Screening The Dipeptidyl Peptidase Ⅳ Inhibitors From The Chinese Herb And It's Pharmacodynamics

Dipeptidyl peptidaseⅣ(dipeptidyl peptidaseⅣ, DPP-Ⅳ; EC3.4.14.5/CD26) is an important target for the treatment of diabetes which is one kind of proline oligopeptide of serine aminopeptidase. It has been showed that glucagon-like peptide-1 have significant hypoglycemic effects in vitro and in vivo. However, GLP-1 action has a very shot half life of about 2 min due to its degradation by DPP-Ⅳ, which limited its clinical application. DPP-Ⅳinhibitors have been proved to prevent GLP-1 degradation and thus effectively decrease blood glucose. There are a numbers of compound have been taken part in PhaseⅡ, PhaseⅢclinical trials. Some even have been pushed to the market. The aim of this thesis is to screen the Traditional Chinese Medicine which have the inhibitive activity of DPP-Ⅳ, so as to make the basis for obtain the new structure of the chemical material in future.With Gly-Pro-PNA as a substrate,DPP-Ⅳactivity was assayed by the chromogenic substrate, which was the model for screening DPP-Ⅳinhibitors from Traditional Chinese Medicine in vitro. The concentration of DPP-Ⅳand Gly-Pro-PNA, temperature, pH and reaction time in this method was optimized. The optimal enzymatic reaction system was as follows: DPP-Ⅳ0.5 U/L, Gly-Pro-PNA 0.262μmol/L, 37℃, pH 8.2, reaction for 60 min.A library of natural medicine plants which contained 323 kinds of Traditional Chinese Medicine was developed. Leech, Poria cum Radix Pini and Buddleja officinalis Maxim were searched out according to the model above. The inhibitory activities of these three Traditional Chinese Medicine were all positively related to their concentration. Among them, the DPP-Ⅳinhibitory activity of Buddleja officinalis Maxim was significantly higher than the other two Traditional Chinese Medicines at the same concentration.The hypoglycemic effects of these three Traditional Chinese Medicine extracts were analyzed by the physiological state and fasting glucose level of alloxan diabetic mice. The effect of Leech and Buddleja officinalis Maxim on postprandial blood glucose, serum insulin and GLP-1 levels of alloxan diabetic mice were further investigated. The results showed that Leech and Buddleja officinalis Maxim had hypoglycemic effects in vivo, which was related to the inhibition of DPP-Ⅳ. While Poria cum Radix Pini did not have significant hypoglycemic effects in vivo.