Isolation and Characterization of Anticomplementary β-Glucans from the Shoots of Bamboo Phyllostachys edulis

Abstract

Bamboo, Phyllostachys edulis produces well known edible shoots in Asia. Immunostimulating anticomplementary (complement activating) substances have been recognized as a characteristic biological response modifier (BRM). In the present study, we isolated and characterized three anticomplementary β-glucans (BS-BGA, BS-BGB, and BS-BGC) from bamboo shoots. Hot-water extraction, DEAE-Toyopearl 650M-column chromatography, amylase digestion and concanavalin A adsorption, and Sephacryl S-100 HR column chromatography were applied to isolate the β-glucans. The average molecular masses of the β-glucans were estimated to be from 14,500 to 85,300 Da by HPSEC-MALLS-RI. All three β-glucans (0.1 - 1.0 mg/mL) activated the complement system via the alternative pathway, and could cleave human complement C3 under Ca²⁺-free gelatin veronal buffered saline. Among them, the largest molecule, BS-BGA was the most potent complement activator. Methylation analysis and NMR spectroscopy were used to achieve their structural characterization. They are all water-soluble and composed mainly of backbone structures of β-(1→3)-glucan with β-(1→4)-linked side chains varying in degree of branching. BS-BGA consisted of a higher proportion of 3-linked glucopyranosyl residues and a lower degree of branching than BS-BGB and BS-BGC. In particular, BS-BGA contained a small amount of O-acetyl groups at C-6 of the 3-linked glucopyranosyl residues. These data demonstrate that the structural characteristics including molecular size, degree of branching, and O-acetyl substitution are involved, at least in part, in their different anticomplementary activities.

Key words

Phyllostachys edulis shoots - Poaceae - anticomplementary activity - C3 - water-soluble β-glucan

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