Screening And Structure Analysis Of Platycodon Grandiflorum Antioxidant Functional Polysaccharides

Platycodon grandiflorum(Jacq.)A.DC. is the dried root of this herbaceous plant which belongs to the Campanulaceae family. It is the primary component and played an irreplaceable role in the national new prescription “Qinbaiqingfei pellets” which is modified from the classic prescription “Zhisou Powder”. The platycodins has always been the hotspot research in the pharmacology of “eliminating evil” of P. grandiflorum, while this research is emphasized on the polysaccharides which are largely existing in it. In this research, polysaccharides isolated from P. grandiflorum were screened by the inhibition test of Mycoplasma pneumoniae and antioxidant test in vitro. The Polysaccharide fragment marked as PGP-D which showed greater activity was obtained. Then purification and structure analysis of PGP-D were further made in order to optimize the dosage form and supply theoretical basis of structure-function relationship.Firstly, the P. grandiflorum cultivated in Huizhou of Anhui Province was selected by the index of polysaccharides content. The polysaccharides of P. grandiflorum were extracted by hot water reflux and the extraction condition of polysaccharides was optimized to determine the optimum process parameters by response surface analysis. The optimum extraction condition was as follows: extraction temperature of 92.76℃, extraction time of 2.45 h, water to material ratio at 1:31.41 and extract for 2.82 times, the extraction yield of polysaccharides could reach 50.23%. The practical extraction parameters were recommended as extraction temperature of 93℃, extraction time of 2.45 h, water to material ratio at 1:31 and extracting for 3 times, the extraction yield of polysaccharides could reach 49.85%.The Sevage method was used in deproteinization and the removal times were studied. The removal rate of protein could reach 28.49% and the retention rate of polysaccharide was 81.16% after deproteinizing two times. Finally the protein content of P. grandiflorum remained only of 0.05%. Multiple comparison among three decolorization methods were performed. The result showed that the active carbon exhibited the worst effect which can hardly decolorize; the AB-8 resin exhibited the best effect that the decolorization rate could reach 75% when the polysaccharide solution was 7 times of column volume; and the decolorization effect of H2O2 is inferior to the AB-8 resin, which decolorization rate was 5% when the amount of its addition was 69.42%.P. grandiflorum fractions(PGP-B, PGP-C and PGP-D) were obtained by ethanol fractionation with polysaccharide contents of 73.33%, 72.45% and 80.83% respectively. The intrinsic viscosity[η] and viscosity-average molecular weight fractions of three fractions were determined. The intrinsic viscosity were 28.55535, 9.71043 and 4.098695 respectively. The viscosity-average molecular weight were 1.35×105, 2.90×104 and 2.90×104 respectively. The inhibition test of Mycoplasma pneumoniae showed that there was no anti-mycoplasma pneumonia activity in P. grandiflorum polysaccharide. While the anti-oxidation experiments in vitro indicated that PGP-B, PGP-C and PGP-D all exhibited some radical scavenging capacity and total reducing capacity, but less effective than ascorbic acid. PGP-D showed the best ability among the three.PGP-D-a and PGP-D-b were obtained from PGP-D after the purification by DEAE-52 and Sephadex G-100 column chromatography. The infrared spectroscopy showed that these two components were both polysaccharide compounds according to their polysaccharide-specific functional groups. The analysis of monosaccharide composition showed that PGP-D-a was mainly composed of L-rhamnose, D-arabinose, D-xylose, D-mannose, D-glucose and D-galactose. The molar ratio was 0.30:1.00:0.33:0.94:1.77:0.67 with glucose occupying the highest proportion. NMR spectroscopy shows that there were three possible configurations in PGP-Da-1 might, namely, Glc(1�'3)Ara, Glc(1�'4)Glc and β-Glc(1�'4)-β-Glc(1�'4)-α-Glc. And there were no methyl group, sugar acid and glycoprotein.