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Keteleeria davidiana (C.E.Bertrand) Beissn. is a species of conifer native to southern China, Laos and Vietnam. The species has been listed as vulnerable in Vietnam. Essential oil samples have been isolated from leaves, twigs and wood, and their compositions investigated for the first time by combination of chromatographic and spectroscopic techniques [GC-FID, GC-MS and13C NMR]. The composition of leaf essential oil was dominated by α-pinene (28.1%), β-pinene (15.8%) and (E)-β-caryophyllene (13.8%). Twig essential oil contained mainly α-pinene (37.9%) and β-pinene (24.7%) accompanied by (E)-β-caryophyllene (8.3%) and β-phellandrene (7.5%). Lastly, α-pinene (27.9%), α-terpineol (20.3%) and (E)-β-caryophyllene (20.8%) were predominant in wood essential oil. [ABSTRACT FROM AUTHOR]

The needle and cone essential oils of Pinus fenzeliana Hand-Mazz. (Pinus kwangtungensis Chun & Tsiang) collected in Hang Kia-Pa Co Nature Reserve, Hoa Binh province were obtained by hydrodistillation and analyzed by a combination of GC-FID, GC-MS and NMR (Gas Chromatography/Gas Chromatography-Mass Spectrometry/Nuclear Magnetic Resonance (NMR) analysis). The oil yields were 0.2% and 0.37% respectively (v/w on dry weight basis). Twenty-seven compounds were detected in both needle and cone oils, accounting for 98.0% and 98.2% of the whole composition, respectively. The main components identified in the needle oil were α-pinene (20.7%), β-pinene (11.3%), δ-3-carene (32.2%), limonene (8.0%) and E-β-caryophyllene (7.1%). The cone oil contained mainly α-pinene (19.3%), β-pinene (45.4%), δ-3-carene (3.5%), limonene (12.7%) and E-β-caryophyllene (3.4%). This is the first report on the chemical composition of the cone essential oil of P. fenzeliana from Vietnam. [ABSTRACT FROM AUTHOR]

Citral (3,7‐dimethyl‐2,6‐octadienal), a mixture of geranial and neral (two stereoisomeric monoterpene aldehydes), is considered an important raw material in the fields of fragrance, pharmaceutical, food and cosmetic industries. It is a well‐known biologically active compound present in various essential oils. A fast and reliable experimental method was developed and validated in order to quantify citral in essential oils using 1H NMR spectroscopy (experiment time at the minute level). The quantitative procedure, using anisole as internal standard, showed a perfect linearity of measurements (R2 = 0.9999), a very good accuracy (relative errors comprised between −1.9% and 0.3%) and an excellent precision (reproducibility 17.8 mg ± 1.0%). The procedure was also checked with three mixtures of weighted monoterpenes and the contents of citral, measured by GC and 1H NMR, were absolutely comparable. Then, the method was successfully applied to measure the contents of citral in 10 commercially available essential oils. Among the investigated samples, citral varied from 2.9% (Zingiber officinalis) to 90.6% (Bakhousia citriodora). [ABSTRACT FROM AUTHOR]

Glyptostrobus pensilis (Staunton ex D. Don) K. Koch is a critically endangered species, native to southeastern China and also very locally found in Dak Lak Province, Vietnam. Essential oil isolated from leaves is a monoterpene-rich oil containing mainly limonene (33.3%), α-pinene (23.4%) and bornyl acetate (9.2%). The composition of G. pensilis wood oil is rather complex and the identification of individual components needed fractionation over column chromatography. The main components, identified by GC(RI), GC-MS and 13C NMR, were cedrol (29.3%), occidentalol (6.6%) and occidentalol isomer (5.9%). [ABSTRACT FROM AUTHOR]

