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At least 487 records · Page 27Linked to original sources
PubMed1993

Properties and cost effective method for production of the antitumor agent declauxin from sporulating Penicillium herquei.

Duclauxin, an antitumor agent, was isolated from sporulating Penicillium herquei (ATCC34665) grown on a medium of peanut hulls supplemented with potato starch solution (termed "Gostar"). The medium was inoculated with a sporulating subculture of P. herquei established on a 2% potato starch slurry supplemented with mineral salts. The P. herquei grew as well on Gostar as on an enriched medium. Duclauxin was isolated in crystalline form from Gostar-grown P. herquei. Comparison of costs of duclauxin obtained from inexpensive Gostar versus costly enriched media indicated that Gostar reduces production expenses. Duclauxin was not effective as an antibiotic against certain species of gram-positive and gram-negative bacteria, fungi, and viruses, but a concentration-dependent inhibition of wheat coleoptile growth was observed. Duclauxin was characterized by melting point, optical rotation, IR and NMR spectroscopy, MS and X-ray diffraction.

Antibiotics, Antineoplastic↗
PubMed1993

Optical crystallographic characteristics of some USP drugs.

Optical crystallographic data were determined on a variety of newer USP drugs for which data had not been previously obtained. The ingredients in an unknown sample can be identified by polarized light microscopy by mounting small amounts of the material in successive specific refractive index liquids and determining refractive indices, optic sign, type of extinction, estimated 2V angle, and other optical characteristics for each ingredient present. This information can then be compared with the data listed on known drugs and excipients and all of the ingredients can be identified. To aid in the identification of unknown drugs, optical crystallographic data obtained on 52 of the newer USP drugs are presented.

Crystallography↗
PubMed1994

Determination of enantiomers in ephedrine mixtures by polarimetry.

Enantiomeric purities have been measured with precisions that are equivalent to those obtained from chiral chromatography by a simple ligand substitution reaction into the first coordination sphere of Cu(II)-tartrate complexes. The model systems are binary mixtures of the ephedrines. Ligand exchange reactions are done in bulk aqueous media. The detector is polarimetry. Multivariate regression analyses of optical rotation data measured at five wavelengths are used to prepare calibration and prediction models for binary mixtures of the enantiomers.

Algorithms↗
PubMed2005

Comparative study between the polysaccharide-based chiralcel OJ and chiralcel OD CSPSs in chromatographic enantioseparation of imidazole analogues of fluoxetine and miconazole.

The enantiomeric separation of a series of imidazole analogues of Fluoxetine and Miconazole endowed with potent antifungal activity was performed using cellulose tris(4-methylbenzoate) (Chiralcel OJ) and cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) as chiral stationary phases. Binary mixtures of n-hexane and alcohol as well as pure alcohols (ethanol or 2-propanol) were used as eluents. The enantiomer elution order was monitored by chiroptical detectors based on on-line optical rotation and circular dichroism measurements. For some of the compounds studied very high enantioseparation factor values (alpha > 7) on Chiralcel OJ CSP were observed. In order to study the chiroptical characteristics of the two most biologically active compounds, chromatographic resolutions were carried out on a semipreparative scale. Assignment of the absolute configuration was empirically established by comparing the CD spectra of the separated enantiomers with those obtained from the enantiomers of Miconazole.

Antidepressive Agents, Second-Generation↗
PubMed2006

Analytical and semipreparative resolution of ranolazine enantiomers by liquid chromatography using polysaccharide chiral stationary phases.

Novel HPLC methods were developed for the analytical and semipreparative resolution of new antianginal drug ranolazine enantiomers. Good baseline enantioseparation was achieved using cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC) chiral stationary phases (CSPs) under both normal-phase and polar organic modes. The validation of the analytical methods including linearity, LODs, recovery, and precision, and the semipreparative resolution of ranolazine racemate were carried out using methanol as mobile phase without any basic and acidic additives under polar organic mode, using CDMPC CSPs. At analytical scale, the elution times of both enantiomers were less than 7.5 min at 20 degrees C and 1.0 mL/min, with the separation factor (a) 1.88 and the resolution factor (R(s)) 2.95. At semipreparative scale, about 14.3 mg/h enantiomers could be isolated and elution times of both enantiomers were less than 13 min at 2.0 mL/min. To increase the throughput, the technique of overlapping injections was used. The first eluted enantiomer was isolated with a purity of 99.6% enantiomer excess (e.e.) and > 99.0% yield. The second enantiomer was isolated with a purity of 98.8% e.e. and > 99.0% yield. In addition, optical rotation and circular dichroism spectroscopy of both ranolazine enantiomers isolated were also investigated.

