Soluble lignin-carbohydrate complexes from sheep rumen fluid: their composition and structural features.

Lignin-carbohydrate complexes, isolated from cell-free rumen fluid of sheep, consisted of polyphenolic material in association with carbohydrate (5.5%) and protein (1.8%). No separation of carbohydrate from the other components could be effected. The complexes showed a bimodal distribution of molecular size with the higher-molecular-weight fraction richer in carbohydrate. Methylation analysis indicated a wide range of linkages and a high proportion of terminal sugars. Reducing sugars were found in the complexes, particularly in the low-molecular-weight fraction (approximately 25%), suggesting that ether linkages to the phenolics were also present.