Chiral Recognition And Molecular Interaction Of Anticholinergic Muscarine Receptor Drug Phencynonate

The differences of the pharmacological effects for chiral drugs in vivo often are realizedby the chiral recognition, mutual match and interaction between the biomacromolecules andchiral molecular isomer in vivo. The characteristic stereoselectivity of chiral drugs canproduce some changes in pharmacokinetics, pharmacodynamics, toxicology and other aspects.These differences may eventually lead to produce various treatment effect and toxic actions.Phencynonate{N-methyl-9α-(3-azabicyclo[3,3,1]nonanyl)-2’-cyclopentyl-2’-hydroxyl-2’-phenylacetate}(PC) is a novel chiral drug that had markedly anticholinergic muscarinereceptors and developed by the Institute of Pharmacology and Toxicology, Academey ofMilitary Medical Sciences, with independent intellectual property rights. It was reported thatPC had significant effects for preventing the motion sickness, the Meniere’s disease,Parkinson’s disease and epilepsy. Especially, PC prevents motion sickness with higherefficacy and lower central inhibitory as the low side effect. PC has a chiral carbon atomwhich forms a pair of enantiomers. The results showed that the pharmacological activities ofPC isomers had significant differences, and its pharmacokinetics and distributioncharacteristics in target tissue of the brain had also the remarkable stereoselectivitydifferences. Among them, S-enantiomer of PC is as the advantaged enantiomer inpharmacokinetic and pharmacodynamic performance, but up to now, the mechanism of thedifference produced via what is not yet clear. Therefore, the study of chiral recognition andinteraction between PC enantiomers and macromolecules has important academic andpractical value for revealing the difference mechanism of PC enantiomers inpharmacodynamics, pharmacokinetics and toxicology, and will can also provideexperimental data for reasonable development of new single enantiomer drug and optimalguidance to clinical rational drug use.According to the chemical structure and pharmacological profile of PC, the massspectrometry, NMR spectrum, ultraviolet spectrum and the molecular mimicry technologywere used to systematically study the chiral stereoselective recognition, match andinteraction between the isomers of PC and the macromolecules such as β-cyclodextrins(β-CD),2,3,6-tri-methoxyl-β-cyclodextrins (TM-β-CD), ctDNA or M receptor proteins. Theresults provided important information for revealing the molecular basis in pharmacokineticand pharmacodynamic differences of PC isomers.At first, PC-β-CD inclusion compound was prepared, the optimal proportion wascalculated, and the charge mass and inclusion rate were also determined, finally, theformation of PC inclusion was verified. The results showed that the optimal proportion between PC and β-CD was1:2, and its charge mass and inclusion rate were33.30%and80.20%, respectively. By the methods of the ultraviolet absorption, microscope observationand X-ray diffraction, PC inclusion was verified and PC-β-CD inclusion was effective andrelative stable.The combination and chiral recognition between PC and β-CD or TM-β-CD werestudied with the cascade quadripole mass spectrometry. The results indicated that there was aeffective combined action between β-CD and PC, but the chiral recognition ability of β-CDfor the two PC isomers was not significant. There was a markedly stereoselective recognitionand different binding force between TM-β-CD and the PC isomers, which could be due to thespecific space configuration and the different active group of TM-β-CD. TM-β-CD can beused as an effective chiral recognition agent for PC and its derivative isomers.The results in the NMR and2D-NOESY experiments showed that after PC wasembeded in β-CD, the chemical shift of H3and H5protons in the internal hydrophobic cavityof β-CD was transmited to the high field, which verified that the binding action betweenβ-CD and PC racemate existed. Compared with the R-PC, the change of chemical shift at theprotons for S-PC was relatively more evident, indicating that the binding ability betweenS-PC and β-CD may be stronger.The results in the UV experiments showed that the molecular interactions both existedbetween S-PC or R-PC enantiomers and ctDNA. The inset action was given priority in theiraction mode. However, there was no remarkable difference in the interactions between twoenantiomers and ctDNA.The results in the molecular mimicry experiments indicated that the bridge ring sectionof S-PC was bound with the hydrophobic cavity of the M2receptor via the hydrophobicaction; at the same time, the carbonyl oxygen in the molecule formed stronger hydrogenbonds, which further stabilize the whole structure of the complex. From the interactiondifference between both S-PC and R-PC enantiomers and M2receptor and the data of freeenergy calculated, it was qualitatively infered that the ability of S-PC binding to M2receptorwas superior to R-PC isomer. These results was consistent with that S-PC had a strongeraction against the M receptor and a longer half-life in the in vivo pharmacokineticcharacteristics.