Isolation and structural analysis of new fructans produced by chicory

This report describes a new series of oligosaccharides, which is formed in chicory roots under forcing conditions and during in vitro experiments using purified chicory 1-FFT (fructan:fructan 1-fructosyl transferase). It was demonstrated that the three smallest members of this new series (disaccharide, trisaccharide and tetrasaccharide) contain exclusively beta -D-fructosyl residues after hydrolysis. The present data demonstrate that the smallest compound is levan-biose and that the other oligomers of this new series of fructans do not belong to the linear 2 -->6 linked levan-oligosaccharides nor to the linear 2 -->1 linked inulo-oligosaccharides. A combination of several chromatographic techniques yielded a fraction that contained only the compound with degree of polymerisation (DP) 2 (levanbiose, beta -D-fructofuranosyl-(2 -->6)-D-fructofuranose), and a mixture of DP 3 of the new series and 1-kestose. Using homonuclear and heteronuclear 2D NMR experiments the complete H-1 and C-13 NMR assignments of levanbiose and DP 3 were obtained. From High Performance Anion Exchange Chromatography (HPAEC) and NMR experiments of DP 3 of the new series it was concluded that the molecule contains a beta -D-fructofuranosyl residue 2 -->1 linked to the non-reducing moiety of levanbiose, and thus has to be named beta -D-fructofuranosyl-(2 -->1)-beta -D-fructofuranosyl-(2 -->6)-D-fructofuranose The simple and regular pattern of the HPAEC retention times of the new oligosaccharides suggests that it is a homologous series of oligomers build by 2 -->1 elongation with beta -D-fructofuranosyl residues at the non-reducing residue of levanbiose.