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Soluble lignin complexes isolated from wheat straw ( Triticum arvense ) and red clover ( Trifolium pratense ) stems by an in‐vitro method
Author(s) -
Nordkvist Erik,
Graham Hadden,
Åman Per
Publication year - 1989
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740480307
Subject(s) - red clover , chemistry , lignin , straw , rumen , xylose , avena , chromatography , food science , botany , biology , organic chemistry , fermentation , inorganic chemistry
Soluble degraded lignin complexes (LCs) were prepared using a two‐step incubation with buffered rumen fluid, and isolation of the LC from the latter liquid phase by filtration, dialysis and freeze drying. The yields of crude LC were 19 and 10 g kg −1 of initial dry matter for wheat straw ( Triticum arvense L cv Holme) and red clover ( Trifolium pratense L cv Hermes II) stems, respectively. Gel permeation chromatography of both LCs showed similar patterns with about 95% of the material having a molecular weight of 12 000 to 16 000 when compared with dextran standards. The total content of carbohydrates in the complexes was 82 g kg −1 DM in wheat straw LC and 50 g kg −1 DM in red clover stem LC. Uronic acid and arabinose residues dominated both species with xylose, galactose and glucose as important residues in wheat straw LC and galactose and glucose residues in red clover stem LC. The lignin content estimated by the acetyl bromide method was 328 g kg −1 DM in wheat straw LC and 139 g kg −1 DM in red clover stem LC, and nitrobenzene oxidation of both LCs yielded vanillin and syringic aldehyde in approximately equal amounts. NMR spectroscopy gave glycosidic, but not aromatic, signals, and ESR spectroscopy indicated the presence of stable radicals.