Direct Coupling of HPTLC with MALDI-TOF MS for Qualitative Detection of Flavonoids on Phytochemical Fingerprints.
BACKGROUND
Thin layer chromatographic fingerprints of plant raw materials and extracts for food and pharma applications often focus on phenol carbonic acids and flavonoids. The visual detection and comparison of Rf values of applied reference substances only renders limited phytochemical information. Recently, direct coupling of TLC with MALDI-TOF MS has been successfully applied for analysis of biologically relevant compounds such as lipids. The mass analysis of low molecular weight TLC or HPTLC fingerprints of flavonoids has, to our knowledge, not yet been investigated.


OBJECTIVE
In this study, the feasibility of direct coupling of HPTLC with UV-MALDI-TOF MS for determination of molecular mass of the ubiquitously present flavonol glycoside, rutin, and flavone glycoside, luteolin-7-O-glucoside, as well as their corresponding aglycones, quercetin and luteolin, is demonstrated.


METHODS
HPTLC plate suitable for combination with a MALDI MS adapter was used for chromatographic separation of compounds of interest. After separation, the plate was sprayed with 2,5 dihydroxybenzoic acid as a MALDI matrix using an automated spraying device. After drying, the developed chromatograms were scanned by UV-MALDI-TOF MS in positive mode with a spatial resolution of 0.2 mm.


RESULTS
All compounds studied were distinctly detected in MALDI-TOF mass spectra. This is particularly pertinent for the co-eluted aglycones luteolin and quercetin, which could not have been distinguished by the common visual HPTLC derivatisation and evaluation.


CONCLUSIONS
This study demonstrates the potential of MALDI-TOF MS for the analysis of low molecular weight fingerprints of flavonoids directly from their HPTLC chromatogram. Copyright © 2016 John Wiley & Sons, Ltd.
Zurich University of Applied Sciences, Institute of Chemistry and Biotechnology, Einsiedlerstrasse 31, CH-8820, Wädenswil, Switzerland.
Ivana
I
Kroslakova
Zurich University of Applied Sciences, Institute of Chemistry and Biotechnology, Einsiedlerstrasse 31, CH-8820, Wädenswil, Switzerland.
Simona
S
Pedrussio
Zurich University of Applied Sciences, Institute of Chemistry and Biotechnology, Einsiedlerstrasse 31, CH-8820, Wädenswil, Switzerland.
Evelyn
E
Wolfram
D002855:Chromatography, Thin Layer / Q000379:methods*; D005240:Feasibility Studies; D047309:Flavones / Q000032:analysis*; D005419:Flavonoids / Q000032:analysis*; D044948:Flavonols / Q000032:analysis; D005960:Glucosides / Q000032:analysis*; D006027:Glycosides / Q000032:analysis*; D047311:Luteolin / Q000032:analysis; D064209:Phytochemicals / Q000032:analysis*; D011794:Quercetin / Q000032:analysis; D012431:Rutin / Q000032:analysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D047309:Flavones; D005419:Flavonoids; D044948:Flavonols; D005960:Glucosides; D006027:Glycosides; D064209:Phytochemicals; D012431:Rutin; C066408:luteolin-7-glucoside; D011794:Quercetin; D047311:Luteolin
HPTLC; MALDI-TOF MS; TLC; aglycones; coupling; fingerprint; flavonoids; glycosides