Determination of Molecular Structures of Condensed Tannins from Plant Tissues Using HPLC-UV Combined with Thiolysis and MALDI-TOF Mass Spectrometry.

Condensed tannins extracted from plant tissues are suitable substitutes for phenolic resins.
Their molecular structure, which might influence their chemical reactivity, can be assessed by the use
of both HPLC-UV after acid thiolysis and MALDI-TOF mass spectrometry. Thiolysis of plant extracts in
acidic methanol with cysteamine hydrochloride results in the release of the monomeric units of the
condensed tannin oligomers that can be further quantified by reversed-phase HPLC-UV by comparison
with analytical standards. MALDI-TOF mass spectrometry using 2,5-dihydroxybenzoic acid as matrix
and K+ as cationization agent highlights the molecular structural characteristics (e.g., monomeric unit
sequence) of the tannin oligomers. The methodologies permit the estimation of the mean and the
maximum (observable) degree of polymerization, the type of monomeric units and the presence of
glycosylation and/or esterification of the tannin oligomers.