A Study Of Chiral Differentiation Of Enantiomers Using Mass Spectrometry With Metal Ions And ?-CD As Ligands And Its Mechanism

Due to different three-dimensional structures and various binding forms with biomolecules,chiral drug enantiomers have significant differences in the absorption,distribution,metabolism and excretion process,leading to different and even opposite pharmacologic and toxic effect in human.Therefore,the great emphasis should be put on the recognition and isolation of chiral drugs for the drug safety,effectiveness and quality control.However,the chemical and physical properties of chiral drug enantiomers are basically the same,making the recognition and isolation of chiral drug enantiomers become hot and difficult issues in drug analysis.Chromatography is the main technique to differentiate drug enantiomers while it still owns some limitations.Therefore,it is necessary to develop a new method which is more convenient and faster for enantiomeric differentiation.Mass spectrometry(MS)is a powerful analytical technique equipped with remarkable features like sensitivity and speed and has already been applied to separate drug enantiomers hyphenated with chromatography.MS used to be considered as a "chiral-blind" technique because the same mass shows identical mass spectra of the enantiomers.With the development of ionization techniques and deeper understanding on the mechanism of the chiral discrimination,MS has begun to emerge in the field of chiral discrimination in recent years.However,using MS for the enantiomeric differentiation remains to be a big challenge,especially for drugs containing multiple chiral centers,which are rarely reported.Under such circumstance,we studied a novel chiral analytical method using MS called collision-induced dissociation of diastereomeric complex method with metal ions and ?-cyclodextrin(?-CD)as ligands and its recognition mechanism using computer simulation methods.The Study of Recognition of Ezetimibe Enantiomers by MS Using Cu2+ and ?-CD as Ligand and Its MechanismWe investigated the chiral recognition of two Ezetimibe enantiomers(SRS-Ezetimibe,RSR-Ezetimibe)by MS using ?-CD and Cu2+ as ligands and its mechanism using DFT and PM6 methods.In the experiment,25?g/ml ?-CD and 12.5?g/ml Cu2+ were mixed with 25?g/ml Ezetimibe to form a ternary complex which was detected as[Cu(Ezetimibe)2(?-CD)-H]2+ in ion trap MS and Q-TOF MS.After collided in the MS/MS,the[Cu(Ezetimibe)2(?-CD)-H]2+produced several fragments among which the [Ezetimibe-H2O+H]+(m/z=392.15)shows a distinct difference between SRS-Ezetimibe and RSR-Ezetimibe.The recognition of SRS-Ezetimibe and RSR-Ezetimibe was based on the collision-induced dissociation of diastereomeric complex method.In addition,computer simulation results clearly showed the potential binding pattern of ternary complexes in gas phase and revealed the energy difference between them,which can provide a new approach for enantiomeric differentiation.The Study of Recognition of Ezetimibe Enantiomers by MS Using Different Metal Ions and ?-CD as Ligand and Their MechanismsThe effects of Mg2+,Zn2+,Pb2+,Hg2+ and Co2+ combined with ?-CD as ligands on differentiating SRS-Ezetimibe and RSR-Ezetimibe were studied.The computer modeling method was utilized to simulate the data from MS.All of the procedures of MS experiment were the same as those described before.It turned out that different metal ions produced different fragments from the ternary complexes which can be used to recognize SRS-Ezetimibe and RSR-Ezetimibe.Besides,the efficiency of recognition are also different.Furthermore,the computer stimulation results showed potential binding patterns and energy differences of ternary complexes with different metal ions.After analyzing the characteristics of metal ions,we finally made a conclusion that the loss of electron capability and the size of the radius are important factors that affect the discrimination function of metal ions as ligands.The Study of Recognition of Other Drug Enantiomers by MS Using Cu2+ and ?-CD as Ligand and Their MechanismsTo deeply understand the role of the drug enantiomers in the ternary complex and the application scope of our method,we studied the recognition of Captopril and Ibuprofen enantiomers by MS using Cu2+ and P-CD as ligand and their potential mechanisms.Unfortunately,Captopril,?-CD and metal ions cannot form stable ternary complex because the sulfhydryl group of Captopril is oxidated easily in the presence of metal ions.Ibuprofen enantiomers cannot be recognized by P-CD and metal ion complex method either,but can be recognized by D-glucose and metal ion complex.Therefore,there are some limitations for ?-CD and metal ions complex method for recognition of enantiomers.