Qualitative Analysis of Polyphenols

If you are good at solving puzzles, then perhaps you could shine also with the qualitative analysis of polyphenols: this is a multi-step process where you must master many separate analysis techniques

nmrSimilarly to polyphenol purification their characterization or identification by qualitative analysis is a prerequisite to understanding their biological functions. Luckily the evolution of chromatographic techniques hand-in-hand with mass spectrometry has enabled quite efficient characterization of different types of polyphenols even from complex mixtures.

We currently characterize our polyphenols first by HPLC-DAD-QTOF-MS and/or by UPLC-DAD-QQQ-MS. These enable us to classify individual polyphenols into specific sub-groups and in many cases the structures can be elucidated quite accurately even with these methods only. Naturally our library of reference compounds helps in this task together with the years of experience in interpreting the UV, MS and MS/MS spectra.

mrmIt makes sense to purify polyphenols if their structures remain unresolved by the above mentioned techniques. For purification purposes gel chromatography followed by preparative and semi-preparative LC is typically sufficient to achieve pure polyphenols. For some of the largest tannins even these techniques are not sufficient to isolate them as individual compounds. In these special cases new methods need to be created or the largest tannins isolated as mixtures instead of individuals.

If and when some of the isolated structures need to be verified by the use of one- or two-dimensinal NMR techniques, we have experts and facilities for this task as well. Especially the complicated tannin structures are such that they cannot be fully identified without the extensive NMR investigations perhaps accompanied by analyte modifications that make the NMR spectra simpler to interpret.

Our flag publication in this front is the recent ellagitannin characterization paper by Johanna:

Moilanen, J.; Sinkkonen, J.; Salminen, J.-P. 2013. Characterization of bioactive plant ellagitannins by chromatographic, spectroscopic and mass spectrometric methods. Chemoecology 23(3): 165–179.