Separation of novel derivatives from commercial erythromycin samples by thin-layer chromatography.
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Chromatography, Thin Layer↗
Biomedical subjects
E Roets
Publications and source records attributed to E Roets.
Quantitative determination by high-performance liquid chromatography of acetylsalicylic acid and related substances in tablets.
High-performance liquid chromatography on a Zorbax C8 7-micron column (25 cm X 0.46 cm I.D.) with methanol-water-1 M phosphoric acid (59:36:5) as the mobile phase has been used for the analysis of several naturally aged batches of fourteen brands of acetylsalicyclic acid tablets. The extraction solvent is methanol, containing 2% v/v of formic acid. Salicylic acid is the main impurity. Acetylsalicylsalicylic acid is the second most important impurity, and the corresponding salicylsalicylic acid is rarely present. Buffered or dispersible tablets contain relatively more of the latter two impurities and eventually also the corresponding higher oligomers. Acetylsalicylic anhydride is always a minor impurity. Comparison is made with classical spectrophotometric methods, which are observed to be selective for salicylic acid.
Aspirin↗
Isolation of bovine lymphocytes for beta 2-adrenoceptor determination by means of the radioligand technique: some practical implications.
The present investigation was undertaken to demonstrate saturable beta 2-adrenoceptor binding sites on cell membranes of bovine lymphocytes by means of the non-selective antagonist (3H)dihydroalprenolol. Although the classical density gradient centrifugation technique was used as described for the isolation of these cells from human blood, striking differences in binding characteristics were observed. It is suggested that differences in physical properties of blood might be responsible for these phenomena. Since receptor density and affinity of beta 2-adrenoceptors in lymphocytes are used in human medicine (and will be in the future in veterinary medicine) for correlation with several physiological and pathophysiological conditions, attention is drawn to the effect of dilution of blood during the preparation of these cells; in lactating cows, the best results were obtained with the dilution 1:0.5.
Adult↗
[Radioligand identification and characterization of alpha- and beta-adrenoceptors in udder tissue of lactating cows].
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Animals↗
Analysis of a complex analgesic formulation by high-performance liquid chromatography with column-switching.
An isocratic method is described which allows the complete separation of acetylsalicylic acid, paracetamol, caffeine, carbromal, bromisoval and codeine as well as the potential impurities salicylic acid, diacetyl-p-aminophenol and acetylcodeine. A column-switching technique was developed employing two columns (10 cm and 25 cm) containing 7-microm Zorbax C(8) material. The separation is better and faster than that obtained with a gradient elution method.
Journal Article↗
Effects of valerate and isobutyrate on fatty acid secretion by the isolated perfused mammary gland of the lactating goat.
The isolated mammary glands of six lactating goats were perfused with heparinized and oxygenated blood for 8 to 11 h. Adequate quantities of glucose, acetate and amino acids (including valine) were added to the perfusate. Either unlabelled valerate or unlabelled isobutyrate was added in excess to the perfusate of one gland, while the respective symmetrical gland was used as a control. After the administration of valerate, the proportions of the odd-numbered fatty acids (C11:0, C13:0, C15:0) in the milk fat, collected every hour during perfusion, rose progressively after 5 h until the end. The synthesis of milk fatty acids from valerate is discussed. After isobutyrate was added to the perfusate, isoC12:O, isoC14:0 and isoC16:0 in the milk fat increased as compared to the control. The effect of isobutyrate indicated that valine acted as a precursor of milk iso-branched fatty acids after its metabolisation to isobutyryl-CoA. During perfusion in the presence of the complete substrate mixture, the proportion of certain major milk fatty acids (C10:0, C12:0, C14:0 and C16:0) increased, whereas the proportion of C18:0 and C18:1 decreased. These effects have been ascribed to the presence of acetate and beta-hydroxybutyrate in the substrate mixture.
Animals↗
Relationship between milkability and adrenoceptor concentrations in teat tissue in primiparous cows.