Acetanilides↗
PubMed2005

Quantitative 1H NMR method for the routine spectroscopic determination of enantiomeric purity of active pharmaceutical ingredients fenfluramine, sertraline, and paroxetine.

Determining the enantiomeric purity of chiral therapeutic agents is important in the development of active pharmaceutical ingredients (API). A strategy for determining the enantiomeric purity of three APIs was developed using nuclear magnetic resonance (NMR) and the chiral solvating agent (CSA) 1,1-bi-2-naphthyl (1). While chiral chromatography is widely used to evaluate enantiomeric purity, it can sometimes suffer from tedious sample preparation obviating rapid measurements that are sometimes needed during the manufacture of such agents. The techniques described herein provide comparable enantiomeric purity results with those obtained with traditional chiral HPLC and other published methods for these compounds. Chiral analysis of standard samples of methylbenzylamine enantiomeric mixtures using 1 were found to be quantitative to approximately 1% minor enantiomer. Enantiomeric purity determination by NMR utilizing chiral solvating agents do not require special instrumental techniques, chemical derivatization or standards and is therefore ideally suited for rapid routine analysis. As a result, the technique demonstrated is commonly used in our laboratory as a complementary or alternative method to chiral HPLC or optical rotation measurements for routine determination of enantiomeric purity.

Chemistry, Pharmaceutical↗
PubMed2004

The molecular origin of the thiamine diphosphate-induced spectral bands of ThDP-dependent enzymes.

New and previously published data on a variety of ThDP-dependent enzymes such as baker's yeast transketolase, yeast pyruvate decarboxylase and pyruvate dehydrogenase from pigeon breast muscle, bovine heart, bovine kidney, Neisseria meningitidis and E. coli show their spectral sensitivity to ThDP binding. Although ThDP-induced spectral changes are different for different enzymes, their universal origin is suggested as being caused by the intrinsic absorption of the pyrimidine ring of ThDP, bound in different tautomeric forms with different enzymes. Non-enzymatic models with pyrimidine-like compounds indicate that the specific protein environment of the aminopyrimidine ring of ThDP determines its tautomeric form and therefore the changeable features of the inducible effect. A polar environment causes the prevalence of the aminopyrimidine tautomeric form (short wavelength region is affected). For stabilization of the iminopyrimidine tautomeric form (both short- and long-wavelength regions are affected) two factors appear essential: (i) a nonpolar environment and (ii) a conservative carboxyl group of a specific glutamate residue interacting with the N1' atom of the aminopyrimidine ring. The two types of optical effect depend in a different way upon the pH, in full accordance with the hypothesis tested. From these studies it is concluded that the inducible optical rotation results from interaction of the aminopyrimidine ring with its asymmetric environment and is defined by the protonation state of N1' and the 4'-nitrogen.

Animals↗
PubMed2001

Synthesis, conformation and biological activity of linear and cyclic Thr6-bradykinin analogues containing N-benzylglycine in place of phenylalanine.

