Analysis of the structure of condensed tannins in water extracts from bark tissues of Norway spruce (Picea abies [Karst.]) and Silver fir (Abies alba [Mill.]) using MALDI-TOF mass spectrometry.

Condensed tannins extracted from the bark of softwoods have been proven to be suitable compoundsin the formulation of environmentally friendly adhesives and resins. Their chemical structure has beenshown to significantly influence their properties and possible applications. Condensed tannins extractedfrom the bark of Norway spruce (Picea abies [Karst.]) and Silver fir (Abies alba [Mill.]) still lack a detailcharacterization of their chemical structure.In an effort to address this deficiency, barks from these species were collected and extracted in water at60◦C. The dried extracts were analyzed by MALDI-TOF mass spectrometry to identify the building blocksand to determine the degree of polymerization of the tannin oligomers. The condensed tannins extractedfrom spruce bark at the used conditions were mainly composed of procyanidins with a polymerizationdegree up to 13. Silver fir extracts revealed a predominance of prodelphinidins with a polymerizationdegree up to 9. The presence of less common building blocks such as stilbene glucosides and flavan-3-ols gallates was also hinted. Different curing times and viscosities in resin formulations are expectedbetween the two studied species, as well as in comparison to the most known and available tannins fromtropical species.