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Matrix-free thin-layer chromatography/laser desorption ionization mass spectrometry for facile separation andidentification of medicinal alkaloids
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Analytical Chemistry.
Plant Biology Division, Institute of Biological Sciences, University of the Philippines Los Banos, College, Laguna 4031, The Philippines.
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2009 (English)In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 23, no 23, 3655-3660 p.Article in journal (Refereed) Published
Abstract [en]

Quaternary protoberberine alkaloids belong to a pharmaceutically important class of isoquinoline alkaloids associated with bactericidal, fungicidal, insecticidal and antiviral activities. As traditional medicine gains wider acceptance, quick and robust analytical methods for the screening and analysis of plants containing these compounds attract considerable interest. Thin-layer chromatography (TLC) combined with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful technique but suffers from dilution of the TLC bands resulting in decreased sensitivity and masking of signals in the low-mass region both due to addition of matrix. This study integrates for the first time conventional silica gel TLC and laser desorption ionization mass spectrometry (LDI-MS) thus eliminating the need for any external matrix. Successful separation of berberine (Rf = 0.56) and palmatine (Rf = 0.46) from Berberis barandana including their identification by MS are demonstrated. Furthermore, a robust electrospray ionization (ESI)-MS method utilizing residual sample from TLC for quantification of berberine applying selected reaction monitoring and standard addition method is presented. The amount of berberine in the plant root prepared for the study was determined to be 0.70% (w/w). Copyright © 2009 John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
2009. Vol. 23, no 23, 3655-3660 p.
Identifiers
URN: urn:nbn:se:su:diva-33258DOI: 10.1002/rcm.4297OAI: oai:DiVA.org:su-33258DiVA: diva2:282780
Available from: 2009-12-21 Created: 2009-12-21 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Mass Spectrometry of Biologically Active Small Molecules: Focusing on polyphenols, alkaloids and amino acids
Open this publication in new window or tab >>Mass Spectrometry of Biologically Active Small Molecules: Focusing on polyphenols, alkaloids and amino acids
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The foci of this dissertation are on advanced liquid chromatography (LC) separation and mass spectrometry (MS) techniques for the analysis of small bioactive molecules. In addition to discussing general aspects of such techniques the results from analyses of polyphenols (PPs), alkaloids and amino acids published in five appended studies are presented and discussed. High efficiency and well understood principles make LC the method of choice for separating analytes in many kinds of scientific investigations. Moreover, when LC is coupled to an MS instrument, analytes are separated in two stages: firstly they are separated and pre-concentrated in narrow bands using LC and then separated according to their mass-to-charge (m/z) ratios in the MS instrument. Some MS instruments can provide highly accurate molecular weight measurements and mass resolution allowing identification of unknown compounds based purely on MS data, thus making prior separation unnecessary. However, prior separation is essential for analyzing substances in most complex matrices – especially useful is the ultra-high performance LC (UHPLC). The advantages of using UHPLC rather than HPLC for the analysis of PPs in tea and wine were evaluated in one of the studies this thesis is based upon. The phenolic composition of red wine was also examined, using a novel LDI technique, following solid phase extraction (SPE). A class of small aromatic molecules (medicinally important alkaloids) also proved to be amenable to straightforward analysis, by thin layer chromatography (TLC) work-up followed by LDI-MS. Finally, a LC-MS method for monitoring neurotoxins (β-N-methyl-amino-L-alanine and 2,3-diaminobutyric acid) in complex biological matrices was developed and applied. Overall, the studies show that careful attention to the physicochemical properties of analytes can provide insights that can greatly facilitate the development of alternative methods to analyze them, e.g. by LDI.

Place, publisher, year, edition, pages
Stockholm: Department of Analytic Chemistry, Stockholm University, 2010. 61 p.
Keyword
LC-MS, LDI, Mass spectrometry, HPLC, UHPLC, polyphenols, phenolic acids, BMAA
National Category
Analytical Chemistry Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-33233 (URN)978-91-7155-982-1 (ISBN)
Public defence
2010-01-29, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In press. Paper 5: Manuscript.

Available from: 2010-01-07 Created: 2009-12-21 Last updated: 2015-06-08Bibliographically approved
2. Novel clean-up, concentration and laser desorption/ionization strategies for mass spectrometry
Open this publication in new window or tab >>Novel clean-up, concentration and laser desorption/ionization strategies for mass spectrometry
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Despite valuable advantages of mass spectrometry (MS) techniques they still have drawbacks that need to be overcome, notably their sensitivity to various kinds of interfering substances and associated difficulties involved in detecting signals from analytes present in trace quantities. Thus, high quality analytical data could be acquired by improving sample pre-treatment techniques and/or ionization methods to increase ionization yields and/or avoid the generation of unwanted ions.

In the studies this thesis is based upon, a microfluidic electrocapture system capable of trapping charged proteins/polypeptides while non-charged species such as non-ionic detergents are swept out, was used to decrease the concentration of detergent in samples containing soluble and membrane associated proteins/polypeptide. Subsequent mass spectrometric analysis yielded well-resolved mass spectra of the target analytes.

In addition, it was found that solid phase extraction (SPE) sorbents such as graphitized carbon black (GCB), can efficiently assist the laser desorption ionization of small molecules without generating any interfering ions which inspired the fabrication of μ-traps and discs. Other matrix-free approaches demonstrated the utility of silicon nitride and oxidized GCB nanoparticles as versatile media for surface-assisted laser desorption ionization (SALDI) of small molecules.

In this thesis it is discussed that small molecule analytes such as Polyphenols present in red wine and quaternary protoberberine alkaloids with highly conjugated systems and acidic/permanently charged functional groups can be readily analyzed without any matrix or assisting-surface.

In summary, the microfluidic electrocapture, new laser desorption ionization methods and surfaces, as well as integrated SALDI and SPE platforms, introduced in this work extend the MS strategies allowing coverage of a wider range of samples.

Place, publisher, year, edition, pages
Stockholm: Department of Analytical Chemistry, Stockholm University, 2010. 77 p.
Keyword
Mass spectrometry, ESI-MS, SALDI-MS, Electrocapture, Sample treatment
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
Identifiers
urn:nbn:se:su:diva-32236 (URN)978-91-7155-981-4 (ISBN)
Public defence
2010-01-22, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: In PressAvailable from: 2009-12-17 Created: 2009-12-07 Last updated: 2011-08-31Bibliographically approved

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