Characterization of Pinus brutia bark tannin by MALDI-TOF MS and 13C NMR

•The water extract of Pinus brutia bark was investigated by MALDI-TOF MS.•The fractions dissolved by ethyl acetate and 98% acetone were analyzed by GC–MS. Solid and liquid 13C NMR spectra were taken.•Taxifolin was the predominant flavanoid monomer and constituted about 10% of the extract.•The brutia bark tannin oligomers consisted mainly of catechin units, gallocatechin and of some glycosidic and esterified flavan-3-ols. The structures of condensed tannin from Pinus brutia bark were characterized by means of GC–MS, solid and liquid state 13C NMR and MALDI-TOF MS analyses. The results indicated that the monomeric units building up the condensed tannin of brutia pine bark are mainly composed of catechin/epicatechin, gallocatechin/epigallocatechin units accompanied by possibly tri- or tetra hydroxyl-flavanols. Some oligomers appear to present p-hydroxy- or 3,4-dihydroxy benzoic acid residues or glucose at their terminal unit. Apart from oligomers, monomeric flavanoids were also present in the brutia bark extract. Taxifolin was especially found in appreciable amounts. Additionally, in this tannin procyanidin oligomers predominated while prodelphinidin units were present to a lesser extent. The NMR results showed that the oligomers in brutia pine bark tannin Exhibit 2,3-cis stereochemistry and C4–C6 bonds with a noticeable portion of C4–C8 interflavonoid links being present. The MALDI-TOF MS showed a series of peaks corresponding to flavonoid hexamers of the condensed tannin (1750Da).