| The extraction, purification and inhibition effects of saponins were studied in this paper.The major results are shown as follows:(1) The extraction technique of ultrasonic extration was optimized by response surface method. The results showed that the optimun conditions were that supersonic wave time 22 min,extracting temperature 43℃, supersonic power 403W,and the ratio of bittermelon to solvent 1:51(g/ml),the concentration of alcohol 75%.Under such conditions the extraction rate of total saponins could be up to 4.53% at one-time extraction.(2) Four macroporous resins were screened through the equilibrium adsorption experiments and equilibrium desorption experiments .The D101 resin was determined to purify the total saponins in Alfalfa according to the experiment results.D101 resin adsorptive capacity is larger and the result is 92.86mg/g.The optimum purification conditions confirmed by using dynamic adsorption experiment were as follows:the pH value of absorbing solution was 8-9,the absorbing velocity of flow was 1.0 ml/min,the proportion between the volume of absorbing solution and resins was 8:1,the concentration of ethanol was 80%.(3) Saponins had inhibitory effect on Escherichia coli,Bacillus subtilis,Staphylococcus aureus ,penicilliun citrinum,Rkizopus nigricans and Aspergillus niger.it was very stable to temperature. Within the same action time, the higher extract concentration, the higher its antimicrobial activity was; with the same concentration of extract , the longer of action time, the higher of inhibiting rate on the test strains. It was found that saponins had aggarent inhibiting effect on bacterium and bacillus subtilis in food.
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