Effects Of Superfine Grinding On Yield Rate And Physicochemical Properties Of Polysaccharides From Lycium Barbarum L.

Lycium barbarum L. is used as our traditional food and the precious traditional Chinese medicine. It possesses many kinds of pharmacological and physiological activities, which has great relations with Lycium barbarum polysaccharide (LBP). However, due to the processing characteristics of LBP and its mechanism was not clear, the development and utilization of LBP were affected. Ningxia wolfberry was used as raw materials of the topics. The conventional and superfine grinding assistant extraction conditions for LBP were established. The effects of superfine grinding treatment on extraction yield rate, physicochemical properties and antioxidant activities of LBP were also investigated. The main results are as follows:In the experiment, with the extraction yield rate as an indicator, the extracting parameters were optimized by orthogonal analysis and response surface analysis on the basis of single factor experiments. Results showed that the conventional water extraction and superfine grinding extraction gave polysaccharides yield rate of 3.46% and 4.00%, respectively.The coarse LBP was classified using ethanol fractional precipitation method. And the molecular weights of LBP conjugate fractions were determined by high performance liquid chromatography (HPLC). The results showed that ethanol fractional precipitation method had certain effect on the classification purification of LBP. And superfine grinding treatments could decrease the average molecular weights of LBP fractions (changed from 834.0,1786.2,1172.8,900.8 and 72.2 kDa to 538.4,1386.1,746.5,288.2 and 2.1 kDa, respectively).The physicochemical properties (chemical composition, morphological properties, thermodynamic properties) were comparatively investigated by chemical methods, gel permeation chromatography (GC), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). After superfine grinding treated, the protein contents of LBP changed from 2.36%,2.30%,2.89%,1.91% and 2.15% to 2.32%,1.56%,1.86%,1.30% and 0.69%, respectively. Superfine grinding treatment could decrease the spherical particle’s heights and the spherical particle’s diameter of LBP. All the LBP fractions were composed of the same monosaccharide composition. However, the molar content of the monosaccharide was quite different from LBP fractions. There was no significant difference observed by DSC between LBP fractions from superfine grinding treated and untreated material, suggesting that superfine grinding treatment had no significant influence on thermodynamic properties of LBP.The antioxidant properties were determined using DPPH, ABTS free radical assay and the FRAP ability. The IC50 of LBP from treated materials on DPPH radical (4.96,6.16,2.55, 1.98 and 2.97 mg/mL) and ABTS radical (2.25,2.51,0.39,0.20 and 0.25 mg/mL) were extremely lower than those of LBP from untreated materials. Under the same concentration, the FRAP ability of LBP from treated materials was even stronger than those of LBP from untreated materials.In conclusion, the results suggested that superfine grinding treatment could effectively decrease the average molecular weights and enhance the antioxidant activities of LBP. The antioxidant activities of LBP were related to the molecular weight and solution behavior of LBP. Namely, in a certain range, polysaccharides with lower molecular weight showed stronger antioxidant activity. However, when the molecular weight was too low, polysaccharide molecules in solution intended to congregate, the probability for it to take part in oxidation-reduction reaction area would decrease, and its antioxidant activity weakened.