Milking characteristics were measured on 19 primiparous cows of the Red Pied breed at morning milkings. Measurements included maximum and average rate of flow, yield of milk through the 1st, 2nd, and 3rd min, amount of milk through the first 2 and first 3 min of milking, and milking time. Subsequently cows were slaughtered and teats immediately removed. Adrenoceptors on membranes isolated from teat tissue were identified by radiolabeled antagonists: [3H]dihydroalprenolol for beta 2-adrenoceptors, [3H]rauwolscine for alpha 2-adrenoceptors, and [3H]prazosin for alpha 1-adrenoceptors. Measurements of milking characteristics were highly repeatable within cow. Cows showed five distinct and significantly different milk flow patterns, which were characteristic for fast (type I, II), relatively fast (type III), and slow (type IV, V) milking cows. Covariance analysis for the five different types revealed an average regression between alpha 2-adrenoceptor density and milking rate 1st min as well as between beta 2:alpha 2-adrenoceptor ratios and milking rate 2nd min and milking time. A hypothesis is presented to explain these observations. During milking, tone of efferent sympathetic nerves in the teat is low. This phenomenon is more pronounced in fast milking cows. The typical presynaptic adrenoceptor pattern in the teat of fast milkers (low beta 2:alpha 2-adrenoceptor ratio) results in a decline of norepinephrine release by feedback mechanisms.
Animals↗
A comparison of the binding characteristics of the alpha 2-adrenoceptor antagonists 3H-yohimbine and 3H-rauwolscine in bovine teat muscles.
3H-Yohimbine and 3H-rauwolscine, both potent and selective alpha 2-adrenergic antagonists, were used to identify alpha 2-adrenoceptors in smooth muscles of the cistern wall of teats of lactating cows. Binding of these radioligands was rapid and readily reversed by 10 microM phentolamine. Saturation experiments in the presence of 3H-yohimbine showed an equilibrium KD value of 6.23 +/- 0.74 nM and a maximum number of sites of 81 +/- 7 fmol/mg of membrane protein. In the presence of 3H-rauwolscine, however, a higher density of alpha 2-receptors (164 +/- 12 fmol/mg protein) with a KD of 6.16 +/- 0.64 nM was found. No cooperative interactions among both binding sites were observed. Both 3H-yohimbine and 3H-rauwolscine binding sites showed alpha 2-adrenergic specificity. On the basis of its higher affinity to the alpha 2-adrenoceptor sites, better ratio of specific to non-specific binding and for other reasons, 3H-rauwolscine appears to be the ligand of choice.
Adrenergic alpha-Agonists↗
Separation of erythromycin and related substances by high-performance liquid chromatography on poly(styrene-divinylbenzene) packing materials.
A comparative evaluation of three brands of poly(styrene-divinylbenzene) copolymers, Hamilton PRP-1 (10 micron), Rogel (8 micron) and TSK-Gel (10 micron), as column packing materials for high-performance liquid chromatographic separation of erythromycins is presented. Erythromycins A, B and C, anhydroerythromycin A, erythromycin A enol ether, N-demethylerythromycin A, anhydro N-demethylerythromycin A and N-demethylerythromycin A enol ether were chromatographed. The effects of column temperature, concentration of organic modifier in the mobile phase, concentration of phosphate buffer, the addition of quaternary ammonium salts and pH are described. The best separations were obtained on TSK-Gel with the mobile phase acetonitrile-methanol-0.2 M tetramethylammonium hydroxide pH 8.0-0.2 M phosphate buffer pH 8.0-water (30:15:25:5:25). PRP-1 and Rogel gave equally good separations but with higher retention volumes.
Animals↗
Determination of the stability of tetracycline suspensions by high performance liquid chromatography.
High performance liquid chromatography was used to examine the stability of tetracycline suspensions, prepared according to the Formulary of the Dutch Pharmacists and the National Formulary v (Belgium). The influence of the nature of the buffer salt, of the pH, and of the temperature and time of storage are discussed. At slightly acid pH (4 to 5.5) and at room temperature suspensions are stable for at least three months.
Chromatography, High Pressure Liquid↗
Quantitative determination of amoxicillin and its decomposition products by high-performance liquid chromatography.
Amoxicillin, amoxicilloates, amoxicillin oligomers and amoxicillin piperazine-2,5-dione are separated by reversed-phase (C8) high-performance liquid chromatography with gradient elution. Quantitative results are reported for a number of samples. Amoxicillin trihydrate samples mostly contain amoxicilloate as the main impurity. Samples of the sodium salt also contain the piperazine-2,5-dione and the dimer. Higher oligomers such as the trimer and tetramer were not present in significant amounts. Several samples were also analysed by a mercurimetric titration method.
Amoxicillin↗
Antibacterial activities of erythromycins A, B, C, and D and some of their derivatives.
The MICs of erythromycins A, B, C, and D and some of their derivatives were determined against 21 gram-positive and 15 gram-negative microorganisms. Antibacterial activity was confined to gram-positive and very few gram-negative bacteria. Erythromycin B was somewhat less active than erythromycin A, and erythromycin C and D showed about half that activity or even less. Most other derivatives had negligible activity. Determination of potency by diffusion and turbidimetric assays were in line with MICs. The examination of the results of these assays, however, revealed that there are differences between the data of different laboratories, depending on the microorganisms and conditions used.
