3- Isobutyl-l-methylxanthine

Isobutyl-l-methylxanthine (3-isobutyl-l-methylpurine-2,6-dione) [28822-58-4] M 222.3, m 199-210°, 202-203°, pK ,t 6.7 (acidic NH). Recrystd from aqueous EtOH. 

Ia+ Murine class II major histocompatibility complex antigen IB4 Anti-CD 18 monoclonal antibody IBD Inflammatory bowel disease IBMX 3-isobutyl-l-methylxanthine IBS Inflammatory bowel syndrome iC3 Inactivated C3 iC4 Inactivated C4 IC50 Concentration producing 50% inhibition... 

Least et al. reduced the sample size to 20 pi serum, plasma, or saliva, in a microscale procedure. The extraction was carried out with a chloroform-isopropanol solution of the internal standard, 3-isobutyl-l-methylxanthine. After alkylation with tetramethylammonium hydroxide and pentyl iodide, gas chromatography was carried out on a packed 3 OV-17 on Gas Chrom Q column, by temperature programming from 180°C to 260°C, and using a nitrogen sensitive detector. With the sample volume used, the background interference is equivalent to about 0.1 mg/litre, and 0.5 mg theophylline per litre can easily be measured. Between-run... 

To improve the theophylline analysis, Bailey et al. used 3-isobutyl-l-methylxanthine as... 

Schwertner et al. introduced a salting-out procedure, in combination with single extraction using chloroform-isopropanol (95 5). 100 pi plasma samples could be effectively extracted with 2 ml chloroform-isopropanol. Theophylline was derivatized with pentafluoroben-zyl chloride, and 3-isobutyl-l-methylxanthine was used as an internal standard. This standard is similar to theophylline in extractability, derivatization rates, stability and chromatographic properties. Accurate measurements of plasma concentrations ( + 0.22 ug/ml) could be obtained with little or no interference from theophylline metabolites and other coextract-able material. A packed column with 3 OV-17 on Gas Chrom Q and temperature programming from 150°C to 250°C was used in combination with an electron capture detector. 

Solutions of drugs were prepared in 145 mM aqueous NaCl, from which a dose series was prepared. dl-Octopamine, dl-synephrine, dopamine, tolazoline, clonidine, yohimbine, cyproheptadine, gramine, chlorpromazine, promethazine, propranolol, metoclopramide, and 3-isobutyl-l-methylxanthine were obtained from Sigma Chemical Co. naphazoline from Aldrich Chemical Co. chlordimeform and phentolamine from Ciba Geigy mianserin from Research Biochemicals Inc. and lofexidine, XAMI, and tramazoline were gifts from Dr. R. Hollingworth, Purdue Univ. 

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