Extraction And Separation Of Bacteriostatic Compositions From Senna And Study On Its Antimicrobial Activity

Senna is a kind of Chinese herbal medicine used as antibacterial, purgative and hemostatic. In this paper, the bacteriostatic activity of senna was studied using tomato late blight bacteria as tested strains, and extraction and separation of these compositions were studied too. The results were as follows:1、the optimal extraction condition of antimicrobial substance from senna were obtained as follows:ethanol concentration50%, extraction temperature40℃, ratio of solid to liquid1:14, extraction time3.5h, repeated for twice. The inhibition zone for tomato late blight reached22.5mm.2、The extraction of senna has great stability to temperature and ultraviolet light. The antibacterial activities were increased by adding metal ion or pH<7. The MIC of the senna extractions was12.5mg/mL for tomato late blight. This antibacterial effect was equal to1400times diluent of tomato red external present1600times diluents of tomato early and late phytophthora and1200times diluents of carbendazim.3、The chemical constituents of the senna have been tested systematically by tube-test. It was found that the senna contains flavonoids, alkaloids, tannin, dexidize sugar, organic acid, volatile oil and so on. It may contain phenylpropanoids, steroids, cardiac glycoside, phenols and no saponins.4、Using four solvents being of different polarities, five extraction part-were obtained, which were petrolem ether part, chloroform part, ethyl acetate part, butyl alcohol part and residue part. The antimicrobial activities of five parts were tested respectively and found that ethyl acetate part showed stronger bacteriostatic activity.5、The further purification was carried on using Thin Layer Chromatogram and Silica Gel Column, and analysed by nuclear magnetic resonance spectrometry. The result showed that one of the active constituent was emodin.6、The cell membrane permeability of tomato late blight bacteria was evaluated by the permeability conductance method. The result indicated that the cell membrane permeability of the bacteria was destroyed by active component of senna. Meawhile the senna caused electrolyte large extravasation, which finally leading to cells death.