Fragmentation pathways of protonated coumarin by ESI-QE-Orbitrap-MS/MS coupled with DFT calculations.

Coumarin is one of the basic structures of naturally oxygen heterocyclic compound, which was investigated in this paper for its gas-phase fragmentation behaviors using electrospray quadrupole extractive orbitrap mass spectrometry in the positive mode. The possible fragmentation pathways were proposed based on electrospray ionization (ESI)- mass spectrometry (MS)/MS data and theory calculation. The elimination of two CO and CO2 was observed for protonated coumarin, which was followed by the formation of a stabilized seven-, six-, and five-membered ring carbocation by loss of C2H2. The possible protonation sites occurred at Oxygen 11 atom of coumarin were the main fragmentation pathways. The relative abundance of characteristic fragment ions and the energy-resolved breakdown curves were used to confirm the cleavage mechanism of protonated coumarin. The methodology and results of present work would contribute to the chemical structure identification of other coumarins.

[Chromatographic fingerprint peak matching of Semen Cassiae by asymptotic window orthoganality projection analytical method].

OBJECTIVE: To investigate the principle and basis about the chromatographic fingerprint peak matching of Semen Cassiae by the asymptotic window orthogonal projection analytical method. METHOD: The samples of Semen Cassiae were hydrolyzed in the 1.5 mol x L(-1) hydrochloride acid and then reflux extracted with chloroform. The chromatographic condition was that the HPLC was run on Agilent 1100 column, Zorbax Eclipse XDB-C18 (4.6 mm x 250 mm, 5 microm). The protected column was Scienhome C18 column (3.0 mm x 20 mm, 5 microm) with acetonitrile-water (0.1% phosphoric acid) as mobile phase in gradient elution at a flow rate of 1.0 mL x min(-1). The detection wavelength and reference wavelength were 278 nm and 550 nm, respectively. RESULT: The characteristic fingerprint collection of illustrative plates of Semen Cassiae were obtained with different HPLC instruments and chromatographic columns. And the asymptotic window orthogonal projection analytical method was used to decide the chromatographic fingerprint peak matching of Semen Cassiae, promptly and prapidly. CONCLUSION: The asymptotic window orthogonal projection analytical method can progress the matching of different fingerprint collection of illustrative plates peak matching well and truly.

Fragmentation characteristics of hydroxycinnamic acids in ESI-MSn by density functional theory.

This work aims to analyze the electrospray ionization multistage mass spectrometry (ESI-MSn ) fragmentation characteristics of hydroxycinnamic acids (HCAs) in negative ion mode. The geometric parameters, energies, natural bond orbitals and frontier orbitals of fragments were calculated by density functional theory (DFT) to investigate mass spectral fragmentation mechanisms. The results showed that proton transfer always occurred during fragmentation of HCAs; their quasi-molecular ions ([M - H]- ) existed in more than one form and were mainly with the lowest energy. The fragmentation characteristics included the followings: (1) according to the different substitution position of phenolic hydroxyl group, the ring contraction reaction by CO elimination from benzene was in an increasingly difficult order: m-phenolic hydroxyl > p-phenolic hydroxyl > o-phenolic hydroxyl; and (2) ortho effect always occurred in o-dihydroxycinnamic acids (o-diHCAs), i.e. one phenolic hydroxyl group offered H+ , which combined with the other one to lose H2 O. In addition, there was a nucleophilic reaction during ring contraction in diHCAs that oxygen atom attacked the carbon atom binding with the other phenolic hydroxyl to lose CO2 . The fragmentation characteristics and mechanism of HCAs could be used for analysis and identification of such compounds quickly and effectively, and as reference for structural analogues by ESI-MS. Copyright © 2017 John Wiley & Sons, Ltd.

[Comparison of volatile oil chromatographic fingerprints of rhizoma curcumae longae and rhizoma wenyujin concisum].

To explore the same and difference of chemical components between the chromatographic fingerprints of volatile oil of Rhizoma Curcumae Longae and Rhizoma Wenyujin Concisum, the chromatographic/spectroscopic data of fingerprints were comparative analyzed using modified window target-testing factor analysis method. The results of comparisons showed that ten chemical components present in Rhizoma Curcumae Longae are absent in Rhizoma Wenyujin Concisum, while nine chemical components are present in Rhizoma Wenyujin Concisum but absent in Rhizoma Curcumae Longae. Also, nine common components are both present in Rhizoma Curcumae Longae and Rhizoma Wenyujin Concisum.

Temperature-programmed retention indices for gas chromatography-mass spectroscopy analysis of plant essential oils.

A total of 95 volatile compounds from the essential oil in buds of Syringa oblata Lindl (lilac) were identified by gas chromatography-mass spectrometry (GC-MS) combined with heuristic evolving latent projections (HELP) and moving subwindow searching (MSS). The identified compounds are mainly aliphatic, terpenes and aromatic compounds. Their temperature-programmed retention indices (PTRIs) on HP-5MS and DB-35MS at three heating rates of 2, 4 and 6 degrees C/min from 80 to 290 degrees C were obtained, which showed that aliphatic compounds give nearly constant PTRIs and PTRIs of terpenoids do not vary much at different heating rates. But PTRIs of aromatic compounds exhibit relatively large temperature dependence. PTRIs vary much more on DB-35MS than those on HP-5MS according to the compound types. In general, differences of PTRIs between the two columns increase from aliphatic compounds to terpenoids to polycyclic aromatic compounds. The PTRIs in different heating rates were used as cross-references in the identification of components in the essential oil. When they were used in analysis of essential oil from flowers of lilac, good results were obtained. These PTRIs would be a part of our PTRI database being constructed on components from plant essential oils. The results also showed that efficiency and reliability were improved greatly when chemometric method and PTRIs were used as assistants of GC-MS in identification of chemical components in plant essential oils.

