ABSTRACT
Four interesting sequoiatones stereoisomers (-) were isolated from a wetland soil-derived fungusby chiral HPLC. On the basis of comprehensive NMR and mass analyses, their planar structures were elucidated as the same as that of sequoiatone B. Among them,and(orand) were a pair of enantiomers, andand(orand) were a pair of stereoisomers with epimerization at C-12, which indicated that sequoiatione-type metabolites exist as enantiomers rather than as optically pure compounds in some strains. With the quantum chemical ECD calculations, the absolute configurations of C-8 in-were determined, which is the first report to establish the absolute configuration of C-8 in sequoiatones. However, the absolute configurations of C-12 in sequoiatones are still unsolved.
ABSTRACT
A new method for chiral separation and purity inspection of landiolol hydrochloride and its stereoisomers was developed by ultra-performance convergence chromatography ( UPC2 ) . The mobile phase was the mixture of supercritical CO2 and methanol/n-butyl alcohol/acetonitrile (1:1:1, V/V) plus 0. 5%NH3?H2O. The separation was carried out on the Daicel CHIRALPAK? IF column (150 mm × 4. 6 mm, 3 μm) with a flow rate of 2. 8 mL/min at 50℃ using 223 nm as detection wavelength. Under the optimized experimental conditions, for R,R-stereoisomer, R,S-stereoisomer and S,R-stereoisomer, the detection limits (LOD, S/N=3) were 0. 3, 0. 4 and 0. 3 mg/L, the linear ranges were 2-300 mg/L, 5-300 mg/L and 2-300 mg/L, the recoveries of spike samples were 103. 4%±2. 5%, 91. 8%±2. 5% and 101. 7%±1. 5%, and the injection repeatabilities were 0. 06%, 0. 09% and 0. 08% (n=6), respectively. The experimental results demonstrate that the UPC2-based method can be used for the analysis and determination of landiolol hydrochloride and its stereoisomers.
ABSTRACT
A cold saponification method for determination of 5 lutein stereoisomers in dairy products by high performance liquid chromatography ( HPLC ) was developed. Samples were cold-saponified at room temperature and extracted by n-hexane/petroleum/dichloromethane ( 2: 2: 1 , V/V/V ) . Then 5 lutein stereoisomers were separated on a YMC C30 column with gradient elution using methanol/methyl tert-butyl ether as the mobile phase, and data were acquired by a photodiode array detector at wavelength of 445 nm. The calibration curve was linear in the range of 0 . 127-5 . 082 mg/L with correlation coefficient of 0 . 9999 , and the recoveries were from 96 . 7% to 102 . 2% with the RSDs in the range of 4 . 1%-5 . 4% ( n=6 ) . The limit of detection was 0 . 010 μg/g ( S/N=3 ) , and the limit of quantification was 0 . 030 μg/g ( S/N=10 ) . By presenting results of good accuracy, precision and sensitivity, this method validates its suitability for routine analysis of 5 lutein stereoisomers in dairy products.
ABSTRACT
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.
Subject(s)
Antidepressive Agents , Carbon , Fluoxetine , Pharmacokinetics , Psychotropic Drugs , Stereoisomerism , Venlafaxine HydrochlorideABSTRACT
PURPOSE: 99mTc-HMPAO is a radiopharmaceutical for imaging cerebral blood flow. HMPAO (RR, SS)-4,8- diaza-3,6,6,9-tetramethylundecan-2,10- dione bisoxime) has three stereoismers such as, meso-, d-, and l-HMPAO. Techentium complexes of meso-HMPAO and d,l-HMPAO are known to have different in vivo brain uptakes. In this study, enantiomers of HMPAO (d-HMPAO and l-HMPAO) were separated from d,l-HMPAO. These enantiomers were labeled with 99mTc and the biodistribution studies were performed in mice. MATERIALS AND METHODS: An intermediate imine product was produced from 2,3-butanedione monooxime and 2,2-dimethyl- 1,3-propanediamine (54% yield) and was reduced into a mixture of three isomers (35% yield). The meso-isomer was separated from d,l-mixture by repeated fractional crystallization (11% yield). The d- and l-enantiomers were subsequently separated by co-crystallization with optical isomers of tartaric acid (25% and 5% yield, respectively). Each enantiomeric HMPAO was labeled with 99mTc by reacting with SnCl2 2H2O and 99mTc-pertechnetate. Biodistribution study was performed 1 hr after tail vein injection to ICR mice. RESULTS: Radiochemical purities of each compound were over 80%. In biodistribution study, the brain uptakes of d,l- d- and l-form were 1.34, 1.12 and 1.67% ID/g, respectively. In case of l-Isomer the brain uptake was higher (1.5 fold) than d-isomer. CONCLUSION: We successfully purified each enantiomeric HMPAO. In biodistribution study of stereoismers of 99mTc-HMPAO in mice, l-HMPAO may show better brain image than d,l-HMPAO which was supplied in a commercial kit.