Study On Preparation And Biological Activity Of The Lactulose Derivatives

Lactulose is 4-O-?-D-galactopyranosyl-D-fructose,a synthetic disaccharide composed of two sugar molecules fructose and galactose bounded together with ?-1,4-glycosidic bound.Lactulose is more likely to dissolve in water and its sweet is half than that of saccharose,Lactulose is considered as a prebiotic because it promotes the intestinal proliferation which is added to various milk products.Moreover,lactulose is used in pharmaceuticals as a gentle laxative and to treat hyperammonemia.Due to lack of adequate researches in different linkages of Lactulose,In this research work we focus on comparing different linkages of Lactulose and their bioactivities.This paper was aimed at the total synthesis of two Lactulose-derived oligosaccharides:one is 3-O-?-D-galactopyranosyl-D-fructose,D-fructose and ?-D-galactose bounded together with ?-1,3-glycosidic bound,the other is 1-O-?-D-galactopyranosyl-D-fructose,D-fructose and ?-D-galactose bounded together with ?-1,1-glycosidic bound,which were accomplished in seven steps from D-fructose and ?-D-galactose.At first,?-D-galactose is protected by acetyl and 1-acetyl is reduced hydroxy,1-hydroxy is protected by trichloroacetimidate to obtain the donor of glycosylation.The 1-hydroxy and 2-hydroxy,4-hydroxy and 5-hydroxy of D-fructose is protected by the propyl ketal,as well with 2-hydroxy and 3-hydroxy,4-hydroxy and 5-hydroxy of D-fructose to obtain two acceptor o f-glycosylation.Then,these donor and acceptor of glycosylation through condensation to get condensation products,which yield is 75%and 78%.Finally,the condensation products wipe off the protection of acetyl and propyl ketal to get the advanced glycation end products.This synthetic route provided a practical and effective strategy for galactooligosaccharides,starting from commercially available monosaccharides.The final products after being detected by thin-layer chromatography(TLC)and purified through silica gel column.The purified fractions were identified and characterized with MS and 1H-NMR and 13C-NMR.Then their prebiotic properties have been evaluated in the search for potential agents of regulating and improvingc the intestinal flora of human.3-O-?-D-galactopyranosyl-D-fructose and 1-O-?-D-galactopyranosyl-D-fructose displayed higher proliferation than 4-O-?-D-galactopyranosyl-D-fructose.Among them,3-O-?-D-galactopyranosyl-D-fructose displayed the most potent activity of proliferation of Lactobacillus acidophilus.