title: Characterization of condensed tannins and carbohydrates in hot water bark extracts of European softwood species.
abstract: Condensed tannins extracted from European softwood bark are recognized as alternatives to synthetic phenolics. The extraction is generally performed in hot water, leading to simultaneous extraction of other bark constituents such as carbohydrates, phenolic monomers and salts. Characterization of the extract's composition and identification of the extracted tannins' molecular structure are needed to better identify potential applications. Bark from Silver fir (Abies alba [Mill.]), European larch (Larix decidua [Mill.]), Norway spruce (Picea abies [Karst.]), Douglas fir (Pseudotsuga menziesii [Mirb.]) and Scots pine (Pinus sylvestris [L.]) were extracted in water at 60°C. The amounts of phenolic monomers, condensed tannins, carbohydrates, and inorganic compounds in the extract were determined. The molecular structures of condensed tannins and carbohydrates were also investigated (HPLC-UV combined with thiolysis, MALDI-TOF mass spectrometry, anion exchange chromatography). Distinct extract compositions and tannin structures were found in each of the analysed species. Procyanidins were the most ubiquitous tannins. The presence of phenolic glucosides in the tannin oligomers was suggested. Polysaccharides such as arabinans, arabinogalactans and glucans represented an important fraction of all extracts. Compared to traditionally used species (Mimosa and Quebracho) higher viscosities as well as faster chemical reactivities are expected in the analysed species. The most promising species for a bark tannin extraction was found to be larch, while the least encouraging results were detected in pine. A better knowledge of the interaction between the various extracted compounds is deemed an important matter for investigation in the context of industrial applications of such extracts.
authors.affiliation: Bern University of Applied Sciences, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel, Switzerland. Electronic address: sauro.bianchi@bfh.ch.
authors.forename: Sauro
authors.initials: S
authors.lastname: Bianchi
authors.affiliation: Zurich University of Applied Sciences, Institute of Chemistry and Biological Chemistry, Einsiedlerstrasse 31, 8820 Wädenswil, Switzerland.
authors.forename: Ivana
authors.initials: I
authors.lastname: Kroslakova
authors.affiliation: University of Hamburg, Department of Chemical Wood Technology, Leuschnerstraβe 91b, 21031 Hamburg, Germany.
authors.forename: Ron
authors.initials: R
authors.lastname: Janzon
authors.affiliation: Bern University of Applied Sciences, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel, Switzerland.
authors.forename: Ingo
authors.initials: I
authors.lastname: Mayer
authors.affiliation: University of Hamburg, Department of Chemical Wood Technology, Leuschnerstraβe 91b, 21031 Hamburg, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Saake
authors.affiliation: Bern University of Applied Sciences, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel, Switzerland.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pichelin
mesh_terms: D044946:Biflavonoids; D002392:Catechin; D002851:Chromatography, High Pressure Liquid; D005419:Flavonoids; D005960:Glucosides / Q000737:chemistry; D006358:Hot Temperature; D015394:Molecular Structure; D009664:Norway; D028222:Picea / Q000737:chemistry*; D028223:Pinus; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry; D044945:Proanthocyanidins; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013634:Tannins / Q000737:chemistry / Q000302:isolation & purification*; D014867:Water / Q000378:metabolism*
chemical_list: D044946:Biflavonoids; D005419:Flavonoids; D005960:Glucosides; D010936:Plant Extracts; D044945:Proanthocyanidins; D013634:Tannins; D014867:Water; C017674:procyanidin; C024070:pycnogenols; D002392:Catechin
keywords: Abies alba; Carbohydrates; Condensed tannins; Larix decidua; MALDI-TOF MS; Picea abies; Pinus sylvestris; Pseudotsuga menziesii; Softwood bark extracts; Thiolysis