Abstract
Flaxseed gum (FSG) is a heteropolysaccharide consist of neutral and acidic components that makes up approximately 8% of seed mass. FSG was extracted from mixture of brown and golden varieties of flaxseeds by hot water extraction method. The molecular weight distribution, monosaccharide analysis, chemical composition, and surface morphology of FSG were scrutinized in the current study to get a better insight regarding this important polysaccharide. The average molecular weight was recorded as 1,322 kDa with a polydispersity ratio of 1.6 for Mw/Mn and 2.4 for Mn/Mz. High-performance liquid chromatography (HPLC) screening revealed that extracted FSG was comprised of rhamnose, arabinose, mannose, glucose, fucose, xylose, galactose, glucosamine, glucuronic acid, and galacturonic acid, of which mannose and glucosamine have not been reported previously. The antioxidant activities of FSG measured as DPPH, ABTS, reducing power, and total antioxidant activity clearly demonstrated the antioxidant potency of FSG. Fourier-transform infrared spectroscopy (FTIR) and the Nuclear magnetic resonance (NMR) (1 H, 13 C) spectra ratified the presence of functional groups typical for polysaccharide. PRACTICAL APPLICATIONS: Flaxseed gum is a natural carbohydrate polymar. This study provides useful information regarding antioxidant potential, chemical, and structural characterization of FSG. The availability of a gum is fully characterized with bioactive composition, structural features, and antioxidant potential provides a toolset for the practical application in the food or drug industry.
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Key Points
Flaxseed contains a polysaccharide gum confined to the region of the outer layer of flaxseed shell (approx. 8% of the seed weight). Water‐soluble flaxseed polysaccharides commonly referred to as flaxseed gum (FSG) can be easily released upon soaking the seeds in water. FSG is a heterogeneous polysaccharide that comprises of two polysaccharide constituents, a neutral arabinoxylan (75%) including l‐arabinose, d‐xylose, and d‐galactose and the acidic rhamnogalacturonan (25%) containing l‐rhamnose, l‐fucose, l‐galactose, and d‐galacturonic acid. In the current study, the structural characterization of FSG was determined. FSG exhibited remarkable monosaccharide composition, antioxidant potential and structural features. FSG with low molecular weight (1,322 kDa) exhibited significantly higher antioxidant activity values at higher concentration up to 30 mg/ml, while there were significant differences in terms of values or units among DPPH, ABTS, reducing power, and TAC and showing the extracted FSG as an interesting natural antioxidant molecule.