STRUCTURE OF FRUCTAN POLYMERS FROM TUBEROUS ROOTS OF GOMPHRENA MACROCEPHALA (AMARANTHACEAE) FROM THE CERRADO

Two fructo-polysaccharides, FP-I and FP-II, were separated from a solu ble extract from tuberous roots of Gomphrena macrocephala St.-Hil. by gel permeation chromatography on Toyopearl HW-40S, FP-I and FP-II were mixtures of saccharides with a wide-ranging degree of polymerization; their acid hydrolysis products were fructose and glucose. The ratios of fructose to glucose in the hydrolysates of FP-I and FP-II were 38 a nd 60, respectively. The average molecular weights of FP-I and FP-II w ere estimated to be 5500 and 10000 respectively, by gel permeation HPL C. The structural confirmation of FP-I and FP-II was made by C-13-NMR analysis. Intense signals corresponding to carbon-1 (C1), C2, C3, C4, C5 and C6 of fructose residues in FP-I and FP-II were observed at delt a 60.60, 104.93, 76.99, 75.91, 81.02 and 64.11, respectively. These ch emical shifts coincided with those of timothy and bacterial levans. Th e less intense resonances were tentatively assigned to carbons of term inal fructosyl residues and a fructosyl residue linked to a glucose re sidue by a beta-2,1 bond in FP-I and FP-II. Also, weak signals attribu ted to carbons of the glucose residue in both polysaccharides were sep arated from those of other glycosyl residues. These findings were supp orted by GLC analysis of methanolysate from permethylated FP-I and FP- II. Thus FP-I and FP-II comprise fructose residues with beta-2,6 linka ges, and a terminal glucose bound with fructose residues at position C 1, although both polysaccharides possibly contained a non-terminal glu cose residue in the molecule.