title: Isolation of the major chiral compounds from Bubonium graveolens essential oil by HPLC and absolute configuration determination by VCD.
abstract: The chirality issues in the essential oils (EOs) of leaves and flowers from Bubonium graveolens were addressed by chiral high-performance liquid chromatography (HPLC) with polarimetric detection and vibrational circular dichroism (VCD). The chemical compositions of the crude oils of three samples were established by gas chromatography / mass spectrometry (GC/MS). The well-known cis-chrysanthenyl acetate (1), oxocyclonerolidol (2), and the recently disclosed cis-acetyloxychrysanthenyl acetate (3), the three major chiral compounds, were isolated by preparative HPLC. The naturally occurring oxocycloneroledol (2), mostly found in the leaf oil (49.4-55.6%), presents a (+) sign in the mobile phase during HPLC on a chiral stationary phase (CSP) with a Jasco polarimetric detection. The naturally occurring cis-chrysanthenyl acetate (1) and cis-acetyloxychrysanthenyl acetate (3), mostly found in the flower EO (35.9-74.9% and 10.0-34.3%, respectively), both present a (-) sign. HPLC on a CSP with polarimetric detection is an unprecedented approach to readily differentiate the flower and leaf EOs according to their chiral signature. The comparison of the experimental and calculated VCD spectra of pure isolated 1, 2, and 3 provided their absolute configuration as being (1S,5R,6S)-(-)-2,7,7-trimethylbicyclo[3.1.1]hept-2-en-6-yl acetate 1, (2R,6R)-(+)-6-ethenyl-2,6-dimethyl-2-(4-methylpent-3-en-1-yl)dihydro-2H-pyran-3(4H)-one) 2 and (1S,5R,6R,7S)-(-)-7-(acetyloxy)-2,6-dimethylbicyclo[3.1.1]hept-2-en-6-yl]methyl acetate 3. Compounds 1, 2, and 3 were already known in B. graveolens but this is the first report of the absolute configuration of (+)-2 and (-)-3. The VCD chiral signatures of the crude oils were also recorded.
authors.affiliation: Aix-Marseille Université, EA4672 LISA Equipe METICA, Marseille, France.
authors.forename: Mohammed El-Amin
authors.initials: ME
authors.lastname: Said
authors.affiliation: Aix-Marseille Université, EA4672 LISA Equipe METICA, Marseille, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bombarda
authors.affiliation: Aix-Marseille Université, CNRS FR1739 Spectropole, Marseille, France.
authors.forename: Jean-Valère
authors.initials: JV
authors.lastname: Naubron
authors.affiliation: Aix-Marseille Université, EA4672 LISA Equipe METICA, Marseille, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Vanloot
authors.affiliation: Aix-Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Jean
authors.affiliation: Phytochemistry and Organic Synthesis Laboratory, University of Bechar, Bechar, Algeria.
authors.forename: Abdelkrim
authors.initials: A
authors.lastname: Cheriti
authors.affiliation: Aix-Marseille Université, EA4672 LISA Equipe METICA, Marseille, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Dupuy
authors.affiliation: Aix-Marseille Université, CNRS, Centrale Marseille, iSm2, Marseille, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Roussel
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000737:chemistry / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D008401:Gas Chromatography-Mass Spectrometry; D039821:Monoterpenes / Q000737:chemistry / Q000302:isolation & purification*; D009822:Oils, Volatile / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001643:Bridged Bicyclo Compounds; D039821:Monoterpenes; D009822:Oils, Volatile; C059209:chrysanthenyl acetate
keywords: Bubonium graveolens; chiroptical HPLC signature; enantiomers; essential oil; vibrational circular dichroism