Tulathromycin is a novel member of the triamilide class of antibiotics that was developed as a safe and effective single-dose treatment of bovine and porcine respiratory disease. An accurate and precise analytical method was developed for the extraction and measurement of tulathromycin in livestock plasma and lung homogenates. Analytes were solid-phase extracted onto a weak cation exchanger after aqueous dilution of samples and addition of heptadeutero-tulathromycin as an internal standard. Following HPLC with a narrow bore C8 column, quantitative detection of tulathromycin was accomplished by monitoring the transition of a doubly charged precursor ion to a singly charged product ion by tandem mass spectrometry using a triple quadrupole mass spectrometer. Procedures were validated for a dynamic range of 0.1 to 25 ng on column. Observed accuracies were between 90 and 110% of nominal and precision (RSD) varying 7% or less. Response and stability experiments showed that deuterated tulathromycin did not parallel the chemical behavior of tulathromycin. Applicability of the method to livestock studies was tested with plasma and lung samples from cattle and swine dosed with tulathromycin at multiple doses. The results demonstrated that the analytical method performed well in a range of sample concentrations spanning over 3 orders of magnitude and provided dose-exposure relationships for cattle and swine.
Malonic acid derivatives undergo unusually mild decarboxylation when treated with N,N'-carbonyldiimidazole (CDI) at room temperature to generate the carbonyl imidazole moiety in high yield, which can be reacted further with a variety of nucleophiles in an efficient one-pot process.
We examined the effects on food intake and plasma fuels of 2,5-anhydro-D-mannitol (2,5-AM; 2-deoxy-D-fructose), a fructose analogue that inhibits hepatocyte gluconeogenesis and glycogenolysis in vitro. 2,5-AM (50-800 mg/kg po) given to rats during the diurnal fast produced a dose-related increase in food intake during the 2 h after administration. A 200-mg/kg dose of 2,5-AM decreased plasma glucose, increased plasma ketone bodies, free fatty acids, and glycerol, and had no effect on triglycerides. Normal and diabetic rats given 2,5-AM (200 mg/kg ip) increased food intake to the same extent. These results suggest that, unlike other substrate analogues that increase food intake, 2,5-AM increases feeding by creating a metabolic state that resembles fasting.
Abstract:As part of continuing studies on the structural features responsible for the intense sweetness of D-fructose, 3-deoxy-D-erythro-hexulose (3-deoxy-D-fructose, 1) was prepared, its solution composition was determined, and its taste was evaluated. In aqueous solution, 3-deoxy-D-fructose exists as a complex mixture of five tautomeric forms in which the P-D-pyranose form is preponderant (52.5% at 22OC) and the a-D-pyranose form is the least abundant (5%). Quite remarkable is the behavior of the open-chain keto form of 1: its content increases from 7.5% at 22"C, to 36% at 82OC, and to 47% at 97OC, making this form the preponderant one at high temperatures. 3-Deoxy-D-fructose was found to be sweet, albeit probably not as sweet as D-fructose. The hydroxyl group at C-3 is thus not an essential function of the glycophore of D-fructose. The significance of this result is discussed in relation to the evidence already available and the divergent theories that have been proposed to explain the origin of the sweet taste of D-fructose.Key words: 3-deoxy-D-erythro-hexulose (3-deoxy-D-fructose), sweetness, solution composition.Resume : La poursuite d'ttudes sur les attributs structuraux responsables pour la douceur intense du D-fructose nous a conduit B prCparer le 3-dCsoxy-D-Prythro-hexulose (3-dCsoxy-D-fructose, I), B determiner sa composition en solution et h Cvaluer son gotit. En solution aqueuse, le 3-dCsoxy-D-fructose existe sous forme d'un mClange complexe de cinq formes tautomkres dans lequel la forme P-D-pyranose est prtpondtrante (52.5% j. 22°C) et la forme a-D-pyranose est la moins abondante (5%). Le comportement de la forme a chalne ouverte ce'to est tout-i-fait remarquable : prtsente i 7.5% i 22"C, sa concentration augmente i 36% i 82°C et i 47% B 97"C, ce qui en fait la forme la plus abondante i haute tempkrature. Le 3-dCsoxy-D-fructose est doux, cependant probablement pas aussi doux que le D-fructose. Le groupement hydroxyle en C-3 apparait ainsi ne pas &tre une fonction essentielle du glycophore du D-fructose. L'importance de ce rtsultat est discutC en relation avec les donnCes dCji disponibles et les thCories divergentes qui ont Ct C proposCes pour expliquer l'origine de la douceur du D-fructose.Mots clPs : 3-dtsoxy-D-e'rythro-hexulose (3-dtsoxy-D-fructose), caractkre sucrt, composition d'une solution.The origin of the intense sweetness of D-fructose, the sweetest of the natural sugars (I), has been the object of much debate (2). While the lipophilic component X of the presumed tripartite AH-B-X glycophore (3) can be attributed to one of the methylene groups (2), the assignment of the hydrogen bond donor (AH) and acceptor (B)-couple remains unresolved. As part of continuing studies on deoxy ketohexoses designed to probe the role of individual hydroxyl groups in the glycophore of D-fructose, we have already shown (4) that the 5-OH group is not essential for the sweet response since 5-deoxy-D-threohexulose (5-deoxy-D-fructose) is nearly as sweet as D-fructose. We have now completed studies on 3-and 4-deoxy...
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