Analysis of Volatile Organic Compounds fromDendranthema indicumvar.aromaticumby Headspace Gas Chromatography-Mass Spectrometry and Accurate Mass Measurement

Identification and functional analysis of terpene synthases revealing the secrets of aroma formation in Chrysanthemum aromaticum

C. aromaticum is widely cultivated for its aromatic, medicinal, and tea-applicable properties, earning the nickname 'lavender in composite'. Terpenoids are the major compounds of C. aromaticum fragrance. To reveal the molecular mechanisms of terpenoid biosynthesis in C. aromaticum, NGS and SMRT sequencing were employed to identify the key terpene synthase genes. A total of 59,903 non-redundant transcripts were obtained by the transcriptome analysis. Twenty-nine terpene synthase genes (TPSs) were identified, and phylogenetic analysis showed that they belong to four subfamilies of terpene synthases. Five CaTPSs were successfully cloned. Subcellular localization showed they were present in the nucleus and cytosol. Structure models of five terpene synthases were predicted, and molecular docking results showed good binding affinities with FPP/GPP. In vitro enzymatic tests showed that CaTPS7, CaTPS8, CaTPS10 and CaTPS20 could catalyze substrates to produce terpenoids. CaTPS7 and CaTPS20 were both able to effectively convert the precursor FPP into caryophyllene. CaTPS8 could convert FPP to trans-nerolidol and nerolidyl acetate, while CaTPS10 could convert FPP to elemene and aristolochene. This study lays the groundwork for further research to depict the metabolism network of terpenoid in C. aromaticum. These identical terpene synthase genes could be introduced into the cultivated chrysanthemums to enhance their fragrance.

Headspace-Low Water Absorption Trap Technique: Analysis of Low-Abundance Volatile Compounds from Fresh Artemisia Annua L. with GC-MS

Conventional headspace (HS) method could not meet the requirement of analyzing low-abundance volatile compounds in high water content samples. A HS-low water absorption trap technique coupled with gas chromatography-mass spectrometry was introduced to remove the large amount of water vapor; therefore, the low-abundance volatile compounds could be detected with better analytical sensitivity. With this method, a total of 81 volatile compounds were identified from fresh Artemisia annua L. by mass spectral library search, retention index and accurate mass measurement, which could make the qualitative results more accurate and reliable. These compounds belonged to different species, including terpene, cycloparaffin, aliphatic aldehyde, aromatic ketone, aromatic aldehyde and so on. The 2,5,6-trimethyl-1,3,6-heptatriene (8.23%) was the most principal compound, followed by γ-muurolene (6.80%), β-caryophyllenea (6.24%), 1,8-cineol (5.76%), 2-carene (5.65%), borneol (5.57%), isocaryophyllene (4.91%), bornylene (4.78%), camphene (4.30%) and β-pinene (4.26%) as the main components. The results indicated that this method presents a great potential for the trace analysis of volatile compounds in complex high water content samples.

GC-MS Analysis of the Composition of the Essential Oil from Dendranthema indicum Var. Aromaticum Using Three Extraction Methods and Two Columns

Dendranthema indicum var. aromaticum, which is an aromatic plant with a strong and special fragrance throughout the whole plant, is used for the treatment of colds and headaches, and as a mosquito repellant in Shennongjia, Hubei province, China. To analyze the composition of the essential oil from this medicinal herb, we developed a gas chromatography-mass Spectrometry (GC-MS) method including microwave-assisted extraction, hydrodistillation and direct headspace analysis in two different stationary phase columns. In total, 115 volatile compounds were identified, of which 90 compounds were identified using Rxi-5MS and 78 using HP-INNOWAX. Our results revealed that the oil was mainly composed of five categories of compound: oxygenated monoterpenes (28.76–78.10%), oxygenated sesquiterpenes (4.27–38.06%), sesquiterpenes (3.22–11.57%), fatty hydrocarbons (1.65–9.81%) and monoterpenes (0–3.32%). The major constituents are α-thujone, β-thujone, cis-sabinol, sabinyl acetate and (-)-neointermedeol.However, the essential oil composition in the published literature differs significantly. Therefore, a cluster analysis was carried out using the top ten compositions in the reported literature as well as this study, using Minitab software. To provide detailed information on plant origin, the ITS1-5.8s-ITS2 region was amplified and sequenced (Accession No. MF668250). Besides, in order to provide a macroscopic view of the chemical composition, the biosynthetic pathway of the main components was summarized according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and the published literatures.

GC-MS Analysis of the Volatile Constituents in the Leaves of 14 Compositae Plants

The green organs, especially the leaves, of many Compositae plants possess characteristic aromas. To exploit the utility value of these germplasm resources, the constituents, mainly volatile compounds, in the leaves of 14 scented plant materials were qualitatively and quantitatively compared via gas chromatography-mass spectrometry (GC-MS). A total of 213 constituents were detected and tentatively identified in the leaf extracts, and terpenoids (especially monoterpene and sesquiterpene derivatives), accounting for 40.45–90.38% of the total compounds, were the main components. The quantitative results revealed diverse concentrations and compositions of the chemical constituents between species. Principal component analysis (PCA) showed that different groups of these Compositae plants were characterized by main components of α-thujone, germacrene D, eucalyptol, β-caryophyllene, and camphor, for example. On the other hand, cluster memberships corresponding to the molecular phylogenetic framework, were found by hierarchical cluster analysis (HCA) based on the terpenoid composition of the tested species. These results provide a phytochemical foundation for the use of these scented Compositae plants, and for the further study of the chemotaxonomy and differential metabolism of Compositae species.

