A new stereoisomeric monoterpene glycoside and five already-known compounds were isolated from the n-BuOH soluble fraction of Clematis heracleifolia leaves. On the basis of spectral data, the structures of the isolated compounds were identified as protocatechuic acid (1), ferulic acid (2), caffeic acid (3), aesculin (4), (6Z)-9-hydroxylinaloyl glucoside (5), and 9-hydroxylinaloyl glucoside (6) and these were isolated for the first time from this plant. Among these compounds, (6Z)-9-hydroxylinaloyl glucoside (5) is a newly isolated from plant source.
Clematis* ; Esculin ; Plants ; Stereoisomerism*

In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-β-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain β-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of β-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in β-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.
Glycosides ; Mannosides ; Glycosylation ; Stereoisomerism

The chemical constituents of Chinese red ginseng (Panax ginseng) were investigated. The chemical constituents were isolated and purified by silca gel, ODS, and Sephedex LH-20, column chromatography, and preparative HPLC. Their chemical structures were elucidated on the basis of physicochemical properties and spectra data. Fourteen compounds were isolated and identified as: notoginsenoside R2 (1), 20(S) -ginsenoside Rg3 (2), 20(R) -ginsenoside Rg3 (3), 20 (S)-ginsenoside Rg2 (4), 20(R) -ginsenosideRg2 (5), 20 (S)-ginsenoside Rh1 (6), 20(R) -ginsenoside Rh1 (7), ginsenoside Rh4 (8), -Ro (9), -Rb1 (10), -Rg1 (11), Re-(12), Rf (13), maltol (14). Compounds 1, 4, 6, were obtained from red ginseng for the first time. Compounds 2 and 3, 4 and 5-7 were enantiomers respectively, enantiomers 6 and 7 were isolated as monomer for the first time.
Ginsenosides ; analysis ; chemistry ; Panax ; chemistry ; Stereoisomerism

OBJECTIVETo determine enantiomeric impurity in levocetirizine tablets by using capillary electrophoresis.

METHODSThe effects of pH and the concentrations of sulfated-Β-cyclodextrin (S-Β-CD) and buffer salt on chiral resolution were examined with S-Β-CD as chiral selector.

RESULTSA good enantioseparation of cetirizine was achieved with 30 mmol/L NaH2PO4 buffer solution (pH 7.0) containing 20 g/L of S-Β-CD.

CONCLUSIONThe method developed in the study is sensitive and reliable for determination of enantiomeric impurity in levocetirizine tablets.

Many psychotropic drugs are marketed and prescribed as a racemate form in a mixture of the stereoisomers. A chiral center or a center of unsaturation of carbon atoms in the chemical structures creates various stereoisomers of the psychotropic drugs, including antidepressants such as fluoxetine and venlafaxine, etc. The stereochemical significances of enantiomers on the pharmacokinetics and pharmacodynamics of several psychotropic drugs and their relationships with pharmacogenetic polymorphisms were reviewed. The single enantiomer drugs will be increasing more in the market shares replacing the racemic drugs by chiral switching, which is driven by the development of the analytical and preparative resolution techniques and will be of much benefit to the treatment from low dosages, simple dose-response curve, few adverse reactions, and so on.
Antidepressive Agents ; Carbon ; Fluoxetine ; Pharmacokinetics ; Psychotropic Drugs* ; Stereoisomerism ; Venlafaxine Hydrochloride

AIMTo establish a resolution method for alpha-cyclohexyl mandelic acid enantiomers by enantioselective extraction and to observe the effects of all kinds of tartaric esters, pH, the concentration of D-tartaric esters and beta-cyclodextrin on the enantioselectivity.

METHODSResolution of alpha-cyclohexyl mandelic acid enantiomers by enantioselective extraction with tartaric esters and beta-cyclodextrin has been studied.

RESULTSThe distribution behavior of alpha-cyclohexyl mandelic acid enantiomers in the separation system was studied. The effects of all kinds of tartaric esters, pH, the concentration of D-tartaric esters and beta-cyclodextrin on the enantioselectivity has been examined in the two-phase.

CONCLUSIONResults showed that the complex formed by D-iso-butyl-D-tartaric ester with R enantiomer is stabler than that with S enantiomer. With the increase of pH, the partition coefficient and separation factor decreased. The concentration of beta-cyclodextrin and D-tartaric ester had visible effect on the enantioselectivity.

OBJECTIVETo establish a precolumn chiral derivatization method for determination of fexofenadine enantiomers, a chiral substrate of OATP1B1, in cellular model.

METHODSR-(+)-phenylethyl isocyanate was selected as chiral derivatization reagent, which was reacted with fexofenadine to form carbamate derivatives. Enantiomers were identified by LC/MS and separated by RP-HPLC.

