Die aromatischen Reaktionsprodukte der alkalischen Hydrolyse des Chloramphenicols

Synthesis and Characterization of Benzylidene and Azobenzene Based Photochromic Liquid-Crystalline Polymers

Two series of novel thermotropic main chain liquid crystalline polymers containing photocrosslinkable chalcone and photoisomerizable azobenzene moieties were synthesized from bis[4-( m-hydroxyalkoxy)benzylidene]cycloalkanones [ m = 6,8,10] with 4,4'-azobenzene dicarbonylchloride. The chemical structure of the monomers and polymers were confirmed by spectral techniques. The mesophase properties were investigated using hot stage optical polarized microscopy and differential scanning calorimetry. All the polymers exhibited liquid crystalline properties. The thermogravimetric analysis data revealed that the polymers were stable up to 220 °C and underwent two-stage decomposition. Photocrosslinking property of the polymers was investigated using UV spectroscopy. The cyclopentanone containing polymers showed faster photocrosslinkability than that of their cyclohexanone counterpart. In addition to the photocrosslinkability of cycloalkanone units, the azo moiety displayed E-Z (trans-cis) isomerization in the polymer backbone.

Surface area and crystallinity of Form A of chloramphenicol palmitic and stearic esters: which one is the limiting factor in the enzymatic hydrolysis?

Chloramphenicol stearic and palmitic esters in the polymorphic Form A, when ground for 85 h showed an in-vitro enzymatic hydrolysis rate constant (Khydr), the value of which was the same as that of a commercial Form B. The increase in the rate of the enzymatic hydrolysis was not related to the specific surface area as shown by the fact that the micronized Form A, having a higher specific surface area value than ground Form A, showed the same Khydr as the unground Form A. The Khydr value of the ground Form A could be the result of an increase in the crystalline disorder brought about by the grinding process.

A stability study of chloramphenicol in topical formulations

The stabilities of several chloramphenicol preparations have been investigated at ambient temperatures. The B.P.C ointment and eye ointment were stable over 2 years. The remainder retained more than 90% of their potencies after the following periods: ear drops B.P.C., 2 years, Drug Tariff cream, 5 months and eye drops B.P.C., 3 to 4 months. 15% hydrolysis occurred after autoclaving the eye drops, and 3 to 4% after heating with a bactericide. The latter sterilization process is recommended. Two assay procedures were employed, one estimating residual chloramphenicol by ultraviolet spectrophotometry after separation from decomposition products by thin layer chromatography and the other determining the main degradation product (1-p-nitrophenylpropan-1,3-diol-2-amine) colorimetrically.