Three linear Thr6-bradykinin analogues in which either one or both the two phenylalanine residues in the peptide sequence have been substituted by N-benzylglycine (BzlGly) and their head-to-tail cyclic analogues were synthesized and tested on an isolated rat duodenum preparation. The linear (BzlGly5,Thr6-BK, BzlGly8,Thr6-BK and BzlGly(5,8),Thr6-BK) and the cyclic (cyclo BzlGly5,Thr6-BK, cyclo BzlGly8,Thr6-BK and cyclo BzlGly(5,8),Thr6-BK) peptoid-like analogues were characterized by amino acid analysis, optical rotation, analytical HPLC and MALDI-TOF mass spectroscopy. The conformational features of both the linear and cyclic derivatives were investigated by FT-IR and CD measurements. Preliminary molecular mechanics calculations were also performed on some synthetic peptides. Pharmacological screening using the relaxation of the isolated rat duodenum preparation showed that incorporation of N-benzylglycine at positions 5 and/or 8 in the linear Thr6-BK causes a substantial decrease in potency. Comparable incorporation in cyclo Thr6-BK, at position 8, or 5 and 8, resulted in nearly inactive analogues. However, cyclo BzlGly5,Thr6-BK showed a potency which is of the same order of magnitude as for cyclo-BK and cyclo Thr6-BK.

Bradykinin↗
PubMed2002

Carbohydrate analysis of bacterial polysaccharides by high-pH anion-exchange chromatography and online polarimetric determination of absolute configuration.

A significant problem in structure determination of complex carbohydrates, especially for bacterial polysaccharides, is determination of the absolute configuration of the component monosaccharides. A number of analytical methods have been used for this purpose but, as a result of the wide variety of chemical properties of sugars found in complex polysaccharides, no single method is universally applicable. High-resolution gas chromatography of volatile derivatives with chiral reagents is the most widely used method. Optical activity, although direct and simple, lacks sensitivity generally requiring a large quantity of pure monosaccharide. We report a combination of high-performance anion-exchange chromatography (HPAEC) with combined electrochemical pulsed amperometric detection and in-line detection of optical rotation with an in-line laser polarimeter for analysis of a number of sugars found in complex polysaccharides. We show that application of the method for analysis of capsular polysaccharides of several gram-positive and gram-negative pathogenic bacteria provides useful information simultaneously on carbohydrate composition and the enantiomeric configuration of component sugars.

Bacteria↗
PubMed1993

Isolation and characterization of (+)-1,1a-dihydroxy-1-hydrofluoren-9-one formed by angular dioxygenation in the bacterial catabolism of fluorene.

Transformation of fluorene by washed cells of fluorene-grown Pseudomonas sp. F274 yielded 1,la-dihydroxy-1-hydrofluoren-9-one (up to 100 mg/l) as the stable product of angular dioxygenation of 9-fluorenone. Structural identity of the angular keto-diol was established by 13C- and 1H-NMR, gas chromatography- and direct probe-mass spectrometry. Definitive assignment of 1,1a-dioxygenation, but not 4,4a-, was based on the isolation and rigorous identification of 1-hydroxyfluoren-9-one as the exclusive product of acidic dehydration. Chiral 1H-NMR analysis and optical rotation of isolated 1,1a-dihydroxy-1-hydrofluoren-9-one ([alpha]D = + 132.1 degrees) are indicative of a single enantiomer with an inferred cis-stereochemistry of the hydroxyl groups. This compound is evidently an intermediate of fluorene catabolism by this strain and not a dead-end product because its formation is transient in washed cell incubations and ultimately it is completely consumed with the formation of acidic metabolites.

Fluorenes↗
PubMed1977

An alkali-soluble polysaccharide from the cell walls of Coprinus lagopus.

An alkali-soluble polysaccharide was isolated from the purified mycelial walls of Coprinus lagopus. The hydrolysis products, optical rotation, and infrared spectrum indicate a beta-glucan. Hydrolysis of the glucan after permethylation gave only 2,3,4,6-tetra-, 2,4,6-tri-, and 2,4-di-O-methyl-D-glucose. These methylated sugars and their relative quantities reveal that the glucan is a polysaccharide containing beta-1,3-linked glucose units with about 14% of the sugars having 1,6-linked branch points. Partial hydrolysis of the product derived from Smith degradation of the glucan released laminaribiose and gentiobiose suggesting that the branches are generally longer than a single glucose unit.

Agaricales↗
PubMed1983

Conservation of physico-chemical amino acid properties during the evolution of proteins.