[Chemical components in essential oils from tender branches and leaves of Rhododendron].

AIM: To analyze and compare the compositions in essential oils from branches and leaves of Rhododendron simsii Planch. and Rhododendron naamkwanense Merr. METHODS: Essential oils were extracted by water distillation according to Chinese Pharmacopoeia and analyzed by capillary gas chromatography-mass spectrometry as well as chemometrics resolution method and authentic compounds. The relative contents of each component in the essential oils were obtained by normalization of peak areas. RESULTS: A total of 124 components were identified, of which 48 compounds were existed in both of the samples. Ninety four compounds accounted for 84.47% of the essential oil from Rhododendron simsii Planch. and seventy eight components accounted for 90.25% of the total essential oil from Rhododendron naamkwanense Merr. were identified. 72.76% and 88.07% of the components in Rhododendron simsii Planch and Rhododendron naamkwanense Merr., respectively, included oxygen element. They are mainly terpenol, acids and esters. 1-octen-3-ol (4.00%, 7.90%), 1,6-octadien-3-ol, 3,7-dimethyl-(12.60%, 3.48%), 9,12,15-octadecatrienoic acid, [Z, Z, Z]- (1.15%, 45.34%), phytol (15.21%, 8.56%), p-menth-1-en-8-ol (2.15%, 3.29%), and 9,12,15-octadecatrienoic acid, ethyl ester, [Z,Z,Z]- (9.16%, 8.01%) were their common main compounds, which accounted for 44. 27% and 76.58% of the total amount of the two essential oil samples, respectively. In addition, n-hexadecanoic acid (7.73%), 9,12-octadecadienoic acid (1.85%) and tetracosanoic acid, methyl ester (1.38%) were also the main compounds in essential oil from Rhododendron simsii Planch. CONCLUSION: Much higher reliability and accuracy were obtained with the help of chemometrics resolution method and authentic n-alkane standard solutions than those of using GC-MS alone.

Metabonomics study of the protective effects of Lonicera japonica extract on acute liver injury in dimethylnitrosamine treated rats.

A metabonomics approach, consisting of gas chromatography coupled to mass spectrometry (GC/MS) and a multivariate statistical technique, was developed to estimate the protective effects of Lonicera japonica extract (LJE) on acute liver injury. A high dose of dimethylnitrosamine (DMN) was used to induce an acute stage of hepatic injury in 21 male Wistar rats. The rats were divided into three groups: normal, model and treatment. Pathological changes, particularly fibrosis, were also examined by Azan staining. The results indicate that clear and consistent biochemical changes occur. Nine candidate biomarkers for DMN treatment and LJE intervention under controlled conditions were identified using chemometric analysis. Pathological analysis suggests that LJE has a protective effect to the liver. This work suggests that a metabonomics approach can be used to estimate pharmacodynamic action of naturally occurring drugs in a dynamic and non-invasive way.

Studies on the origin of the voltammetric response of the PC-3 cell suspension.

A novel experimental method was developed to study the origin of the voltammetric response of human prostate cancer (PC-3) cell suspension as a model in consideration of the biological characters of living cells. The presence of guanine and xanthine in the cell eluent secreted by the living cells was verified by HPLC assay with a DAD system and chemometric method. Comparative studies of voltammetric behaviors of the PC-3 cell suspension, the PC-3 cell eluent, and the PC-3 cell sediment re-suspension showed that the voltammetric response of the PC-3 cells was given by xanthine and guanine bases in the PC-3 cell eluent, not by the cells. Linear relationship between the peak currents of guanine and xanthine in the cell eluent and the cell concentrations was found. Other factors, such as the cell secretion time and the immersion time of the multiwalled carbon nanotubes modified glassy carbon electrode (MWCNTs-modified GCE) in the cell eluent, also influenced the intensity of the peak currents. The biochemical mechanisms of the voltammetric behavior for the cell suspension were proposed.

Comparative analysis of volatile components from Clematis species growing in China.

The volatile components between stems and roots and also among five Clematis species from China were studied and analyzed by gas chromatography-mass spectrometry (GC-MS) combined with alternative moving window factor analysis (AMWFA), a new chemometric resolution method. Identification of the compounds was also assisted by comparison of temperature-programmed retention indices (PTRIs) on HP-5MS with authentic samples included in our own laboratory database under construction. A total of 153 different compounds accounting for 86.6-96.5% were identified and significant qualitative and quantitative differences were observed among the samples. The major volatile components in different essential oils from Clematis species were n-hexadecanoic acid and (Z,Z)-9,12-octadecadienoic acid. Our work further demonstrated chemometric resolution techniques upon the two-dimensional data and PTRIs can provide a complementary and convenient method for fast and accurate analysis of complex essential oils.