linalyl acetate, and (S)-(-)-germacrene D were observed as enantiomerically pure compounds, whereas alpha-pinene, linalool, terpinene-4-ol, and alpha-terpineol were present as scalemic mixtures. Finally, sabinene was practically racemic. Due to plant wildness and the relatively low distillation yield, no industrial applications can be identified, in the first instance for this essential oil. The focus of the present study is therefore academic.

Automated summary

This study describes for the first time the composition and content of the essential oil of Gynoxys laurifolia (Kunth) Cass. collected in Loja province, Ecuador. The essential oil is dominated by sesquiterpene hydrocarbons (about 45%) and monoterpene hydrocarbons (about 25-30%). In addition, enantioselective analysis of some common chiral terpenes was conducted. Due to the wildness of the plant and the relatively low distillation yield, no industrial applications can be identified at this stage for this essential oil.