Reference

Quantitative thin layer chromatographic estimation of tetracycline antibiotics

Quantitative thin layer chromatographic estimation of tetracycline antibiotics. Ali, Syed Farooq (Kurram Chem. Co., Rawalpindi, Pak.). Pak. J. Sci. Ind. Res., 18(5), 224-6 (English) 1975. CODEN: PSIRAA. DOCUMENT TYPE: Journal CA Section: 64 (Pharmaceutical Analysis) A thin-layer chromatog. method for estn. of tetracyclines consists of developing their hydrochlorides on acid-washed Kieselguhr (made in a slurry of 0.1M EDTA and 5% glycerol) with ClCH2CH2Cl-CHCl3-EtOAc-MeOH (1:1:1:1), followed by CHCl3-EtOAc-Me2CO (2:2:1), and extg. the sepd. spots with HCl-MeOH. NaOH was added to the supernatant obtained after filtration, and absorbance was measured in acid medium at 380 nm, 6 min after addn. of the NaOH. For anhydrotetracycline-HCl [13803-65-1], because of its yellow color, the absorbance was measured directly at 428 nm. The sepn. was good for amts. of tetracyclines ranging 0.1-0.2 mg. For anhydrotetracycline, amts. of .ltoreq.0.05 mg were estd. accurately. The method was better than the earlier-reported comparative absorbance method.

Rate and proposed mechanism of anhydrotetracycline epimerization in acid solution

Rate and proposed mechanism of anhydrotetracycline epimerization in acid solution. Sokoloski, T. D.; Mitscher, L. A.; Yuen, P. H.; Juvarkar, J. V.; Hoener, B. (Coll. Pharm., Ohio State Univ., Columbus, Ohio, USA). J. Pharm. Sci., 66(8), 1159-65 (English) 1977. CODEN: JPMSAE. DOCUMENT TYPE: Journal CA Section: 63 (Pharmaceuticals) The pathway through which the toxic tetracycline (I) [60-54-8] degrdn. product epianhydrotetracycline [7518-17-4] forms in soln. was studied, using high-performance liq. chromatog. and CD, taking advantage of the large difference in ellipticity between the reactant and the product at 285 nm. The epimerization of anhydrotetracycline-HCl (I-HCl) [13803-65-1] followed a reversible 1st-order process, and both anal. methods yielded the same rate consts. The rate consts. indicated that II epimerization was faster than I epimerization. The equil. favored II, and the activation energies for the forward and reverse rates were almost the same as those for I epimerization. The epimerization was catalyzed by phosphate. Activation energies in 0.1 and 1M phosphate were essentially the same. The equil. consts. for both II and I favored the natural configuration rather than the epi series. Possible rationalization based on conformational and H bonding effects is presented.