The Leaf Essential Oil of Gynoxys buxifolia (Kunth) Cass. (Asteraceae): A Good Source of Furanoeremophilane and Bakkenolide A

Abstract

The present study describes the chemical and enantiomeric composition of a new essential oil, distilled from the dry leaves of Gynoxys buxifolia (Kunth) Cass. The chemical analysis was conducted by GC-MS and GC-FID, on two orthogonal capillary columns. A total of 72 compounds were detected and quantified with at least one column, corresponding to about 85% by weight of the whole oil mass. Of the 72 components, 70 were identified by comparing the respective linear retention indices and mass spectra with data from the literature, whereas the two main constituents were identified by preparative purification and NMR experiments. The quantitative analysis was carried out calculating the relative response factor of each compound according to their combustion enthalpy. The major constituents of the EO (≥3%) were: furanoeremophilane (31.3–28.3%), bakkenolide A (17.6–16.3%), caryophyllene oxide (6.0–5.8%), and (E)-β-caryophyllene (4.4%). Additionally, the hydrolate was also analyzed with respect to the dissolved organic phase. About 40.7–43.4 mg/100 mL of organic compounds was detected in solution, of which p-vinylguaiacol was the main component (25.4–29.9 mg/100 mL). Finally, the enantioselective analysis of some chiral terpenes was carried out, with a capillary column based on β-cyclodextrin chiral stationary phase. In this analysis, (1S,5S)-(−)-α-pinene, (1S,5S)-(−)-β-pinene, (S)-(+)-α-phellandrene, (S)-(+)-β-phellandrene, and (S)-(−)-terpinen-4-ol were detected as enantiomerically pure, whereas (S)-(−)-sabinene showed an enantiomeric excess of 69.2%. The essential oil described in the present study is a good source of two uncommon volatile compounds: furanoeremophilane and bakkenolide A. The former lacks bioactivity information and deserves further investigation, whereas the latter is a promising selective anticancer product.

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

“…As mentioned in the introduction, the EOs of other Gynoxys spp. from the same region (G. miniphylla, G. rugulosa, and G. buxifolia) have been described in previous studies, as a part of the present project [16][17][18]. On the one hand, the volatile fraction of G. buxifolia was very different from all the others, including the one described in the present report.…”

“…Despite being the less abundant of the major components (about 3%), this oxygenated sesquiterpene is absolutely the most interesting one, at least from the phytochemical point of view. In fact, whereas α-pinene, germacrene D, and (E)-β-caryophyllene are also the main components in almost all the EOs currently under investigation in the genus Gynoxys, bakkenolide A was only found so far in G. buxifolia [18]. On that occasion, the authors reported that the two main compounds (furanoeremofilane and bakkenolide A), despite being rare in EOs, are known to be often detected together in plants, due to biosynthetic reasons.…”

“…Helium was used as the carrier gas, with a flow rate of 1 mL/min and the injector was programmed to run in SPLIT mode at 230 • C. The following thermal program was used to conduct the elution: 50 • C for 5 min, then a gradient of 2 • C/min to 100 • C, a second gradient of 3 • C/min to 150 • C, and a third gradient of 5 • C/min to 200 • C. Finally, a fourth ramp of 15 • C/min was used to raise the temperature to 230 • C, where it remained for 15 min. By comparing each linear retention index, calculated in accordance with Van den Dool and Kratz, and the associated mass spectrum with published data [18][19][20]34], the components of the EO were determined. The homologous series C9-C25 alkanes, used to calculate linear retention indices, were purchased from Sigma-Aldrich.…”

“…In Ecuador, 33 species are reported, of which 23 are endemics [15]. So far, according to the literature, only five species have been studied for their EOs, three of which (G. miniphylla, G. rugulosa, and G. buxifolia) are a part of this project [16][17][18]. The object of the present study is the EO distilled from the leaves of Gynoxys laurifolia (Kunth.)…”

Essential oils of two Great Basin composites: Chaenactis douglasii and Dieteria canescens from southwestern Idaho

“…ligustica 59.0 41.0 2.0 98.0 ------56.0 44.0 --------[43] .5 0.2 99.8 92.3 7.7 86.1 13.9 90.5 9.5 71.9 28.1 12.6 87.4 33.4 66.6 ----[15] Coreopsis triloba 18.4 81.6 100.0 0.0 2.5 97.5 --------0.6 ------71.6 28.4 --7.7 92.3 ----[50] .3 89.7 0.0 100.0 --------------[51] Gynoxys buxifolia 0.0 100.0 0.0 100.0 ------0.0 100.0 --------[52] Gynoxys miniphylla 0.9 99.1 44.1 55.9 ----------4.5 95.5 ----[53] Gynoxys rugulosa 37.1 62.9 100.0 0.0 ------57.4 42.6 49.9 50.1 95.5 4.5 ----[54] Solidago canadensis 73.9 26.1 36.4 63.6 97.7 2.3 --------72.4 27.6 ----[55] Tagetes maxima 88.3 11.7 57.6 42.4 95.6 4.4 --------------[56] …”