Feipeng Jiao

Enantioselective extraction of mandelic acid enantiomers by aqueous two-phase systems of polyethylene glycol and ammonium sulfate containing β-cyclodextrin as chiral selector

A new chiral separation technology, aqueous two-phase extraction, was proposed for the separation of racemic mandelic acid. The distribution behavior of mandelic acid enantiomers was investigated in aqueous two-phase systems composed of polyethylene glycol and ammonium sulfate containing β-cyclodextrin as chiral selector. The influences of the pH, the mass fraction of polyethylene glycol and ammonium sulfate, the polymerization degree of polyethylene glycol, the initial concentration of β-cyclodextrin, mandelic acid enantiomers and extractive temperature on the distribution behavior were studied respectively. The results show that β-cyclodextrin is inclined to recognize L-enantiomer; under the optimized conditions, the separation factor reaches 2.46 and the enantiomeric excess is 42.13% in the top phase and 40.43% in the bottom phase, respectively. Aqueous two phase chiral-extraction with strong chiral separation ability, plays great role in preparative separation of racemic compounds and is important for the development of aqueous two phase extraction technique.

Evaluation of Ferulic Acid-Biomembrane Interaction by Liposome Electrokinetic Chromatography

Abstract A facile method for evaluating acidic drug-biomembrane interaction was established by liposome electrokinetic chromatography (LEKC). LEKC is a capillary electrophoresis technique, where liposome is incorporated into a buffer solution and acts as a pseudostationary phase using the structural similarity of liposome and biomembrane. Liposome–water partition coefficient ( K lw ) of ferulic acid was determined within a few minutes. The effect of cholesterol content, buffer pH, and buffer composition on K lw was investigated, respectively. An increase in cholesterol content (0–30%) and pH values (4.00–12.00) resulted in a lower K lw . In different buffer systems, the greater the ionic strength, the larger K lw was. The difference of K lw revealed ferulic acid–biomembrane interaction.

Enantioselective transport of R-clenbuterol through a bulk liquid membrane containing O,O'-dibenzoyl-(2S, 3S)-tartaric

A method of bulk liquid membrane (BLM) using O, O-dibenzoyl-(2S, 3S)-tartaric acid was developed for the enantioselective transport of racemic clenbuterol. The influence of buffer pH, concentration ratio of chiral carrier to clenbuterol were studied. It was an appropriate choice of such as pH 7 in aqueous solution and concentration ratio of 1:4. The model of kinetic transport was established by means of a kinetic model involving two consecutive irreversible first order reactions. The pseudo-first order apparent rate constants were determined. It is helpful for optimizing the transport of BLM systems and realizing the large-scale production of pure enantiomer.

Enantioseparation of Racemic Mixtures Based on Solvent Sublation

A method of solvent sublation was developed for the enantioseparation of racemic ofloxacin (rac Oflx) and racemic tryptophan (rac Trp). In this method, dibenzoyl-L-tartaric acid (L-DBTA) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) and sodium lauryl sulfate (SDS) were used as chiral coextractants and foamer, respectively. Several important parameters influencing the separation performances, such as pH in aqueous phase, concentrations of rac mixtures, L-DBTA, D2EHPA, and SDS, were investigated. Under the optimal operation conditions, the enantiomeric excess and enantioselectivity were 60.08% and 5.58 for Oflx and 65.09% and 6.31 for Trp, respectively. The yields of D-enantiomer and L-enantiomer were 34.23% and 8.54% for Oflx and 18.59% and 3.93% for Trp, respectively. The results suggest that the enantioselectivities have been enhanced compared with the traditional chiral extraction. This technique is an efficient chiral separation method, with many advantages such as low expenditures of organic solvent, low consumption of chiral extractant, and easy realization of multistage operation.

Enantiomeric Separation of Racemic Clenbuterol by Capillary Zone Electrophoresis

A method for capillary electrophoretic enantiomeric separation of a racemic clenbuterol has been established with hydroxypropyl-β-cyclodextrin as the chiral selector. General equations and data analysis are presented to relate mobility to the equilibrium constants in simple binding equilibria and used to determine binding constants and thermodynamic parameters for host-guest complexation of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin as a selector. The effects of β-cyclodextrin type and concentration, buffer type, concentration and pH, as well as separation voltage and capillary temperature were investigated in detail. A maximal resolution of 6.78 was obtained. The binding constants of the host-guest complex of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin, KR-CD and KS-CD are 22.50 and 43.09 l mol-1, respectively.