Structural Characterization And Immunologic Enhancement Of Polysaccharide Isolated From The Stem Of Physalis Alkekengi L .

Physalis alkekengi L. is a traditional Chinese herbal plant. The broad use of this plant in popular medicine includes anti-inflammatory, anti-cold, anti-cough and anti-fungal activities. Some active components from P. alkekengi such as physalin, alkaloids, and flavone have been investigated. We have previously reported adjuvant and hypoglycemic activities of polysaccharide isolated from fruits of P. alkekengi. However, no specific studies on the immunologic enhancement of the water-soluble polysaccharide (designated WSP below), which was isolated from the stem of P. alkekengi, have been carried out. We therefore specifically focused on purification and structural characterization of WSP and immunological enhancement of WSP.In this papar: The water-soluble crude polysaccharide isolated from the stem of Physalis alkekengi L. by hot water extraction, ethanol precipitation and removed protein, was fractionated by QAE Sephadex A-25 gel filtration chromatography and high performance lquid chromatography, giving the WSP. HPLC indicated that molecular weight of 7kDa. According to GC analysis, WSP was composed of Rha,Ara,Gal,Glc,GalA and trace galacturonic acid with molar ratios of 2.6:1.0:6.5:3.5:2.4. The structural characteristics of WSP were investigated by methylation analysis, CMC-esterification-reduction, periodate oxidation, Smith degradation, partial acid hydrolysis and IR analysis. It has a backbone composed of (1→3) - linked Gal, (1→2) - linked Ara and (1→3) - linked GalA with branches composed of (1→2) - linked Rha, (1→3) - linked Glc, (1→3) - linked GalA, and terminated with Gal and GalA.To detect the immunologic enhancement of WSP, the male ICR mice were immunized subcutaneously with OVA alone, or with OVA containing QuilA or WSP twice at 14-day interval. The mice were sacrificed two weeks after the last immunization to analyze antibody titers in serum by ELISA. The results indicated that WSP at dose of 200μg substantially enhanced OVA-specific IgG level in OVA-immunized mice, which was as effective as that of QuilA.