Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D00907 (CET)
 159 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cephalothin sodium (CET-Na) prepared according to the conventional freeze-drying methods is known to easily develop color during storage. Since amorphous CET-Na has been reported to be markedly unstable, the color development is thought to be due to the presence of traces of CET-Na in an amorphous state observed with scanning electron microscopy. Quantitation by use of the powder X-ray diffractometry of such traces of amorphous CET-Na has proved to be of little use. Thermogravimetry (TG) and differential scanning calorimetry (DSC) have demonstrated that the freeze-dried CET-Na by the conventional methods contains three types of CET-Na: amorphous (unstable phase), quasi-crystalline (metastable phase) and crystalline (stable phase). Pyrolysis initiation temperatures of these three types of CET-Na have been demonstrated to become higher in this order. A new parameter for the evaluation of non-crystallinity of CET-Na has been introduced, in which the ratio is calculated from the data of the total weight loss observed through the pyrolysis of both amorphous and quasi-crystalline CET-Na against the total weight loss of all components during the pyrolysis of sample specimen. The ratio thus calculated is defined as "non-crystallinity". This new parameter has successfully been introduced to establish a good correlation to the degree of increasing color intensity with aging of freeze-dried CET-Na.
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PMID:[Non-crystallinity determination by thermal analysis of freeze-dried cephalothin sodium]. 281 57

Cephalothin sodium (CET-Na) in crystals can be obtained by freezing the aqueous solution and subsequent warming at a fixed temperature for facilitating crystallization prior to vacuum application for drying. The product has, however, been found to unavoidably contain traces of the amorphous CET-Na, which causes a rapid color development during storage. By using thermal analysis, differential scanning calorimetry (DSC), electric conductometry, and polarized light cryomicrographic techniques, the solubilities in water, freezing point, eutectic point, and melting behavior of CET-Na in aqueous solution were investigated. The investigation demonstrated that CET-Na in supersaturated aqueous solution is very stable, and that seeding with microcrystalline CET-Na to the supersaturated solution and subsequent cooling of the mixture till its freezing point gives neither any evidence for crystallization nor for growth of the seed crystals. The freeze-drying of CET-Na in the supersaturated solution after seeding has been demonstrated to give crystalline CET-Na containing neither of amorphous nor of quasi-crystalline form.
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PMID:[Crystallization and subsequent freeze-drying of cephalothin sodium by seeding method]. 281 58