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Mingquan Guo

Publications and source records attributed to Mingquan Guo.

5 recordsLinked to original sources
PubMed2004

Characterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometry.

Electrospray ionization tandem mass spectrometry (ESI-MS(n)) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and alpha-, beta- and gamma-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1 : 1 association constants (K(c)) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MS(n) condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD-R complexes can be elucidated by ESI-MS(n). The diagnostic fragmentation of CD-R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD-R complexes is beta-CD-R > alpha-CD-R > gamma-CD/R; beta-CD seems to bind R more strongly than the other CDs.

Cyclodextrins↗
PubMed2004

Structural elucidation and identification of alkaloids in Rhizoma Coptidis by electrospray ionization tandem mass spectrometry.

Simple, convenient, sensitive and accurate analytical methods are needed for the structural characterization and identification of alkaloid components in Rhizoma Coptidis in traditional Chinese herbal medicine, which has important bioactivity. In this work, the identification of alkaloid compounds in Rhizoma Coptidis was investigated by obtaining molecular mass information using electrospray ionization mass spectrometry (ESI-MS). Multi-stage tandem mass spectrometric (ESI-MS(n)) data for the alkaloid compounds were used for detailed structural characterization, then structure information was obtained by comparison of the fragmentation mechanisms of both alkaloids in Rhizoma Coptidis and standard samples of berberine, palmatine, coptisine and jatrorrhizine by MS. Based on the results obtained, the structure of a novel compound was elucidated. The results of the experiments demonstrate that ESI-MS(n) is a sensitive, selective and effective tool for the rapid determination of alkaloids in Rhizoma Coptidis.

Berberine↗
PubMed2003

Studies on the non-covalent complexes between oleanolic acid and cyclodextrins using electrospray ionization tandem mass spectrometry.

Non-covalent inclusion complexes formed between an anti-inflammatory drug, oleanolic acid (OA), and alpha-, beta- and gamma-cyclodextrins (CDs) were investigated by means of solubility studies and electrospray ionization tandem mass spectrometry (ESI-MS(n)). The order of calculated association constants (K(1 : 1)) of complexes between OA and different CDs in solution is in good agreement with the order of their relative peak intensities and the relative CID energies of the complexes under the same ESI-MS(n) conditions. These results indicate a direct correlation between the behaviors of solution- and gas-phase complexes. ESI-MS can thus be used to evaluate solution-phase non-covalent complexes successfully. The experimental results show that the most stable 1 : 1 inclusion complexes between three CDs and OA can be formed, but 2 : 1 CD-OA complexes can be formed with beta- and gamma-CDs. Multi-component complexes of alpha-CD-OA-beta-CD (1 : 1 : 1), alpha-CD-OA-gamma-CD (1 : 1 : 1) and beta-CD-OA-gamma-CD (1 : 1 : 1) were found in equimolar CD mixtures with excess OA. The formation of 2 : 1 and multi-component 1 : 1 : 1 non-covalent CD-OA complexes indicates that beta- and gamma-CD are able to form sandwich-type inclusion non-covalent complexes with OA. The above results can be partly supported by the relative sizes of OA and CD cavities by molecular modeling calculations. All the complexes allow the detection of gaseous deprotonated CD-OA complexes in the negative ion mode at high abundances. The relative stabilities of the CDs-OA inclusion complexes in the gas phase can be evaluated from the relative CID energies in the ion trap (alpha-CD-OA < beta-CD-OA < gamma-CD-OA) in the negative ion mode.

Cyclodextrins↗
PubMed2002

Analysis of flavonoid constituents from leaves of Acanthopanax senticosus harms by electrospray tandem mass spectrometry.

Three known flavonoids, quercetin, quercitrin (quercetin-3-0-rhamnoside) and rutin (quercetin-3-0 rutinoside), have been identified for the first time in the leaves of Acanthopanax senticosus Harms by using electrospray tandem mass spectrometry techniques (ESI-MS(n)). The flavonoid hyperin (quercetin-3-0-beta-galactoside), already known to be present, was also investigated. The diagnostic fragment ions of the aglycone quercetin were obtained in the ESI-MS(n) experiments, and a fragmentation mechanism proposed.

Araliaceae↗