Structures Of Fructan And Galactan From Polygonatum Cyrtonema And Their Utilization By Probiotic Bacteria

Polygonatum cyrtonema Hua,as a kind of Traditional Chinese Medicine with the property that one material can be used for both nourishment and therapy(known as homology of medicine and food in China),is widely planted and applied throughout the country.Polysaccharides which may be closely related to the P.cyrtonema’s tonifying effect are the most abundant component among the diverse chemical composition,but there are wide variety and complex chemical structures for the polysaccharides,making it difficult to analyze their structures.In this research,two polysaccharides were isolated from P.cyrtonema and were analyzed structurally.After that,their prebiotic activities were investigated.Extraction and purification of the P.cyrtonema Polysaccharides: The polysaccharides were extracted from the dried and processed rhizomes of P.cyrtonema by hot water extraction,and purified by precipitation with ethanol and quaternary ammonium salt,and anion-exchange chromatography etc.The polysaccharides DP1 and PP1 were obtained,and their yields were 11.40% and 0.89%,respectively.The physicochemical properties and structural elucidation of DP1 and PP1:The physicochemical properties and structures of the two polysaccharides were studied by various chemical and spectral methods.The results of molecular weight determination and monosaccharide composition showed that DP1 was a hetero-polysaccharide with a weight-average molecular mass of 3498 Da and was composed of fructose(Fru)and glucose(Glc)and PP1 was a homo-polysaccharide galactan with 7019 Da;methylation analysis revealed that DP1 mainly consisted of fructose linked by β(2→6)and β(2→1),and the galactan PP1’s glycosidic linkage type was β(1→4);the IR spectroscopy and the NMR data combining with above analysis showed that DP1 should be classified as a neoseries fructan similar to agavin consisted of →1)-β-D-Fruf-(2→ and →6)-β-D-Fruf-(2→ in neoseries form,and PP1 was a galactan possessing a 1,4-linked β-D-galactopyranosyl backbone,with aβ-D-galactopyranosy stub attached to O-6 of every 9th galactosyl residue.The prebiotic activity study of DP1 and PP1: After structure analysis,the prebiotic activities of the two polysaccharides were further explored.The fructan DP1 and the galactan PP1 were added to the basic medium without any direct carbon source,respectively.Four probiotics were inoculated and then cultivated anaerobically.During 48 hours of culture,the p H,OD600 nm and the number of probiotics in each culture medium were measured,and the growth curve of bacteria number and culture time was fitted.The results showed that DP1 and PP1 both promoted proliferation significantly on four strains Bifidobacterium animalis subsp.lactis,B.bifidum,Lactobacillus acidophilus and L.plantarum.Further analysis showed that polysaccharide DP1 and PP1 were selective by different probiotics.In this thesis,a fructan and a galactan with complex structures were isolated and purified,and studied.The prebiotic activities of polysaccharides DP1 and PP1 were preliminarily investigated.The results deepened the understanding of the structure of the fructan and the galactan,highlighted the prebiotics activity of the two polysaccharides,and provided a reference for the efficacy elucidation and further application of the famous tonic medicine Polygonati rhizoma.