Cladanthus mixtus (L.) Chevall., Asteraceae, also known as Moroccan chamomile, is a spontaneous, annual plant growing wild in North-Western Morocco. Economically, the essential oil of C. mixtus is of high interest, Morocco being the only supplier on the international market. Two essential oil samples (EO) were isolated from aerial parts of Cladanthus mixtus (L.) Chevall., and analyzed by a combination of chromatographic and spectroscopic techniques (gas chromatography (GC) in combination with retention indices (RI), gas chromatography-mass spectrometry (GC/MS), and 13C NMR spectroscopy). Computer matching against the in-house 13C NMR library allowed the identification of the eight components at appreciable contents, namely 3,6,6,9-bis-epoxy-farnesa-1,7(14),10-triene, and its 3-epi, 9-epi, and 3,9-diepi epimers, and 6,9-epoxy-farnesa-1,7(14),10-trien-3-ol and its 3-epi, 6-epi, and 3,6-diepi epimers. Our results confirm the tremendous chemical variability of Moroccan C. mixtus essential oil and the usefulness of 13C NMR analysis, in combination with GC(RI), for the identification of uncommon oxygenated sesquiterpenes that induce an original composition. [ABSTRACT FROM AUTHOR]

Research was conducted to attempt the preparation of various substituted cyclobutylmethyl cations and the preparation as well as the characterization of the persistent cyclobutyldicyclopropylmethylium cation. Variable-temperature NMR studies of the cation was also performed. Results indicate that primary and secondary cyclobutylmethyl cations were elusive in superacidic media even at low temperatures. It was also found that cyclobutylmethyl cations readily undergo ring expansion-rearrangement to yield the corresponding cyclopentyl cations.

The curriculum of computer-aided chemistry needs to be reviewed in light of recent and continuing hardware and software developments toward greater ability and faster speed. Computers in education were first mentioned in the Journal of Chemical Education in 1959 in one article. Since then, computers have become widely used in the classroom because of affordable, fast microprocessors. Molecular modeling using a computer enables students to perform complex tasks that were previously beyond them such as computing models at the semiempirical level.

Lecomte is endemic to the central highlands of Vietnam. It is also known as Krempf's pine or flat-needled pine. Two essential oil samples have been isolated from leaves and branches, respectively, and analyzed by a combination of chromatographic and spectroscopic techniques [GC(FID), GC-MS and 13C NMR]. The compositions of both oil samples were dominated by monoterpene hydrocarbons, α-pinene, limonene and myrcene. Sesquiterpene hydrocarbons were represented by (E)-β-caryophyllene and germacrene D. Camphorene (meta isomer) was identified at low content. The compositions of essential oil samples from P. krempfii have been compared with those of other essential oils from various species of Vietnamese pines. [ABSTRACT FROM AUTHOR]

This work is a contribution to the characterization of aromatic and medicinal plants from Côte d'Ivoire. To date, no phytochemical investigation was reported on Isolona dewevrei. Thus, the aim of this study was to investigate for the first time, the chemical composition of the leaf essential oil from I dewevrei. Two essential oil samples (S1, S2) were analysed by combination of chromatographic [GC(FID) and GC(RI)] and spectroscopic [MS, 13C‐NMR] techniques. As several compounds remained unidentified, particularly in sample S1, this oil was fractionated on silica gel column, leading to the isolation and structural elucidation of four new natural compounds by QTOF‐MS, 1D and 2D‐NMR analyses. These new natural sesquiterpenes were identified as (5αH,10βMe)‐6,12‐oxido‐elema‐1,3,6,11(12)‐tetraene, 6,12‐oxido‐germacra‐1(10),4,6,11(12)‐tetraene, (1βH,5βH)‐6,12‐oxido‐guaia‐6,10(14),11(12)‐trien‐4α‐ol and germacra‐1(10),4,7(11)‐trien‐6,12‐γ‐lactone. Finally, sixty‐eight constituents were identified in both investigated essential oil samples. They accounted for 96.1 and 97.3%, respectively, of the whole chemical composition of S1 and S2. Leaf essential oil from Idewevrei is very rich in sesquiterpenes. Indeed, its majority compounds were germacrene B (20.8 and 24.8%), (5αH,10βMe)‐6,12‐oxido‐elema‐1,3,6,11(12)‐tetraene (10.3 and 0.3%, new compound), germacrene D (7.5 and 17.8%), (Z)‐β‐ocimene (7.8 and 9.7%),γ‐elemene (6.9 and 7.5%) and (E)‐β‐caryophyllene (6.8 and 3.5%). The contents of thermolabile components were assessed by combination of GC(FID) and 13C‐NMR. [ABSTRACT FROM AUTHOR]