Selective BuChE Inhibitory Activity, Chemical Composition, and Enantiomeric Content of the Essential Oil from Salvia leucantha Cav. Collected in Ecuador

The essential oil (EO) of Salvia leucantha Cav. was isolated by steam distillation of the aerial parts collected in the South of Ecuador. Its physical properties were evaluated and the chemical composition of the oil was determined by GC-MS and GC-FID analyses using two chromatographic columns, DB-5ms and HP-INNOWax. Six major compounds were identified, namely, the sesquiterpenes 6.9-guaiadiene (19.14%), (E)-caryophyllene (16.80%), germacrene D (10.22%), (E)-β-farnesene (10.00%), and bicyclogermacrene (7.52%), and the monoterpenoid bornyl acetate (14.74%). Furthermore, four pairs of enantiomers were determined by enantioselective GC-MS of the essential oil. (−)-germacrene D and (+)-α-pinene showed the highest enantiomeric excess (ee%). In an in vitro assay, the essential oil demonstrated an interesting inhibitory activity of the enzyme butyrylcholinesterase (BuChE), with an IC50 = 32.60 µg/mL, which is the highest determined for a Salvia species. In contrast, the oil was weakly active against acetylcholinesterase (AChE) with an IC50 > 250 µg/mL.

A Novel Chemical Profile of a Selective In Vitro Cholinergic Essential Oil from Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae), a Native Andean Species of Ecuador

A novel chemical profile essential oil, distilled from the aerial parts of Clinopodium taxifolium (Kunth) Govaerts (Lamiaceae), was analysed by Gas Chromatography-Mass Spectrometry (GC-MS, qualitative analysis) and Gas Chromatography with Flame Ionization Detector (GC-FID, quantitative analysis), with both polar and non-polar stationary phase columns. The chemical composition mostly consisted of sesquiterpenes and sesquiterpenoids (>70%), the main ones being (E)-β-caryophyllene (17.8%), α-copaene (10.5%), β-bourbonene (9.9%), δ-cadinene (6.6%), cis-cadina-1(6),4-diene (6.4%) and germacrene D (4.9%), with the non-polar column. The essential oil was then submitted to enantioselective GC analysis, with a diethyl-tert-butyldimethylsilyl-β-cyclodextrin diluted in PS-086 chiral selector, resulting in the following enantiomeric excesses for the chiral components: (1R,5S)-(−)-α-thujene (67.8%), (1R,5R)-(+)-α-pinene (85.5%), (1S,5S)-(−)-β-pinene (90.0%), (1S,5S)-(−)-sabinene (12.3%), (S)-(−)-limonene (88.1%), (S)-(+)-linalool (32.7%), (R)-(−)-terpinen-4-ol (9.3%), (S)-(−)-α-terpineol (71.2%) and (S)-(−)-germacrene D (89.0%). The inhibition activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) of C. taxifolium essential oil was then tested, resulting in selective activity against BChE with an IC50 value of 31.3 ± 3.0 μg/mL (positive control: donepezil, IC50 = 3.6 μg/mL).

Enantioselective GC Analysis of C3–Oxygenated p-Menthane type Indian Mentha Spicata var. Viridis ‘Ganga’ Essential Oil

Essential oil of Mentha spicata L. var. viridis ‘Ganga’, an indigenously developed variety, was chemically profiled using various gas chromatographic techniques. Piperitenone oxide was characterized as the most exclusive constituent (69.7%) along with a new C3–oxygenated p-menthane alcohol, diosphenolene (1.6%). Enantiomeric discrimination revealed (4 S)-(-)-limonene, ( R)-(-)-linalool and (1 S,2 S)-(+)-piperitenone oxide as predominant enantiomers. The oil contained mainly C3–oxygenated p-menthane monoterpenoids, which are distinctive of peppermint, instead of the characteristic C6–oxygenated class of spearmint. The present findings will aid in understanding the pathway and cause of C3-oxygenation in a spearmint taxon. The essential oil and pure piperitenone oxide showed growth inhibiting properties and thus, may be utilized in antifungal preparations for disease management of medicinal and aromatic plants.

Algicidal lactones from the marine Roseobacter clade bacterium Ruegeria pomeroyi

Volatiles released by the marine Roseobacter clade bacterium Rugeria pomeroyi were collected by use of a closed-loop stripping headspace apparatus (CLSA) and analysed by GC–MS. Several lactones were found for which structural proposals were derived from their mass spectra and unambiguously verified by the synthesis of reference compounds. An enantioselective synthesis of two exemplary lactones was performed to establish the enantiomeric compositions of the natural products by enantioselective GC–MS analyses. The lactones were subjected to biotests to investigate their activity against several bacteria, fungi, and algae. A specific algicidal activity was observed that may be important in the interaction between the bacteria and their algal hosts in fading algal blooms.