Chemical and Enantioselective Analysis of the Leaf Essential Oil from Piper coruscans Kunth (Piperaceae), a Costal and Amazonian Native Species of Ecuador

Abstract

In the present study, an essential oil was distilled from the leaves of <i>Piper coruscans</i> Kunth, a native Amazonian species belonging to the family Piperaceae and quite common in Ecuador. The chemical analysis was performed by GC-MS (qualitative) and GC-FID (quantitative), on polar and non-polar columns, detecting a total of 58 compounds of which 52 were identified. All the identified compounds were quantified. The essential oil was mainly constituted of sesquiterpenes (54.1-55.0%) and oxygenated sesquiterpenoids (32.5-33.6%), the major constituents being: (<i>E</i>)-β-caryophyllene (24.1-25.0%), α-humulene (11.6-12.0%), caryophyllene oxide (9.3-10.9%), linalool (4.5-5.2%), humulene epoxide II (3.6-4.1%), (<i>E</i>)-nerolidol (3.7-4.0%), α-copaene (3.7-3.9%), α-muurolol (3.4-3.7%), α-selinene (3.4-3.5%), β-selinene (3.1-3.3%), and one undetermined oxygenated sesquiterpenoid (3.1-3.3%). The aqueous phase (hydrolate) of the distillation process was also submitted to chemical analysis, showing linalool as the main organic compound in solution, with a concentration of 12.3-15.7 mg/100 mL. The essential oil was than analyzed for the enantiomeric distribution of its monoterpene constituents, affording the following enantiomeric excesses in two β-cyclodextrin-based enantioselective columns: (1<i>S</i>,5<i>S</i>)-(-)-α-pinene (60.0-69.6%), (1<i>S</i>,5<i>S</i>)-(-)-β-pinene (5.2-7.2%), (<i>R</i>)-(-)-α-phellandrene (72.5-78.2%), (<i>R</i>)-(+)-limonene (28.6%) and (<i>R</i>)-(-)-linalool (1.8-3.1%).