Characterization of an arabinogalactan-protein isolated from pressed juiceof Echinacea purpurea by precipitation with the beta-glucosyl Yariv reagent

An arabinogalactan-protein (AGP) from pressed juice of Echinacea purpurea h erb was isolated from a high molecular weight fraction by precipitation wit h the beta-glucosyl Yariv reagent, followed by gel-permeation chromatograph y. It revealed characteristic features of other AGPs: i.e., a high amount o f polysaccharide (83%) with a ratio of galactose to arabinose of 1.8:1, som e uronic acids (4-5%), and a low protein content (7%) with high levels of s erine, alanine and hydroxyproline. The molecular weight was estimated to be 1.2 x 10(6) Da. Linkage and C-13 NMR analyses showed that the AGP is compo sed of a highly branched core polysaccharide of 3-, 6-, and 3,6-linked Galp residues with terminal Araf, GlcAp and terminal units of Araf-(1 --> 5)-Ar af-(1 -->. Partial acid hydrolysis resulted in loss of Araf residues at the periphery of the molecule. Complete loss of reactivity toward the beta-glu cosyl Yariv antigen was then noticed. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.