Design, Synthesis And Brain Targeting Research Of Prodrug Of Ginkgolide B

As an important active component of extraction of Ginkgo biloba leaves, Ginkgolide B (GB)has natural and effective antagonism of platelet activating factor (PAF) receptor, as well assignificant anti-ischemic brain injury. However, the content of GB into the brain is limited,bioavailability is not high, and there is still room for the improvement of brain targeting of GB.Prodrug strategy is commonly used for improving the brain targeting of drugs, with the advantagesof high safety and easy achievement. Therefore, by using GB as parent nucleus, design of prodrugs,virtual screening, synthesis and characterization, and brain targeting evaluation were systematicallycarried out in this dissertation. The results are listed as follows:1. The results of virtual screen hinted that10-O-nicotinate GB (GBN) was a double-targetedprodrug of GB with higher drug-likeness and better brain targeting.Based on80compounds with known brain targeting as training set, five molecular descriptors(molecular volume (Mv), partition coefficient (logP), polar surface area (PSA), number of rotatablebonds (NRB) and high affinity P-glycoprotein substrate probability (HAPSP)) as variables, ageneralized prediction model of blood brain barrier permeability was constructed by using multiplelinear regression method. The investigative results of the importance of five molecular descriptorsshowed that the most important one was HAPSP, followed by logP, NRB, PSA and Mv.Six kinds of prodrugs of GB (10-O-acetate GB,10-O-benzoate GB,10-O-nicotinate GB,10-O-5-methylpyrazine-2carboxylic ester GB,10-O-cinnamate GB and10-O-ferulic acid ester GB)were virtually screened by combining generalized prediction model of blood brain barrierpermeability and evaluation software of drug score from OSIRIS Property Explorer. The resultsindicated that the drug score of10-O-nicotinate GB was highest, and its predictive blood brainbarrier permeability was better than that of parent drug GB. In addition, nicotinic acid also hassome pharmacological activity, and after combining with GB to form two-targeted prodrug, it couldplay synergistic therapeutic effect in vivo.2. The targeted prodrug GBN was synthesized and its structure was confirmed.By using GB and nicotinic acid as material, acetonitrile as solvent, EDC and DMAP asdehydrant and catalyst, respectively, a new prodrug of GB-GBN was synthesized. The productwas confirmed by mass spectrum, infrared spectrum and nuclear magnetic resonance analysis.3. The brain targeting of GBN was better than that of parent drug GB, and the calculateddrug-targeting index (DTI) value of GBN was7.50.The liquid chromatography tandem mass spectrometry (LC-MS/MS) method was establishedand validated for simultaneous determination of GBN and GB in rat brain homogenate. Then the method was applied to investigate the pharmacokinetics of different drugs in rat brain afterintravenous injection of GBN or GB. The results showed that, compared with injection of parentdrug GB, the elimination rate of GB decomposed from GBN was slower, and the concentration washigher in brain. After calculation by3P97software, the pharmacokinetics of GBN, GB decomposedfrom GBN and parent drug GB was consistent with two-compartment model in brain homogenate;the elimination half-life (t1/2β), mean residence time (MRT) and area under the curve (AUC) valueof GB decomposed from GBN in brain were5.03,5.76and2.45times that of parent drug GB; butthe clearance rate of parent drug GB in brain was1.96times that of GB decomposed from GBN,indicating that GB decomposed from GBN had a sustained-release effect in brain. The calculatedDTI value of GBN was7.50, which suggested that compared with parent drug GB, the braintargeting of GBN was improved.4. In plasma, the elimination half-life of GB decomposed from GBN (121.73min) was longerthan that of parent drug GB (77.61min), demonstrating that GBN could play a long-lasting effect.The LC-MS/MS method was established and validated for simultaneous determination ofGBN and GB in rat plasma. Then the method was applied to investigate the generalpharmacokinetic properties of different drugs in rats after intravenous injection of GBN or GB. Theresults showed that, in plasma, the pharmacokinetics of GBN, GB decomposed from GBN andparent drug GB was consistent with two-compartment model; the t1/2β, MRT and apparent volumeof distribution (Vd) of GB decomposed from GBN were1.57,1.39and5.63times that of parentdrug GB. These results suggested that compared with injection of parent drug GB, injection ofGBN could play a long-lasting effect.