Physical and Chemical Properties of Pectin-proanthocyanidin Complex and Its Antibacterial Activity in Vitro

Objective:Improving the stability and antibacterial activity of procyanidins. Methods:The mango was used as raw material,pectin was extracted by acid method(citric acid at pH2.5).The molecular weight distribution of pectin was determined by gel permeation chromatography. The composition of neutral sugars was analyzed by gas chromatography-mass spectrometry. The characteristic groups were determined by infrared spectroscopy. The esterification degree and the contents of galacturonic acid were determined by titration. The complex was composed of pectin and procyanidins by physical means. The thermal stability,rheological properties,grain size,aeta potential,micromorphology and other physical and chemical properties of pectin and its complex were compared by differential scanning calorimetry(DSC),isothermal titration calorimetry(ITC),rheological properties analysis,nanometer particle size potential analyzer,scanning electron microscope(SEM). On this basis,the inhibition rate of procyanidin and procyanidin-pectin complex on 4 strains of S. aureus was further analyzed. Results:The extracted mango pectin contained two integral points(Mw 2.6724×10⁴ and 2.2525×10⁵,respectively). The molality ratio of rhamnose:fucose:arabinose:xylose:mannose:galactose was 1.226:0.087:1:0.025:006:0.091. The esterification degree was 91.09%±2.23%. The contents of galacturonic acid was 82.32%±0.51%. The glass transition temperature of the composite decreased. The apparent viscosity of the complex was lower than that of pectin at the same mass concentration. The grain size of complex solution decreased significantly and the absolute value of aeta potential increased. Through SEM observation,the surface was smooth and the edge was threadlike. The interaction between pectin and procyanidins was mainly hydrogen bond driven spontaneous exothermic reaction. The inhibition rate of pectin-procyanidin complex on four strains of Staphylococcus aureus was significantly higher than that of procyanidin,and the inhibition effect on S. aureus ATCC27217 was the best with IC₅₀ of 0.006 mg/mL. Conclusion:The mango pectin was an acidic heteropolysaccharide with high esterification degree. When compounded with procyanidins,the thermal stability of procyanidins was significantly improved,the absolute value of zeta potential significantly increased,and the solution grain size greatly reduced and more uniform. The interaction between the two was mainly exothermic reaction driven by hydrogen bonds. The inhibition effect of compound on 4 strains of S. aureus was significantly higher than that of procyanidins.