Isolation, Identification, And Fermentation Activity Of Oligofructose Monomer From Garlic

Garlic oligofructoses (GOS) has been used as function food. But the function of GOSreported was evaluated by the mixture of GOS, not monomer. In order to assess the biologicalactivity of GOS accurately, it is necessary to separate its monomer. GOS with various molecularweights was prepared from dry garlic by extracting with ethanol, extraction, and adsorbed bypreparation Silica gel column. Then the separation of GOS was analysis by TLC, Flash HILICcolumn, preparation silica gel column, organic solvent, and Bio gel P-2column. The molecularweight of GOS monomer was analysed by HPLC-MS. And structure was studied by NMR.Fermentation properties of GOS with different DP were also be researched through titratableacidity, dilution plate colony counting, and HPLC. The main results were ummarized asfollowing.1. GOS with the content of89.08%(w/w) was obtained.2. The method detection eight sugars simultaneously was established by TLC. Theconditions were:0.4μl (2%, w/w) of GOS,10cm length of silica gel plate, thedeveloping solvent Ⅳ, n-butanol∶ isopropanol∶ water∶a cetic acid=7∶5∶4∶2(v/v/v/v), or the developing solvent Ⅶ, ethyl acetate∶a cetic acid∶i sopropanol∶ water=5∶2∶1∶3(v/v/v/v),four developments at room temperature. Seven sugars withDP=1-7or eight sugars with DP=1-8were separated. The sugar spots were clear andfocus, with high resolution, and an appropriate degree of separation.3. Flash HILIC column could effectively separate monosaccharides and reduce smallmolecule impurities from GOS under the conditions of mobile phase, acetonitrile∶ water=65∶35(v/v),flow rate of1ml/min at room temperature.4. The monomer of GOS with DP3, DP4, and DP5, the mixture of GOS with DP6-9wereobtained through preparation Silica gel column, under the conditions of mobile phase,n-butyl alcohol∶acetic acid∶ water=20∶1∶1(v/v/v), flow rate of2ml/min at roomtemperature.5. The monosaccharide, disaccharide, trisaccharide and other impurities were removed fromGOS, with the solvent of methanol∶ n-butanol=3∶7or4∶6(v/v), under theassistanceof suction filtration at room temperature.6. The GF3, GF4of GOS monomers, with α-D-glucosamine residue, were separated by Biogel P-2column (1.5×100cm), respectively. The conditions were: room temperature(10°C), a flow rate of0.2ml/min. Mobile phase was distilled water, and collected asample every5min. 7. The fermentation rate of GOS increased with decreasing DP value. GOS could not or noteasy be fermented by lactic acid bacteria when DP>9. But the fermentation rate of thesame DP of GOS on different types of lactic acid bacteria was no significant difference(P>0.05).