Methionine Substitutes in Ruminant Nutrition I: Stability of Nitrogenous Compounds Related to Methionine during In Vitro Incubation with Rumen Microorganisms

Abstract

4:1:2)] were scraped off, eluted into n-hexane, back-extracted into the ceric sulfate-sulfuric acid solution, and examined by the oxidation-UV method. The resulting UV absorption spectra from both the unchanged methadone and the metabolite were identical to that of benzophenone. GLC examination of the heptane following reflux further substantiated that benzophenone was formed from both the parent drug and the metabolite. DISCUSSIONThe extended linearity of the spectrophotometric method permits the use of a single aliquot of the specimen to encompass most urine methadone concentrations encountered in patients receiving methadone maintenance. Analysis by the barium peroxide method required varying specimen volumes since linearity was achieved up to a concentration of 25 pg/ml.A comparison of the procedures and results of the ceric sulfate and barium peroxide methods indicates several advantages of the former in addition to the extended linearity and elimination of the required alkaline wash. Oxidation of methadone by the method of this report gives a 84.6 f 3.2% yield of benzophenone as opposed to a 77.8 f 3.3% yield obtained with the barium peroxide method. In addition to the time saved through the elimination of an extraction step, the proposed spectrophotometric method requires a shorter reaction time; e.g., 20 min reflux with barium peroxide provided only a 48% yield of benzophenone compared to an 82% yield obtained with ceric sulfate. Additionally, reflux conditions were less critical since no significant change in percent yield was observed as the amount of primary oxidant was varied from 200 to 300 mg, the molarity of the sulfuric acid was varied from 5 to 6, or the duration of reflux was varied from 25 to 50 min. Similar variations in the barium peroxide method resulted in significantly decreased yields; changes in the amount of acid, solvent, and heat of reflux produced similar effects in both methods.The proposed methods provide rapid and sensitive quantitative methods for determining methadone a t therapeutic levels in biological specimens. Since other diphenyl-substituted drugs are susceptible to cerium sulfate, utilization of the GLC technique in conjunction with the spectrophotometric method provides a highly specific analytical methodology for methadone in biological specimens. The methods are particularly useful as a quantitative test in suspected methadone overdose cases and as a mechanism to monitor pharmacokinetic studies. In methadone maintenance programs the techniques can be used in collaboration with TLC to confirm on a relative basis that patients are receiving, within broad limits, proper dosages of the drug.Abstract Thirty-one nitrogenous compounds with possible methionine activity were included as potential nitrogen sources in media for in uitro incubation of rumen microorganisms. Compounds not supporting cellulose digestion were included in studies of ammonia release and specific analyses designed to confirm resistance of the compounds to microbial deamination. N-Acetyl-DLmethionine (IV)...