The key role of ¹³C NMR analysis in the identification of individual components of Polyalthia longifolia leaf oil

Abstract

Polyalthia longifolia produces sesquiterpene-rich essential oils (EOs) whose compositions varied substantially from sample to sample depending on the origin of the plant (Nigeria and Vietnam). Nothing is known about the phytochemistry of Ivoirian P. longifolia. The aim of the present study was to characterize Ivoirian P. longifolia through the chemical composition of the leaf oil and to develop a strategy that allows the identification of minor oxygenated sesquiterpenes whose MS data are not compiled in commercial or laboratory-constructed MS libraries. The EO was submitted to gas chromatography (GC) retention index (RI), GC-mass spectrometry (MS) and 13 C nuclear magnetic resonance (NMR) analysis. Then hydrocarbons and oxygenated components were separated and the oxygenated fraction was chromatographed on silica gel. The fractions were analysed by GC(RI) and 13 C NMR. Seventy compounds accounting for 91.8% of the EO were identified. Sesquiterpene hydrocarbons, (E)-β-caryophyllene (27.8%), α-zingiberene (20.0%) and allo-aromadendrene (15.0%), were the major components. Various oxygenated sesquiterpenes whose MS data were not compiled in commercial and laboratory-made MS libraries were identified by comparison of their chemical shift values in the spectrum of the fraction of CC with those reported in the literature and compiled in a laboratory-constructed 13 C NMR data library. The composition of the investigated Ivoirian P. longifolia oil sample presented similarities and differences with Nigerian and Vietnamese oils. Combined analysis of Ivoirian P. longifolia EO by chromatographic and spectroscopic techniques including 13 C NMR without isolation of the components, appeared particularly efficient to identify minor components of EOs, whose MS spectra are insufficiently differentiated or MS data are not compiled in commercial and lab-constructed MS libraries.

Germacra‐1(10),5‐dien‐4α‐ol in Fortunella sp. leaf oils

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Discrimination and Characterization of Two Mediterranean Species from theLaurenciaComplex (Rhodomelacea) Using anNMR‐Based Metabolomic Approach

“…A computer‐assisted method previously developed in our laboratory which is based on 13 C‐NMR spectroscopy of crude extracts was applied . An in‐house library containing spectral data of components (about 2000) from marine macro algae was consulted.…”

Chemical Composition and In Vitro Evaluation of Antimicrobial, Antioxidant and Antigerminative Properties of the Seed Oil from the Tunisian Endemic Ferula tunetana Pomel ex Batt.

“…Identification of compounds by GC ( RI ) and GC/MS was based on comparison of their retention indices with those of authentic samples and by comparison of their mass spectra with those of pure compounds compiled in computerized libraries . All the components were also identified by 13 C‐NMR spectroscopy, following the method developed and computerized at the University of Corsica, using home‐made software, by comparison with spectral data of reference compounds compiled in a laboratory‐built library …”