A comparative study of the neutral and acidic polysaccharides from Allium macrostemon Bunge

Neutral and acidic polysaccharides, named AMP40N and AMP40S respectively, were isolated and purified from the dried bulbs of Allium macrostemon Bunge. Both of them showed a single and symmetrically sharp peak, indicating they were homogeneous polysaccharides. Molecular weights of AMP40N and AMP40S were determined to be 18.2 and 105.1 kDa, respectively. AMP40N was composed of arabinose and glucose, while AMP40S was composed of rhamnose, arabinose, glucose and galactose and a certain amount of uronic acid. FT-IR, periodic acid oxidation, Smith degradation, methylation and GC-MS analysis revealed that non-reducing terminal and →2,6)-Glc-(1→ existed in AMP40N and AMP40S. The glycosidic linkage of arabinose in AMP40N was →2)-Ara-(1→, whereas it was Ara-(1→ in AMP40S. AMP40S had (1→2)-linked l-rhamnose residue. Both AMP40N and AMP40S exhibited strong anti-tumor potential against human gastric carcinoma cells BGC-823, in particular, AMP40S presented significantly higher inhibitory rate of 85.94% than AMP40N of 52.63%.