Alain Jaquier

New Volatile Sulfur-Containing Constituents in a Simultaneous Distillation−Extraction Extract of Red Bell Peppers (Capsicum annuum)

An extract of red bell peppers ( Capsicum annuum) was prepared by simultaneous distillation-extraction (SDE, Likens-Nickerson). In addition to the already known (3 E)-3-hepten-2-one ( 1), the unsaturated C9-ketones 1-nonen-4-one ( 2), (2 E)-2-nonen-4-one ( 3), and (2 E,5 E)-2,5-nonadien-4-one ( 4), 2-methoxy-3-isobutylpyrazine ( 5), and heptane-2-thiol ( 6), we identified 19 new thiols (the aliphatic saturated and unsaturated thiols 14- 16, and 22- 27, the mercapto-ketones 12 and 13, the mercapto-alcohols 17, 18, and 30, the dithiols 19 and 28, the methylthio-thiols 20 and 21, and the thiophene-thiol 31) and the two new dithiolanes 10 and 29. All of them are structurally related to the unsaturated C7- and C9-ketones 1- 4. The free thiols were enriched using Affi-Gel 501 ( p-aminophenyl-mercuric acetate grafted on an agarose gel). The new compounds were confirmed by syntheses and were organoleptically evaluated.

Multidimensional gas chromatography hyphenated to mass spectrometry and olfactometry for the volatile analysis of citrus hybrid peel extract.

In this work, the volatile composition of the peel extract of limequat, a natural citrus hybrid, was investigated by using both conventional (gas chromatography-mass spectrometry [GC-MS], deconvolution) and more advanced (multidimensional GC-MS/olfactometry [MDGC-MS/O] and enantioselective [Es]-MDGC-MS/O) analytical techniques. Although the GC-MS analysis identified most of the components, some peaks remained unidentified. These unknown peaks were elucidated by deconvolution processing and using a selectable one-dimensional or two-dimensional GC-MS system equipped with an olfactometry port. The MDGC results, with both polar and chiral second dimensions, hyphenated to mass spectrometry and olfactometry, proved to be particularly useful for the identification and chiral characterization of coeluted trace compounds. In particular, the application of the Es-MDGC-MS/O configurations was used to confirm, by on-line enrichment, the presence of cis-δ-jasminlactone. This technique was fundamental for the reliable identification and exact determination of the enantiomeric distribution of this chiral compound, as well as for the sensorial evaluation of each enantiomer at the sniffing port.

Identification and Synthesis of New Volatile Molecules Found in Extracts Obtained from Distinct Parts of Cooked Chicken

Several chicken parts (skin, fat, juice) were cooked in different ways (roasting, simmering) and investigated separately for their volatile composition. In-depth GC/MS analysis of the separate fractions revealed several unknown molecules. Mass spectra interpretation allowed us to identify nine molecules for the first time in chicken, including cyclic aldehydes, cyclic ketones, and new δ-lactones containing an unsaturated linear chain. Identification was confirmed by chemical synthesis followed by comparison of the mass spectra and linear retention indices. The natural occurrence of five of these molecules is reported here for the first time in a natural product.

A new natural furan and some related compounds

A new furan, (E)-6-methyl-6-(5-methyl-2-furyl)hep-3-en-2-one (1), was identified in a lavender absolute, in an extract of prunes, in extracts of green and black tea and in an extract of spinach leaves. Its structure was confirmed by condensation of 2-methylfuran and 3-methylbut-2-enal under acidic conditions, followed by an aldol condensation with acetone. Two related ketones as well as their corresponding alcohols were also prepared. The organoleptic evaluations of all compounds are presented.

Comparative analysis of three Australian finger lime (Citrus australasica) cultivars: identification of unique citrus chemotypes and new volatile molecules.

The volatile constituents of the peel of three cultivars of Australian finger lime (Citrus australasica) were investigated: Alstonville, Judys Everbearing and Durhams Emerald. Both qualitative and quantitative GC-MS analyses were performed on their peel solvent extract. The results showed that the unique phenotypes of finger lime are also correlated to unique molecular compositions. Each cultivar revealed a different chemotype: limonene/sabinene for cv. Alstonville, limonene/citronellal/isomenthone for cv. Judys Everbearing, and limonene/citronellal/ citronellol for cv. Durhams Emerald. To the best of our knowledge, these chemotypes have never been reported in any other citrus species. Furthermore, the amounts of some volatile constituents (γ-terpinene, α-pinene, β-pinene, citral), which are generally the major constituents besides limonene in lime species, were surprisingly low in the three cultivars. Comparative GC-MS analysis also showed that some volatile molecules tended to be specific to one cultivar and could therefore be considered as markers. Moreover six molecules were reported for the first time in a citrus extract and confirmed by synthesis. Heart-cutting enantioselective two-dimensional GC-MS was performed to determine the enantiomeric distribution of the major chiral constituents. The combined data on three finger lime cultivars gives evidence of their divergence from other citrus species.