Maldi-ToF analysis and FTIR characterization of Aucoumea klaineana Pierre (Okoume) sapwood and heartwood condensed tannins from Gabon’s natural forest

Aucoumea klaineana Pierre (Okoume) tannins were extracted by an artisanal maceration method in the presence of acetone/water used as solvent. The tannins obtained from the sapwood and heartwood and characterized by Maldi-ToF and FTIR did not present any differences regarding their type of oligomers. Tannins were more abundant in sapwood than in heartwood, but in both of them, fisetinidin and gallocatechin were the main monomers of condensed tannin. A low content of trihydroxyflavan monomer was identified, whereas non-glycosylated condensed tannins up to seven oligomers were found in high content in Okoume. These results, which revealed for the first time the chemical structure of Okoume condensed tannins showed the presence of a glycosylated condensed tannin series up to six carbohydrate residues attached to 2xgallocatechin-1xcatechin flavonoids.