A Comparison of the Volatile Components of Cold Pressed Hamlin and Valencia (Citrus sinensis (L.) Osbeck) Orange Oils Affected by Huanglongbing

Volatiles from huanglongbing (HLB) symptomatic and asymptomatic cold pressed orange oils from Florida Hamlin and Valencia fruit were assessed. Qualitative gas-liquid chromatography studies showed the presence of several compounds (β-longifolene, perillene, and 4-decenal) which are not commonly identified in Citrus sinensis (L.) Osbeck oils. Oils derived from huanglongbing symptomatic fruit had lower concentrations of linalool, decanal, citronellol, neral, geranial, carvone, dodecanal, and 2-decenal and higher concentrations of citronellal compared to asymptomatic fruit. A comparison to historic literature of orange oil investigations before HLB was of issue in Florida orange crops showed lower levels of linalool, decanal, neral, and geranial in Hamlin peel oil samples, as well as higher levels of dodecanal. Valencia peel oil samples showed lower concentrations of linalool and increased concentration of citronellol and dodecanal. As a result of huanglongbing (HLB) phenomena, the concentrations of several important volatiles found in Hamlin and Valencia peel oil profiles have changed compared to historic values. Differences in volatile concentrations of symptomatic and asymptomatic HLB affected peel oil compounds in orange fruit are identified.

Gas chromatography-mass spectrometry analysis of essential oils from five parts of Chaihu (Radix Bupleuri Chinensis)

OBJECTIVE

To analyze the essential oils from flowers, leaves, stems, roots, and fruits of Chaihu (Radix Bupleuri Chinensis).

METHODS

We extracted essential oils from different parts of Chaihu (Radix Bupleuri Chinensis) using a steam distillation method. The essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS). Data were collected in full scan mode (m/z 60-600). Volatile components were identified based on their retention indices and by comparing their mass spectra with those in the National Institute of Standards and Technology 2005 database, assisted by tandem mass spectrometry information. The relative content of each constituent was determined by area normalization.

RESULTS

We identified 111 components, of which 12 were common to all 5 parts, 30 were found only in roots, 14 were found only in flowers, 6 were found only in leaves, 4 were found only in stems, and 17 were found only in fruits.

CONCLUSION

Our results show that the stems, flowers, leaves, and fruits of Chaihu (Radix Bupleuri Chinensis) contain a high concentration of essential oils, and that the exact composition of the essential oils differs among the plant parts. To develop new medicines and make full use of the Chaihu (Radix Bupleuri Chinensis) resource, it is important to characterize the essential oils from different parts of the plant. In future research, it will be important to determine the pharmacological effects of the various components and the essential oil mixtures.

Chemical compositions of the volatile extracts from seeds of Dendranthema nankingense and Borago officinalis

Volatile extracts from the seeds of Dendranthema nankingense Hand.-Mazz. and Borago officinalis L. were prepared using simultaneous distillation and extraction, and analyzed with gas chromatography–mass spectrometry on two capillary gas chromatography columns of different polarity. Ninety-five volatile compounds were identified in D. nankingense seeds, with hexanal, benzeneacetaldehyde, borneol, (−)-camphor, and 3-methyl-1-butanol being the predominant species. Sixty-five volatile compounds were identified in B. officinalis seeds, with 2-pentanone, 2,3-dihydro-benzofuran, 3-methyl butanal, and hexanal being the most abundant species. Thirty-three compounds, including short-chain aliphatic aldehydes, alcohols, and ketones, were common to both seeds. The volatile composition of both seeds varied significantly depending on their respective origins. The volatile terpenoids borneol and (−)-camphor could be key bioactive contributors to the characteristic flavor and cooling effects of D. nankingense. For the first time, coumaran was identified as an abundant species in plant seeds.

Application of gas chromatography-quadrupole-time-of-flight-mass spectrometry for post-target analysis of volatile compounds in Fructus Amomi

A post-target analysis method based on gas chromatography coupled to a high-resolution quadrupole time-of-flight mass analyzer is applied for the investigation of volatile compounds in Fructus Amomi. A series of narrow window extracted ion chromatograms at selected characteristic ions were performed. Chromatographic peaks with the same retention time in different extracted ion chromatograms was used to screen out the candidate compound. Identification was achieved by the accurate masses of several characteristic ions and the retention index of the peak. Forty six compounds, including 12 monoterpene compounds, were identified by conventional static headspace gas chromatography mass spectrometry and another six monoterpene compounds were found and identified by the post-target method. Post-target analysis is a useful strategy in qualitative research of natural products.

Analysis of the volatile compounds in Senecio scandens Buch-Ham by gas chromatography-tandem mass spectrometry based on diversified scan technologies

Static headspace gas chromatography-tandem mass spectrometry was used to identify volatile compounds from Senecio scandens Buch-Ham. The elemental composition of compounds was confirmed by exploiting the tandem mass spectra of isotopic peaks from the precursor ion. Some isomers were well distinguished by the diversified scan technologies of tandem mass spectrometry (MS/MS). The MS/MS included a product ion scan, a precursor ion scan and a neutral loss scan. The results showed that 46 volatile compounds were completely identified, and the great of majority compounds were α-pinene (11.93%), n-caproaldehyde (9.02%) and dehydrosabinene (6.22%). This qualitative method is convenient and accurate and can be considered as a complementary identification method for the qualitative analysis of volatile compounds in complex samples.