Extracellular polysaccharides produced by tuberose callus

Abstract A high yield of extracellular polysaccharide (ECP) was obtained from callus cultures of tuberose ( Polianthes tuberosa ), which could be separated into an unadsorbed and two acidic fractions (TPS-1, -2) by ion-exchange column chromatography. The yields of each fraction were markedly increased by the addition of 10 −5 M 2,4-dichlorophenoxyacetic acid to the medium. Of the three fractions, the amount of TPS-1 accounted for over 60% of total yield of ECP, which was a predominant polysaccharide consisting of arabinose (Ara), mannose (Man) and galactose (Gal) as major neutral monosaccharides. Judging from the patterns of electrophoresis and ultra-centrifugation, TPS-1 was identified to be homogeneous. Methylation and GC-mass spectrometry analyses of this fraction revealed the presence of 1,2,3-linked Man, 1-linked Ara, 1,3-linked Ara, 1-linked Gal and 1,3,4-linked glucuronosyl (GlcUA) residues in a molar ratio of 1.0:1.08:0.85:0.75:1.08. Based on additional analyses of the mild acid hydrolysate and the absolute configuration of the constituent monosaccharides, a possible structure for TPS-1 was a glucuronomannan possessing the unit of → 4)-β- d - GlcUA p-(1 → 2)-α- d - Man p-(1 → with branching at the C-3 position, where → 1)-α- l - Ara f , → 1)-α- d - gal p , → 1)-α- l - Ara f-(3 → 1)-α- l - Ara f or → 1)-α- l - Ara f-(3 → 1)-β- d - Gal p were attached randomly. About 35% of the GlcUA moieties were present as methyl esters. Further confirmation was made 1 H and 13 C NMR spectroscopy.