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A galactomannan was obtained from mature seeds of
Dimorphandra gardneriana Tul., the plant from which rutin is extracted. The galactomannan extraction was based on manual separation of the endosperm, water dissolution, centrifugation and precipitation with ethanol. The galactomannan yield obtained (31%) was similar to values reported for other Brazilian seeds and to that of guar gum. The polysaccharide from
D. gardneriana seeds (GalDG) was characterized by gas–liquid chromatography (GLC), gel permeation chromatography (GPC), rheology and also by
13C and
1H nuclear magnetic resonance (NMR). The monosaccharide composition in weight % was mannose 64.2, galactose 34.7 and glucose 1.1. Small amounts of protein and uronic acid were found, values being 1.75 and 2.8% (w/w), respectively. The mannose/galactose ratio of GalDG (1.84) is similar to values reported for galactomannans extracted from other Brazilian seeds, and is the M/G value closest to that of guar gum (1.6–1.8). The intrinsic viscosity of galactomannan from
D. gardneriana (8.7
dL/g), in water at 25
°C, is lower than the [
η] value of guar gum, but the absolute viscosity of the GalDG in aqueous solution at concentrations of 0.1 and 1% (w/v) is higher. The aqueous solution at 1% (w/v) behaves as a pseudoplastic fluid, but a Newtonian behavior was noted for the solution at 0.1%. The high average molar masses,
M
w of 3.9
×
10
7
g/mol and
M
n of 1.9
×
10
7
g/mol, determined by GPC are probably due to molecular aggregation.
13C and
1H NMR spectra (DEPT 135 and HSQC) of GalDG solutions in D
2O were recorded. The patterns of mannose substitution in GalDG and guar gum are similar.