Extraction, purification and characterization of water-soluble polysaccharides from green walnut husk with anti-oxidant and anti-proliferative capacities

This work was designed to study the physicochemical properties, and bioactivity of green walnut husk polysaccharides (GWHP). The crude GWHP was fractionated into three fractions, namely, GWHP-1, GWHP-2 and GWHP-3, using Cellulose DEAE-52 and Sephadex G-150. HPLC analysis showed that the three fractions were heteropolysaccharides consisting primarily of glucose, galactose and arabinose with average molecular weights of 165.06, 179.64 and 255.75 kDa, respectively, and that the monosaccharide composition of GWHP-1 was more complicated than those of GWHP-2 and GWHP-3. The primary structures of the GWHP fractions were similar to each other. GWHP-1, obtained from water elution, showed higher anti-oxidant activities in the tested concentration range of 0.1-1.8 mg/mL than did GWHP-2 and GWHP-3, which were obtained by elution with 0.1 M and 0.2 M NaCl solutions. Additionally, the GWHP-1 fraction showed the most effective anti-proliferative activity among the three fractions, which was associated with the weakened cell proliferation and increased lactate dehydrogenase (LDH) leakage of LoVo cells. However, GWHP-1 displayed a lower growth inhibition effect on colonic NCM640 cells, which was characterized by low LDH leakage. The above results indicated that the polysaccharides, especially GWHP-1, may be a valuable natural anti-oxidant and anti-cancer cell source for applications in the pharmaceutical and food industries.