MALDI-TOF Analysis of Aleppo Pine (Pinus halepensis) Bark Tannin

Abstract

Matrix-assisted laser desorption/ionisation time of flight (MALDI-TOF) mass spectrometry is a suitable method for examining polyflavonoid tannin oligomers because it has the capability to determine aspects of their oligomeric structure and characteristics that are too difficult to determine by other techniques. For non-purified industrially extracted Aleppo pine polyflavonoid tannin, it was possible to determine by MALDI-TOF that: (i) oligomers formed by catechin/epicatechin are present in tannin, as are mixed oligomer units with fisetinidin and robinetinidin units; the presence of flavonoid gallate and other structures was confirmed; (ii) oligomers up to 12 to 13 repeating monoflavonoid units, in which the repeating unit is at 264 Da, have been confirmed; and (iii) oligomers of the two types covalently linked to each other also occur. The presence of a small proportion of hydrolysable tannins by chemical analysis can also be explained by gallate residues attached to some of the flavonoid oligomers.