Study On Extraction, Purification And Inhibitory Effect Of Gallic Acid From Galla Chinensis

Gallic acid is major antibacterial component of Galla chinensis. Its extraction, purification, stability and bacteriostatic effect were studied in this paper. The purpose was find a efficient and security which can be used as antibiotics to prevent animal diseases substitute, used in animal feed additives, it can exempte the animal and human health problem which is caused by antibiotics in animal feed additives of abuse.This study used ethanol reflux, heat reflux, acid hydrolysis three different methods to extract gallic acid from Galla chinensis, Through the single factor experiment and the orthogonal experimental design, the optimum extraction conditions of three methods were showed. Among them, the optimum extraction conditions of gallic acid from Galla chinensis by ethanol reflux extraction were obtained as follows was: the extraction solvent was 60% ethanol (v/v), extraction temperature was 76℃, pH 2, extraction time was 90 min, the solid- solvent ratio was 1:10, extraction number was two; the optimum extraction conditions of gallic acid from Galla chinensis by heat reflux extraction were obtained as follows was: electric heating temperature was about 400℃, hydrochloric acid concentration was 0.36 mol/mL, extraction time was 7 h, the solid- solvent ratio was 1:100; the optimum extraction conditions of gallic acid from Galla chinensis by acid hydrolysis extraction were obtained as follows was: heating temperature of boiling water was 100℃, the solid- solvent ratio was 1:80, the extraction time was 3 h, hydrochloric acid concentration was 4 mol/mL. Under the optimum condition, the extracting ratio of the three methods were 8.35%, 50.9%, 56.3%, respectively. So, acid hydrolysis was the best method to extract gallic acid from Galla chinensis.Compare the gallic acid from Galla chinensis purification methods of the resin, the extracting and the resin - extracting obtained the best purification method was resin - extracting method. First, the select resin was D301, the sample flow rate was 1 mL/min, elution rate was 1 mL/min, elution solvent was 5% HCl -70% ethanol, later used ethyl acetate to extract the purified product, extraction temperature was about 20℃, extraction number was 3, the extract volume ratio was 1:1, each extraction time was 10 min, the purity of the sample was 90.0% finally.Through this experiment, the The obtained purified determined by IR, HPLC, UV, the result showed that its structure was gallic acid.The stability of gallic acid was studied. The results showed that light, heat, pH and preservatives has obviously effect to the purified gallic acid, and pH have the bigest effect. The purified gallic acid was stable under acidic conditions, it decreased stability with pH values increasing, alkaline conditions was extreme instability.Against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Salmonella enteritidis these four strains, 0.09 g/mL of gallic acid from Galla chinensis purified's average diameter of inhibition zone were 4.98,4.25,3.28,3.80 cm, the minimum inhibitory concentration were 0.90,9.00,9.00,9.00 mg/mL, the bacteriostatic effect was obviously higher than Galla chinensis crude extracts. 0.09 g/mL purified gallic acid bacteriostatic effect was obviously lower than 0.1 g/mL penicillin, slightly lower than 0.008 g/mL gentamicin, but the difference was not obvious, but was obviously higher than 0.1 g/mL acetylspiramycin.