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

Abstract

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)-β-caryophyllene (13.2–15.0%), α-pinene (11.0–10.3%), β-pinene (4.5–4.4%), β-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-β-cyclodextrin and 2,3-diacetyl-6-tert-butyldimethylsilyl-β-cyclodextrin as stationary phase chiral selectors. As a result, (1S,5S)-(−)-β-pinene, (R)-(−)-α-phellandrene, (R)-(−)-β-phellandrene, (S)-(−)-limonene, (S)-(+)-linalyl acetate, and (S)-(−)-germacrene D were observed as enantiomerically pure compounds, whereas α-pinene, linalool, terpinene-4-ol, and α-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.

New Essential Oils from Ecuadorian Gynoxys cuicochensis Cuatrec. and Gynoxys sancti-antonii Cuatrec. Chemical Compositions and Enantioselective Analyses

“…All the other analyzed chiral compounds were present as scalemic mixtures in both EOs. Unlike the chemical compositions, the enantiomeric distributions of all the known Gynoxys EOs did not apparently present a common pattern. − The detailed results of the enantioselective analyses on G. sancti-antonii and G.…”

“…Furthermore, a series of heavy aliphatic compounds (mainly long-chained aldehydes, alkenes, and alkanes) was a characteristic pattern in the final part of many GC profiles. 10,11,13 Finally, a special consideration must be given to G. buxifolia 2, where two chiral selectors (2,3-diacetyl-6-tert-butyldimethylsilyl-β-cyclodextrin and 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin) were used in order to ensure the best enantiomeric separations. As usual, the variable enantiomeric distribution of the same chiral metabolites, within a botanical genus or even the same species, is the result of different biological functions and properties, that two optical isomers can exert in a living organism.…”

“…sancti-antonii. Furthermore, a series of heavy aliphatic compounds (mainly long-chained aldehydes, alkenes, and alkanes) was a characteristic pattern in the final part of many GC profiles. ,, Finally, a special consideration must be given to G. buxifolia EO, whose chemical composition was completely different from all the other species, the major compounds being the very rare furanoeremophilane and bakkenolide A …”

“…So far, the EOs obtained from Gynoxys miniphylla Cuatrec., Gynoxys rugulosa Muschl., Gynoxys buxifolia (Kunth) Cass., and Gynoxys laurifolia (Kunth) Cass. have already been studied and published. − The composition of Gynoxys szyszylowiczii Hieron. volatile fraction is ready to be published, whereas Gynoxys calyculisolvens Hieron., Gynoxys pulchella (Kunth) Cass., Gynoxys reinaldii Cuatrec., Gynoxys hallii Hieron., and Gynoxys azuayensis Cuatrec.…”

Chemical and Enantioselective Analyses of an Unprecedented Essential Oil from Ecuadorian Aiouea montana: A Natural Source of S-Methyl-O-2-phenylethyl Carbonothioate

“…Furthermore, the climatic change and the unwise exploitation of natural resources make the awareness about biodiversity an urgent need. Therefore, with the aim of contributing to the discovery of new natural products, our group has been studying the phytochemistry of the Ecuadorian biodiversity for more than 20 years. , In the past few years, our interest was focused on the description of new essential oils (EOs), with emphasis on their chemical and enantiomeric compositions, mainly from a biochemical point of view. − The present investigation was conducted in the same context, and it raised from the evidence that the leaves of Aiouea montana (Sw.) R. Rohde emitted a strong sulfurous odor all year long, suggesting the presence of uncommon volatile metabolites in high amounts. Furthermore, no bibliographical information was found in this respect, opening the way to possibly interesting results.…”