Extractiona And Purification Of Luteolin From Peanut Shell And Its Antimicrobial Activity

Luteolin is a flavone compound with many bioactivities and high percent in the peanut shell. In this paper, luteolin was extracted from peanut shell with ethanol, the extraction process was optimized; then products were separated and purified with many methods; and the antimicrobial activities of EP-1 and EP-2 were studied. The main results were as follows:1. Under the same conditions, the order of the luteolin's yield was reflux extraction>MAE >ultrasonic extraction: the purity of product from the reflux extraction was 9.85%, while MAE was 15.18%, so the optimum process was determined: microwave power 900W, ethanol concentration 80%, extaction time 70s, ratio of solid to liquid 1:20.2. Peak area method of HPLC was used to determine the purity and components of different products. The results showed that acetic ester extraction enriched the water soluble components, and water deposition could notablely reduce their percents in the products; absolute ethanol dissolution of the dry extract enriched luteolin and another fat-soluble substance; products with high purity could be gotten by TLC.3. The products gotten from loaded-eluted with 30% ethanol on macroporous resin AB-8 had the higher purity and the same with 70% ethanol; loading sample with absolute ethanol showed the largest processing capacity and the target compound was mainly in the part eluted by 70% ethanol; the optimum process of purification using macroporous resin AB-8 was loading sample with absolute ethanol, then eluted with grads and the part eluted by 70% ethanol were fractionally collected.4. EP-1 showed inhibiting or killing effect on the test strains in different degree, and a wide antimicrobial spectrum. In the experiment, the antimicrobial effect was better on the bacterial than on the epiphyte. There was a positive correlation between antimicrobial activity of EP-1 and luteolin concentration and action time. With the same action time, the higher of luteolin concentration, the higher its antimicrobial activity was; with the same concentration of luteolin, the longer of action period, the higher of inhibiting rate on the test strains.5. With the same concentration, EP-2 showed higher antimicrobial activity than EP-1, sorbic acid and sodium nitrite, and had the antimicrobial characteristics of phenols. Synergism effect was found between EP-2 and sodium nitrite on inhibiting the growth of S.ceverce, but not on Staphylococcus aureus26003 and Bacillus subtilis63501. There is no significant synergism effect between EP-2 and sorbic acid on the tested strains. Culture temperature and pH influenced the antimicrobial activities of EP-2 on the test strains.6. The shape of bacterial treated by drug was characterized by microscope, it showed that the structure and function of outer membrane and cell walls were destroyed, and many cell fragments appeared, transportation of nutrition into the cell was prevented, then cell plasmolysis appeared, causing cellular content leakage that led to the antimicrobial effect.