An arabinogalactan from flowers of Chrysanthemum morifolium: structural and bioactivity studies

Abstract

A water-soluble polysaccharide (P2) with a molecular weight of 1.7×105Da was isolated from the hot aqueous extract of flowers of the Chrysanthemum morifolium. It was homogeneous for there was only a symmetrical peak on the spectrum of high-performance gel permeation chromatography. Monosaccharide analysis revealed that P2 is an arabinogalactan containing arabinose (38.4% w/w), galactose (58.8% w/w), and glucose (2.8% w/w) in a ratio of 1:1.53:0.07. The GC–MS results of the derived alditol acetates from the permethylated P2 showed some separate peaks corresponding to (1→6)-linked Gal, (1→3,6)-linked Gal, terminal Ara, (1→5)-linked Ara, and (1→3,5)-linked Ara units in a molar ratio of nearly 1.12:1.90:1.84:0.35:0.12. Terminal Glc unit also existed in a trace amount. 1H, 13C, DEPT-135 and 2D NMR (including HMQC and HMBC), as well as graded acid hydrolysis experiment, indicated that the core structure features include a backbone chain consisting of (1→6)-linked and (1→3,6)-linked Galp residues. Side chains which were composed of terminal Glcp, terminal, (1→5)-linked and (1→3,5)-linked Araf residues were located at position 3. Additionally, P2 showed good immunological activity as it significantly enhanced splenocyte proliferation in relatively low 25 and 50μg/mL doses. However, P2 showed little effects of thymocyte proliferation, indicating that it may have two modes of action.