A New Essential Oil from the Leaves of Gynoxys rugulosa Muschl. (Asteraceae) Growing in Southern Ecuador: Chemical and Enantioselective Analyses

An essential oil, distilled from the leaves of the Andean species Gynoxys rugulosa Muschl., is described in the present study for the first time. The chemical composition was qualitatively and quantitatively determined by GC-MS and GC-FID, respectively. On the one hand, the qualitative composition was obtained by comparing the mass spectrum and the linear retention index of each component with data from literature. On the other hand, the quantitative composition was determined by calculating the relative response factor of each constituent, according to its combustion enthalpy. Both analyses were carried out with two orthogonal columns of nonpolar and polar stationary phases. A total of 112 compounds were detected and quantified with at least one column, corresponding to 87.3-93.0% of the whole oil mass. Among the 112 detected components, 103 were identified. The main constituents were alpha-pinene (5.3-6.0%), (E)-beta-caryophyllene (2.4-2.8%), alpha-humulene (3.0-3.2%), germacrene D (4.9-6.5%), delta-cadinene (2.2-2.3%), caryophyllene oxide (1.6-2.2%), alpha-cadinol (3.8-4.4%), 1-nonadecanol (1.7-1.9%), 1-eicosanol (0.9-1.2%), n-tricosane (3.3-3.4%), 1-heneicosanol (4.5-5.8%), n-pentacosane (5.8-7.1%), 1-tricosanol (4.0-4.5%), and n-heptacosane (3.0-3.5%). Furthermore, an enantioselective analysis was carried out on the essential oil, by means of two cyclodextrin-based capillary columns. The enantiomers of alpha-pinene, beta-pinene, sabinene, alpha-phellandrene, beta-phellandrene, linalool, alpha-copaene, terpinen-4-ol, alpha-terpineol, and germacrene D were detected, and the respective enantiomeric excess was calculated.

Automated summary

This study describes the first-ever report of an essential oil obtained by distilling the leaves of the Andean species Gynoxys rugulosa Muschl. The chemical composition of the essential oil was determined qualitatively and quantitatively using GC-MS and GC-FID. A total of 112 compounds were identified and quantified, accounting for 87.3-93.0% of the total oil mass. The main constituents were alpha-pinene, (E)-beta-caryophyllene, alpha-humulene, germacrene D, delta-cadinene, caryophyllene oxide, alpha-cadinol, 1-nonadecanol, 1-eicosanol, n-tricosane, 1-heneicosanol, n-pentacosane, 1-tricosanol, and n-heptacosane. Enantioselective analysis of the essential oil revealed the presence of enantiomers for several compounds.