RESULTSUnder the experimental conditions, the fexofenadine enantiomers were separated completely. The standard curve was linear over the concentration range of 25-100 ng/ml (R(2)=0.9992, 0.9989). Accuracy was 101.1% and 98.3%, intra-precision was 2.4% and 3.1%, inter-precision was 3.1% and 4.0% for D1 and D2, respectively.

CONCLUSIONThe method established is sensitive and accurate for determination of fexofenadine enantiomers in cells.

OBJECTIVETo develop a capillary electrophoresis system for enantiomeric impurity test of repaglinide.

METHODSAn uncoated fused silica capillary (50 μm×50 cm, with an effective length of 41 cm) was used. The running buffer was composed of 30 mmol/L NaH2PO4 and 5 mg/ml carboxymethyl-β-cyclodextrin(pH 3.5).

RESULTSLinear range was 2.00-80.00 μg/ml (correlation coefficient was 0.9993). The average recovery rate was 92.5% to 105.0%.

CONCLUSIONThe method is simple, accurate and sensitive and it can be used for determination of enantiomeric impurities in repaglinide tablet.

A chiral high-performance liquid chromatography method was developed for the simultaneous determination of ibuprofen enantiomers in dog plasma. It was used to study the pharmacokinetics in the Beagle dog after intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen. Ketoprofen was chosen as the internal standard. After a simple precipitation using methanol as the precipitating solvent, both analytes and IS were separated on a Kromasil 100-5CHI-TBB chiral column (250 mm x4.6 mm, 5 μm) with isocratic elution using acetonitrile - 20 mmol x L(-1) phosphate buffer (pH 3.0, containing 5% methanol) (6 : 4) as the mobile phase. The detection wavelength was 220 nm. Liner calibration curves for both of the ibuprofen enantiomers were over the concentration range from 0.5 to 50 μg x mL(-1) with a lower limit of quantification of 0.5 μg x mL(-1), the accuracies were all in standard ranges. The intra- and inter- assay precisions were all below 7%. The recovery rate was 93.1% to 100.4%. The experiments proved that the method was simple, rapid and sensitive. It can be used in the quantitative determination of ibuprofen enantiomers in dog plasma. The method was used to determine the concentration of ibuprofen enantiomers in Beagle dog plasma after a single intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen (9 mg x kg(-1)) and the pharmacokinetics parameters were calculated based on the concentration-time curves. The C(max) of S-ibuprofen in Beagle dog plasma after a single intravenous administration of racemic-ibuprofen, S-ibuprofen and R-ibuprofen were 30.8 ± 4.7, 46.1 ± 5.9 and 20.0 ± 2.6 μg x mL(-1), respectively. In terms of the exposure of active ingredient, it revealed a significant difference between the administration of S-ibuprofen and the other two groups. The systematical R- to S- chiral inversion was discussed. Comparing the pharmacokinetic parameters at different doses, chiral inversion were 70.1% ± 36.6% and 76.4% ± 36.2%, respectively, after intravenous administration of racemic- and R-ibuprofen. This study provides a theoretical basis for the safety of ibuprofen formula of injection drug.
Animals ; Chromatography, High Pressure Liquid ; Dogs ; Ibuprofen ; blood ; pharmacokinetics ; Stereoisomerism

BACKGROUND: Levobupivacaine is known to be less cardiotoxic than racemic bupivacaine but some authors have reported there were no differences in cardiotoxic profiles between two agents. We will investigate the full course to cardiovascular collapse induced by bupivacaine stereoisomers in anesthetized dogs and would find out the differences if any, and explain the causative factors. METHODS: Twenty dogs were assigned to two groups, racemic bupivacaine group (BUP) and levobupivacaine group (LBUP), equally (n=10, each). Under general anesthesia each drug was infused continuously (0.5 mg/kg/min) until cardiovascuar collapse (CVC, MAP=40 mmHg) occurred. During the experiment, hemodynamic data, CO, SVR, PVR, ECG parameters and drug concen tration were gathered and analyzed. RESULTS: Two groups were not different in terms of dose for CVC, plasma drug concentration and time for CVC. MAP maintained initial values during the early period and declined during the late period without any between-group difference. Otherwise CO decreased continuously and significantly higher in LBUP than in BUP throughout. Calculated SVR showed the same feature as CO in opposite direction and was higher in BUP. Correlation test revealed high correlation between CONC and SVR or PVR and between CO and cSvO2. CONCLUSIONS: In assessment of cardiovascular collapse induced by stereoisomers of bupivacaine, monitoring with only MAP can lead to misinterpretation and invasive monitoring including CO or cSvO2 measurement might be needed.
Anesthesia, General ; Animals ; Bupivacaine* ; Dogs* ; Electrocardiography ; Hemodynamics* ; Plasma ; Stereoisomerism