Inhibitory Effects Of Nitric Oxide Sensitive Ursolic Acid Derivatives And Pegylated Uam Liposomes On Hela Cells

Ursolic Acid(UA) with promising remedial value, is the major components of some oriental and traditional medicine herbs wildly distributed all over the word. UA has been shown to suppress tumorigenesis, inhibit tumor promotion, and suppress angiogenesis for kinds of tumor. However, its applications is limited due to its cytotoxicity, low bioavailability, less target specificity in the biological systems. In recent years, in order to reduce the toxicity and enhance the bioavailability rate of UA, various derivatives have been synthesized. The carboxyl group at C-28 position is a key active group to maintain the anticancer potential of UA. According to a number of reports, the amount of nitric oxide in tumor tissue is higher than that in normal tissue. While, UA derivatives that are sensitive to nitric oxide have not been synthesized yet. This thesis is devoted to develop a high nitric oxide sensitive UA derivative which can minimize the damage to normal tissue and improve bioavailability.Through modification, we got UAM, a UA derivative, whose structure was defined by 1H-NMR(H-nuclear magnetic resonance). By tracking and monitoring with TLC(Thin-layer chromatography) and UV-Vis Spectrophotometer, we found that UAM was sensitive to nitric oxide at even low nitric oxide concentration environment. UAM long circulating liposome modified by polyethylene glycol was prepared by ether injection method and Ultrasonic Cell Disruptor. FTIR Spectrometer detection confirmed UAM was modified by polyethylene glycol. According to HPLC(High Performance Liquid Chromatography), Encapsulation effiiency of this UAM liposome was 97.13%, and the drug loading was 3.42%. Measured by Laser particle size analyzer, particle diameter of empty liposome without UAM was 20-40 nm, while the one with UAM was 40-80 nm. MTT was used to detect the inhibitory effect of UA, UA derivative and long circulating liposome on HeLa cells. The result shows in high drug concentration environment, UAM has no cytotoxicity in short time, and as time went on, UAM reached the similar inhibitory effect on HeLa cells as UA did. On the other hand, in low drug concentration environment, UAM demonstrated stronger inhibitory effect than UA. The inhibitory effect was weakening after nitric oxide enzyme inhibitor was added, which indicates that UAM can be dissolved with the effect of intracellular nitric oxide. UAM liposome modified by polyethylene glycol had better water-solubility than UAM, which allows it easily to enter cells and play its role in low drug concentration environment and needs shorter time. In conclusion, this nitric oxide sensitive UA derivative and UAM liposome are effective targeting antitumor drugs which have great potential in antitumor drug releasing field.