Reproducible Ethanol-Induced Precipitation and Systematic Characterization of an α-D-Glucopyranose-Rich Solid from Khalas Date Fruit (Phoenix dactylifera L.)

In an attempt to prepare ethanolic extracts of date fruit (Phoenix dactylifera L.) from the Khalas variety, a white solid precipitate was reproducibly obtained from three independent batches. A systematic analytical approach established that the isolated solid consisted predominantly of α-D-glucopyranose together with a small amount of D-fructose. TLC indicated monosaccharide behavior, LC–MS confirmed the presence of hexose species, and NMR spectroscopy established α-D-glucopyranose as the predominant component while providing spectroscopic support for a minor D-fructose component. Following identification of these two hexoses, polarimetric analysis based on their opposite specific rotations yielded an estimated composition of 93.8% D-glucose and 6.2% D-fructose under the applied binary glucose–fructose model. The α-anomeric proton (H-1) appeared as a doublet at δ 5.20 ppm (J = 3.5 Hz), consistent with an axial–equatorial relationship between H-1 and H-2. Mutarotation in aqueous solution shifted the equilibrium toward the thermodynamically more stable β-anomer, as evidenced by the decrease in the relative integral of the α-anomeric doublet at δ 5.20 ppm and the corresponding increase in the β-anomeric doublet at δ 4.62 ppm (J = 8.0 Hz), consistent with a diaxial relationship between H-1 and H-2. The present findings demonstrate the reproducible direct ethanol-induced isolation of an α-D-glucopyranose-rich solid from Khalas date fruit without prior aqueous extraction, together with anomer-specific characterization of the isolated material and its subsequent mutarotation in aqueous solution.