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

Fresh and dry leaves of Aiouea montana (Sw.) R. Rohde (Lauraceae) produced, in a quite high yield (0.88% and 1.60%, respectively), an unpleasantly smelling essential oil. The chemical composition was described in this study for the first time, detecting and quantifying 48 compounds. Major components of fresh and dry leaf essential oils were α-pinene (6.7-10.3%), ß-pinene (2.8-3.8%), α-phellandrene (12.6-14.5%), α-copaene (3.1-15.7%), δ-cadinene (0.9-3.3%), and S-methyl-O-2-phenylethyl carbonothioate (58.5-33.3%). The dominant compound was already known in the literature by synthesis; however, it was unprecedented so far in nature. The carbonothioate was identified after purification and structure elucidation, by means of mass spectrometry, NMR spectroscopy, and FTIR spectrophotometry. The spectral results were identical to all data reported in the literature for the same molecule. Furthermore, the enantioselective analysis of the essential oil was conducted on a ß-cyclodextrin-based stationary phase. Two chiral constituents, (+)-ß-phellandrene and (1R,2S,6S,7S,8S)-(-)-α-copaene, were enantiomerically pure, whereas α-thujene, camphene, ß-pinene, α-phellandrene, limonene, linalool, and germacrene D were scalemic mixtures. The different chemical and enantiomeric compositions suggested that enzymatic transformations could occur while drying.

Chemical and Enantioselective Analysis of the Essential Oils from Different Morphological Structures of Ocotea quixos (Lam.) Kosterm.

The traditional Ecuadorian spice Ishpingo, characterized by a strong cinnamon-like aroma, is constituted by the dry cupules of Amazonian species Ocotea quixos. Nevertheless, bark and leaves also present aromatic properties and are sometimes used as substitutes. In the present study, the essential oils, distilled from these morphological structures, are comparatively analyzed for their chemical and enantiomeric compositions. A total of 88 components were identified with 2 orthogonal GC columns, whereas 79, corresponding to more than 94%, were also quantified with at least 1 column. Major compounds were (E)-methyl cinnamate in cupules (35.9-34.2%), (E)-cinnamaldehyde in bark (44.7-47.0%), and (E)-cinnamyl acetate (46.0-50.4%) in leaves. For what concerns the enantioselective analysis, 10 chiral terpenes and terpenoids were detected, of which 6 were present as enantiomeric pairs in at least 1 essential oil, the others being enantiomerically pure. Both quantitative and enantioselective analyses were submitted to Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), where their results confirmed significative difference among the three products.

The Flower Essential Oil of Dalea mutisii Kunth (Fabaceae) from Ecuador: Chemical, Enantioselective, and Olfactometric Analyses.

An essential oil was distilled with 0.25% yield from fresh flowers of Dalea mutisii Kunth, a native species mainly growing in the Andean region of Ecuador. A total of 50 compounds were identified, and most of them were quantified. The chemical composition was characterized by the prevalence of monoterpene hydrocarbons (>90%). Major components were α-pinene (42.9%), ß-pinene (15.1%), ß-phellandrene (12.6%), myrcene (6.7%), and (Z)-ß-ocimene (5.4%). The essential oil was then submitted to enantioselective analysis, with a 2,3-diethyl-6-tert-butyldimethylsilyl-ß-cyclodextrin-based capillary column. An enantiomeric excess was measured for (1R,5R)-(+)-α-pinene (91.6%), (1R,5R)-(+)-ß-pinene (15.2%), (R)-(-)-α-phellandrene (4.8%), and (R)-(-)-ß-phellandrene (88.8%), whereas (R)-(+)-limonene was enantiomerically pure. A gas chromatography-olfactometry (GC-O) analysis was additionally carried out on this pleasantly fragrant essential oil, following an aroma extract dilution analysis (AEDA) approach. Main odorants were α-pinene, ß-pinene, α-phellandrene, and (Z)-ß-ocimene, with dilution factors (FD) of 8, 4, 2, and 2, respectively.

Chemical Composition, Enantiomeric Distribution, and Sensory Evaluation of the Essential Oils Distilled from the Ecuadorian Species Myrcianthes myrsinoides (Kunth) Grifo and Myrcia mollis (Kunth) DC. (Myrtaceae).

The essential oils of Myrcianthes myrsinoides and Myrcia mollis, belonging to the Myrtaceae family, were obtained by steam distillation. They were analyzed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-flame ionization detector (GC-FID), enantioselective gas chromatography, and gas chromatography-olfactometry (GC-O). A total of 58 compounds for Myrcianthes myrsinoides essential oil (EO) and 22 compounds for Myrcia mollis EO were identified and quantified by GC-MS with apolar and polar columns (including undetermined components). Major compounds (>5.0%) were limonene (5.3%-5.2%), 1,8-cineole (10.4%-11.6%), (Z)-caryophyllene (16.6%-16.8%), trans-calamenene (15.9%-14.6%), and spathulenol (6.2%-6.5%). The enantiomeric excess of eight chiral constituents was determined, being (+)-limonene and (+)-germacrene D enantiomerically pure. Eight components were identified as determinant in the aromatic profile: α-pinene, ß-pinene, (+)-limonene, γ-terpinene, terpinolene, linalool, ß-elemene and spathulenol. For M. mollis, the major compounds (>5.0%) were α-pinene (29.2%-27.7%), ß-pinene (31.3%-30.0%), myrcene (5.0%-5.2%), 1,8-cineole (8.5%-8.7%), and linalool (7.7%-8.2%). The enantiomeric excess of five chiral constituents was determined, with (S)-α-pinene and (+)-germacrene D enantiomerically pure. The metabolites ß-pinene, 1,8-cineole, γ-terpinene, terpinolene, linalool, and (E)-ß-caryophyllene were mainly responsible for the aroma of the EO. Finally, the M. myrsinoides essential oil has an inhibitory activity for cholinesterase enzymes (IC50 of 78.6 µg/ml and 18.4 µg/ml vs. acethylcholinesterase (AChE) and butyrylcholinesterase (BChE) respectively). This activity is of interest to treat Alzheimer's disease.

Phytochemistry of Three Ecuadorian Lamiaceae: Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling.

In this research, the leaves of Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling have been collected in order to perform a phytochemical study. The first species was distilled to obtain a novel essential oil (EO), while the others were submitted to ethyl acetate extraction and secondary metabolite isolation. The chemical composition of the EO from L. heteromorpha has been investigated by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography with Retention Indices (GC(RI)), identifying 25 constituents. A major compound, (-)-ledol (21.2%), and a minor compound, (-)-caryophyllene oxide (1.0%), were isolated from the EO and their structures confirmed by Nuclear Magnetic Resonance (NMR) spectroscopy. Other major constituents of the EO were viridiflorene (27.3%), (E,E)-α-farnesene (1.4%), spirolepechinene and (E)-ß-caryophyllene (7.1% each), allo-aromadendrene (6.1%), camphor (1.7%), limonene (1.3%) and ß-phellandrene (4.6%). The enantiomeric composition of the EO monoterpene fraction was also studied, determining the enantiomeric excess and distribution of α-pinene, limonene, ß-phellandrene and camphor. The ethyl acetate extract of L. radula and L. paniculata were fractionated by column chromatography. Spathulenol, angustanoic acid E and 5-hydroxy-4',7-dimethoxy flavone were isolated from L. radula extract; ledol, guaiol and (-)-carnosol were found in L. paniculata.