A new essential oil from the native Ecuadorian species Steiractinia sodiroi (Hieron.) S.F. Blake (Asteraceae): chemical and enantioselective analyses

In the present study, the essential oil from dry leaves of Steiractinia sodiroi (Hieron.) S.F. Blake is described for the first time. The plant material, collected in the Province of Loja (Ecuador), was analytically steam-distilled in a Marcusson-type apparatus, affording an essential oil with a 0.2 ± 0.12% yield. The volatile fraction was submitted to GC–MS and GC–FID analyses, on two stationary phases of different polarity. A total of sixty-seven compounds, corresponding to 95.6–91.2% by weight of the whole oil mass, on the two columns respectively, were detected and quantified with at least one column. The quantification was carried out calculating the relative response factors of each constituent according to their combustion enthalpy. The major components were limonene (25.6–24.9%), sabinene (11.7–12.4%), germacrene D (7.7–7.0%), α-pinene (7.8–6.9%), δ-cadinene (7.3–7.0%), (E)-β-caryophyllene (4.8–4.5%), and bicyclogermacrene (3.6–3.0%). The chemical composition was complemented with the enantioselective analysis of some major chiral compounds, conducted by means of two β-cyclodextrin-based capillary columns. Three constituents, (S)-(+)-α-phellandrene, (R)-(−)-1-octen-3-ol, and (S)-(−)-limonene were enantiomerically pure, whereas (1R,5R)-(+)-β-pinene, (1S,5S)-(−)-sabinene, (R)-(−)-terpinen-4-ol, (R)-(+)-α-terpineol, and (R)-(+)-germacrene D presented an enantiomeric excess. Finally, α-pinene was present as a racemic mixture.