The Extraction Preparation Of Gallic Acid From Galla Chinensis Tannin And Its Antimicrobial Activities And Related Mechanisms

Gal la Chinensis is a cystic gall produced by some aphis that belong to Pemphigidae and live on the Rhus leaves of the family Anacardiaceae, which is also called the worm bin and clam. Galla Chinensis is a traditional herb of China. Its main chemical compositions include gallotannins, gallic acid (GC), fatty oil, etc. Gallotannins has the rate of80%in the Galla Chinensis. Gallic acid, which is one of the main compositions, has the rate of2%-4%. It’s a kind of Natural polyphenol compounds. Gallotannins of Chineses Galla Chinensis is a kind of hydrolysable tannin. Gallotannins is used to be hydrolysed to produce gallic acid in industry.The researches on the gallic acid from Galla Chinensis (GAGC) are including extraction, purification, antimicrobial activities, antioxidant, antineoplastic activities, antimutation and so on at home and abroad. In respects of extraction, researches have focused on the crude materials or the extract liquid, seldom on the gallotannins. And the antimicrobial activities of GAGC are seldom from the perspective of the food safety.This paper is on the basis of existing research in this lab. First, the experiment employed orthogonal array design to optimize the acidolysis extraction condition of GAGC. The effects of extractive temperature, volume fraction of solvent, concentration of hydrochloric acid and extractive time on the yield of GAGC were investigated. GAGC was purified and its structure was identified. Next, the minimal inhibitory concentration against the six common food spoilage and foodborne pathogens was measured through the liquid doubling dilution method, the antimicrobial properties were screened by oxford cup, and the results were compared with tea polyphenols and gentamicin sulphate. The Microplate Reader was used to detect the growth curves. The effects of pH and temperature on the antimicrobial activities of GAGC were observed and researched. Finally, the leak of the internal substance, including nucleic acid, K+, Mg2+, and the protein of the tested bacteria were investigated through spectrophotometer. The modification on strain morphology of the tested bacteria was investigated by scanning electron microscope.The main achievements are showed as follows:(1)The experiment employed orthogonal array design to optimize the acidolysis extraction condition of GAGC. The optimal extraction condition of GAGC are showed as follows:extractive temperature is100℃, volume fraction of solvent is1:100, concentration of hydrochloric acid is5mol/mL and extractive time is5h. At this condition, the yield of GAGC is18.72%. The purity of GAGC after purification is80.12%. And the sample was determined by HPLC, UV. The results showed that the sample’s structure was GC.(2) The minimal inhibitory concentrations of Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, Bacillus subtillis, Bacillus cereus and Bacillus megaterium were0.125,0.25,2,4,4and4mg/mL. The antibacterial circles were (20.67±0.28) mm,(17.17±0.64) mm,(24.03±0.17) mm,(14.43±0.10) mm,(14.77±0.04) mm,(15.07±0.03) mm。Growth curves were changed and logarithmic phases were restrained. GAGC had antimicrobial activities below60℃. When temperature was80℃, GAGC had antimicrobial activities on Escherichia coli and Listeria monocytogenes, and antimicrobial activities on the other four tested bacteria were decreased. When temperature was100℃, GAGC had no antimicrobial activitiy on all tested bacteria. When pH was between3and5, GAGC had antimicrobial activities. When pH was6, GAGC had antimicrobial activities on Escherichia coli and Listeria monocytogenes, and had no antimicrobial activitiy on the other four tested bacteria. When pH was7, GAGC had antimicrobial activities on Listeria monocytogenes, and had no antimicrobial activitiy on the other four tested bacteria. When pH was8, GAGC had no antimicrobial activitiy on all tested bacteria.(3) The protein of the tested bacteria was reduced, and the nucleic acid, K+and Mg2+were increased. The shape of the tested bacteria were changed: the Escherichia coli depressed and showed obviously rough on the surface of the bacteria; the Listeria monocytogenes depressed on center, most of the cell walls were damaged, obvious contents were leaked out and bacteria stayed together.GAGC may damage the cell membrane, leading to the leak of the internal substance and the inhibition of the growths which result in the death of the tested bacteria.