Based on a similarity ring constructed from a substitution probability matrix, we have analyzed the conservation of some amino acid properties in the evolution of proteins. Refractive index and bulkiness are highly conserved, hydrophobicity and polarity are fairly well conserved while optical rotation appears to be a less relevant property. On the other hand, the analysis of the correspondence between phenotype and genotype shows that the most frequent amino acid substitutions in proteins do not always correspond to the most feasible codon changes. The apparent disagreement between amino acid substitutions in modern proteins and the primordial amino acid-codon assignment is discussed.

Amino Acids↗
PubMedDate not supplied

Experiments of the origins of optical activity.

Two recent reports claim that (1) aqueous L-aspartic acid polymerizes faster than D-Asp in the presence of kaolin at 90 degrees, and (2) L-phenylalanine is adsorbed by kaolin more extensively than D-Phe at pH 4(the reverse being true at pH2). The novelty of these observations and their potential significance for the origin of optical activity has prompted us to duplicate these experiments using more sensitive methods. L- and D, L-Asp in 0.01 M solution were incubated with kaolin at 90 degrees for 8 days. Careful examination of the aqueous residues from such experiments failed to demonstrate any preferential polymerization of L-Asp over D-Asp, or indeed any significant gross polymerization of Asp at all. In other experiments 0.001 M solutions of D, L-Phe at pH 6 and pH 2 were stirred with large excesses of kaolin for 24 hr, and the aqueous extracts from these mixtures were examined for gross adsorption using the amino acid analyzer. No significant gross adsorption was noted. We then looked for asymmetric adsorption in the aqueous residues using optical rotatory dispersion, gas chromatography and thin layer chromatography. By none of these analytical criteria could we find any evidence whatsoever for the preferential adsorption of D- versus L-Phe from either pH 6 or pH 2 solutions. Finally, in experiments bearing on the origin of optical activity by parity violation during beta-decay, we have irradiated solid samples of D-, L- and D,L-leucine in a 61700 Ci Sr-90 source at Oak Ridge National Lab. for 1.34 yr (total dose: 4.2 x 10(8) rad). Gas chromatographic examination of the (appropriately derivitized) recovered samples showed that the L-Leu was 16.7% decomposed, the D-Leu 11.4% and theD,L-Leu 13.8% decomposed. The recovered D,L-Leu sample had a gas-chromatographically determined enantiomeric composition of 50.8% D-leu and 49.2% L-Leu. These data, though very close to experimental error, may indicate a slight preferential radiolysis of L-Leu compared to D-Leu by the Bremsstrahlung from Sr-90 beta-decay. These high intensity irradiation experiments are being continued on a prolonged basis in order to reach more definitive conclusions.

Adsorption↗
PubMed1996

Enantioselective autocatalysis. IV. Implications for parity violation effects.

Historically, parity violation at the contemporary biomolecular level (i.e., only L-amino acids in proteins and D-sugars in DNA and RNA) has been postulated to be the inevitable result of parity violations at the elementary particle level, involving either beta-decay electrons or parity violating energy differences (PVEDs) between enantiomers. These two chiral biases have in turn allegedly impressed a small but persistent chirality onto prebiotic chemistry which, after appropriate amplification, has culminated in our contemporary homochiral biopolymers. Experiments and controversies pertaining to the efficacy of these two chiral biases are reviewed briefly, with the conclusions that: a) there is no experimental evidence supporting the capability of beta-decay electrons or other spin-polarized chiral particles to generate chiral molecules, and b) only theoretical calculations, but no experimental evidence, support the allegation of a causal relation between PVEDs and biomolecular homochirality. We here attempt to examine the latter allegation experimentally. Spontaneous resolution under racemization conditions (SRURC) during the crystallization of the bromofluoro-1,4-benzodiazepinooxazole derivative I is capable of affording products of high enantiomeric purity. This process, which involves very efficient stereoselective autocatalysis, has now been examined statistically. If PVED effects are operative, the SRURC of racemic I should provide, either exclusively or with a strong and consistent bias, only one enantiomer of crystalline I. However, crystallization experiments of racemic I showed no bias in its SRURC, leading to the conclusion that PVED effects are ineffective in dictating a preferred chirality in this system. Several earlier experiments in the literature leading to a similar conclusion as to the inefficacy of PVED effects in promoting a preferred chirality are noted.

Amino Acids↗