Bacteria↗
Synthesis of deuterium- and tritium-labeled 6 beta-bromopenicillanic acid.
The synthesis of 6 beta-bromopenicillanic acid labeled with deuterium and tritium in the beta-methyl group is described. The S-sulfoxide of benzyl- or p-methoxybenzyl 6 alpha-bromopenicillanate is refluxed in benzene containing an excess of tert-BuOD, D2O or HTO. After deoxygenation and deprotection of the ester, the labeled 6 alpha-bromopenicillanic acid is epimerized (N,O-bis(trimethylsilyl)acetamide/1,5-diazabicyclo[4.3.0]non-5-ene in CH2Cl2). The two epimers are separated by column chromatography.
Chemical Phenomena↗
Homogeneity of beta-adrenoceptors on bovine teat muscles.
Bovine teat beta-adrenergic receptors were investigated with binding studies using 3H-dihydroalprenolol (DHA) as ligand. Inhibition of 3H-DHA-binding by beta 1-(betaxolol, atenolol, practolol) and beta 2-(zinterol, fenoterol, ICI 118551) selective drugs resulted in monophasic displacement curves with Hill coefficients close to 1.0. Computer assisted analysis of these curves did not reveal the presence of more than one class of binding sites. These data suggest that the beta-receptor sites present in bovine teat walls are of the beta 2-subclass.
Adrenergic beta-Antagonists↗
Identification and characterization of 3H-prazosin binding to alpha 1-adrenoceptors in bovine teat muscles.
The highly specific alpha 1-adrenoceptor antagonist 3H-prazosin was used to characterize alpha 1-adrenoceptors in smooth muscles of the cistern wall of teats of lactating cows. Binding was rapid, readily reversible, stereospecific and saturable. Scatchard analysis of saturation binding data on bovine teat membranes revealed that 3H-prazosin bound to a single class (Bmax = 128 +/- 13 fmol/mg of membrane protein) of noncooperative sites (Hill coefficient = 0.95 +/- 0.02) with high affinity (KD = 0.47 +/- 0.05 nM). Competition binding studies with 9 antagonists and 8 agonists, indicated that 3H-prazosin labeled the alpha 1-receptor.
Animals↗
Analysis of tablets containing aspirin, acetaminophen, and ascorbic acid by high-performance liquid chromatography.
The high-performance liquid chromatographic method described enables the quantitation of the components and the main impurities of tablets containing aspirin, acetaminophen, and ascorbic acid. A C8 reverse-phase column was used; the mobile phase was methanol-0.2 M phosphate buffer (pH 3.5)-water (20:10:70). Results obtained for a brand of effervescent tablets, normally aged for 5 years and stressed at 37 degrees C, 50 degrees C, or in 79% relative humidity at room temperature, are reported. Salicylic acid was the main product of decomposition. Diacetyl-p-aminophenol was observed to be formed by transacetylation.
Acetaminophen↗
Analysis of tablets containing acetylsalicylic acid and phenylephrine by high-performance liquid chromatography.
A high-performance liquid chromatographic method permitted the quantitation of acetylsalicylic acid, phenylephrine, caffeine and phenacetin in tablets, and of the main impurities, salicylic acid and mono- and diacetyl derivatives of phenylephrine. A C8 reversed-phase column was used with a mobile phase containing methanol-1 M phosphoric acid-water 34:5:61 v/v/v.
Journal Article↗
Identification of beta-adrenoceptors in bovine teat muscles by 3H-dihydroalprenolol binding.
beta-Adrenoceptors present in smooth muscles of the cistern wall of teats of lactating cows were identified and characterized by 3H-dihydroalprenolol (DHA) binding. Binding association and dissociation at 37 degrees C were very rapid (t1/2 amounting to 2 min and 1 min 30 sec respectively), stereospecific and saturable. By Scatchard analysis, the mean receptor density was 92 fmol of 3H-dihydroalprenolol bound/mg protein and the dissociation constant was 0.63 nM. The Hill number was 1.01. The order of potency of catecholamines for the binding was (-)-isoproterenol greater than (-)-epinephrine greater than (-)-norepinephrine, indicating a population of mainly beta 2-adrenoceptors. Potency series of 10 antagonists and 15 agonists, determined from binding-inhibition experiments, were composed.
Alprenolol↗