MALDI-TOF and 13C NMR characterization of maritime pine industrial tannin extract

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is a suitable method for examining polyflavonoid tannin oligomers as it is capable to determine aspects of their oligomeric structure and characteristics, which are otherwise too difficult to determine by other techniques. It has been possible to determine by MALDI-TOF for non-purified industrially extracted maritime pine polyflavonoid tannin that: (i) procyanidins oligomers formed by catechin/epicatechin, epigallocatechin and epicatechin gallate monomers are present in the tannin. The presence of epicatechin gallate and of the other structures has been confirmed by 13C NMR; (ii) oligomers up to 20–21 repeating monoflavonoid units in which the repeating unit at 528–529 Da is a catechin gallate dimer that has lost both the gallic acid residues and a hydroxygroup are the predominant species, all procyanidin-related; (iii) oligomers of the two types covalently linked to each other also occur; (iv) small proportion of fisetinidin units also appear to be present in this tannin fisetinidin.