Isolation, purification, structural analysis and in vitro activity of polysaccharides from Amelanchier alnifolia Nutt.

Amelanchier alnifolia polysaccharides (AAP) were isolated and purified and gave three sequential fractions, AAP1, AAP2 and AAP3. AAP3 was further separated and purified by cellulose chromatography to give three polysaccharide fractions, AAP3-I, AAP3-II and AAP3-III. A polysaccharide (AAP3-Ⅰ) with a molecular weight of 1.64 × 106 Da was mainly composed of rhamnose, glucose, galactose, xylose and arabinose. The Fourier transform infrared spectroscopy (FT-IR) analysis and DEAE-Cellulose-52 column elution results indicated that AAP3-Ⅰ is a neutral polysaccharide. The transmission electron microscopy (TEM) indicated that purified polysaccharide molecules are of higher purity and are in reticulated aggregates. AAP3-I exists in an entangled triple helix conformation. In vitro antioxidant assays showed that all three fractions had good, concentration-dependent, antioxidant properties. The antioxidant capacity was in the order AAP1 < AAP2 < AAP3. Therefore, AAP3 could serve as a potential natural antioxidant to prevent aging.