| Bitter melon ( Momordica charantia ), a kind of typical traditional medicine herb ,can be used as food and medicine. In this paper, extract of Bitter melon was tested for its antimicrobial activities, including investigation of its antimicrobial spectrum, MIC value; Varieties with strongest activities were selected after comparing the differences of antimicrobial activities of different bitter melon varieties in large quantities by monitoring their antimicrobial activities. Active substances were extracted from the selected materials. The processing conditions of leaching active substances from bitter melon were optimized with response surface analysis (RSA) method; The sensitivity to universal factors of the extract was studied. At the same time, the isolation and purification of the antimicrobial components of bitter melon were also studied .The main results were as follows:1. According to the experiments, we found that the extract of bitter melon had strong inhibition to most bacteria , especially to Staphy lococcus aureus and Escherichia coll., whose MIC value to bacterial was 37.5mg/Ml, MIC value to Staphy lococcus aureus and Escherichia coli. was 18.75mg/mL. So Staphy lococcus aureus and Escherichia coli. were selected as sensitive bacteria to the study .2. Antibacterial activities was compared by diffusion method among twenty five varieties of the selected bitter melon. The result indicated that significant differences was found in antibacterial activities (P<0.01) and that the order of antibacterial activities was oil melon , da ding and white melon . The same variety bitter melon with different grow periods had different antibacterial activities respectively (P0.01), in which bitter melon with commodity autumn had the strongest antibacterial activities. When bitter melon's grow date exceeded commodity autumn, their antibacterial activities evidently decreased .The twenty-five varieties of bitter melon could be clustered into four clusters. The order of antibacterial activities of the clusters was the first cluster, the second cluster, the fourth cluster and the third cluster.3. Bitter melon with different pretreatment showed different antibacterial activities. Dried powder had the best antibacterial activities. The antibacterial activities of extract of bitter melon increased with the adding polarity of solvent, in which 70% ethanol was the best solvent for extracting. The optimum extraction conditions of leaching active substances determined by response surface analysis method were as follows: the concentration of ethanol was 65%; temperature for extracting was 60°C with 4h the ratio of material and solvent was l:40.Under this condition, the one time extraction rate was 38.4% and diameter of antibacterial of the extract was up to 12.39mm. 4. The stability to temperature, acid, alkali, ultraviolet and abiosalt of the extract of bitter melon were also studied. The result showed the extract was very stable to temperature and ultraviolet. Antibacterial activities were better when pH< 7 and the concentration of abiosalt was less than 0.5mol/L. Flavone, alkaloid, hydroxybenzene and organic acid were found in extract of bitter melon, in which anthracene was not found. Extract of bitter melon had strong total antioxidant capacity (TAC), furthermore significant correlations existed between TAC and antibacterial activities.5. All extracts obtained in different fractions by using different polarities of solvents such as petroleum ether, chloroform, ethyl acetate, normal butyl alcohol and water were compared through the testing of their antibacterial activities. The results showed the antibacterial activities of ethyl acetate were strongest and normal butyl alcohol took second place. The biological development technique was used to provide a qualitative analysis method for tracking antimicrobial components in the extracts of ethyl acetate and normal butyl alcohol in which six different antibacterial points appeared after 2 hours diffusion and had five antibacterial components a... |
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