Acetoacetic acid, detection

Like other sulfhydryl-containing compounds, captopril can cause false-positive ketonuria when assessed with the Legal reaction (sodium nitroprusside reacting with acetoacetic acid and possibly with acetone). It has therefore been suggested that in patients with diabetes taking such drugs ketonuria should be assessed with the Acetest (20). Alternatively, a blood ketone test with Acetest and/ or enzymatic detection of beta-hydroxybutyric acid can be performed for confirmation. 

E.40) Butanoic acid, 3-oxo-, acetoacetic acid, acetylacetic acid Present in traces, but not detectable in all coffee samples (Maier, 1988). 

Apart from the symptoms we have already discussed, type 1 diabetics tend to present with another characteristic readily picked up by an alert clinician. Since sugar is not being properly handled, the tissues have to obtain more of their energy from fatty acid oxidation, but the capacity of the Krebs cycle tends also to be impaired, so that in uncontrolled type 1 diabetes there is a pile-up of ketone bodies made by the Uver. This is discussed in more detail in Topic 21. Acetoacetic acid, one of the two major ketone bodies, spontaneously breaks down to acetone, which, being very volatile, is easily lost into the air the patient breathes out. The smell of acetone on the breath is unmistakeable. This should not of course be detectable if the diabetes is well managed. 

Applications. Acetylated cellulose powder is in principle suitable for separation of all lipophilic substances. Separation alone is not enough however the separated substances must be detectable. This fact has been responsible for the relatively modest extent of application of Ac-cellulose layers. They may be recommended for coloured substances and for those which are detectable in UV light. Some examples of use are separation of polynuclear aromatic compounds [31, 309, 357, 599, 600, 755], anthraquinone dyes [768], antioxidants [596], cutin acids [98], sweetening materials [595], rhodanine derivatives of acetoacetic acid and acetone in urine [574] and ketocarboxylic acids [575]. 

A test which is used for the detection of ketone bodies in urine. It is based on the reaction of ferric chloride with acetoacetic acid to give a purple colour. 

Perfusion experiments before oxygenation problems were solved often gave incomplete or misleading information. Embden s work on fatty acid oxidation in liver (see Chapter 7) suggested acetoacetate was a normal metabolite, although in the intact animal free acetoacetate is only detected when glucose oxidation is impaired. 

Between 1906 and 1908 the breakdown of fatty acids to acetone was detected by Embden in perfused livers. Only fatty acids with even numbers of carbon atoms produced this effect. The acetone was postulated to have originated from acetoacetate. For the next 30 years the 6-oxidative route of fatty acid oxidation was generally unchallenged. By 1935-1936 however much more accurate determinations of the yields of acetoacetate per mole of fatty acid consumed (Deuel et al., Jowett and Quastel) indicated convincingly that more than one mole of acetoacetate might be obtained from 6C or 8C fatty acids. (Octanoic acid was often used as a model fatty acid as it is the longest fatty acid which is sufficiently soluble in water at pH 7.0 for experimental purposes.) The possibility had therefore to be entertained that 2C fragments could recondense (MacKay et al. 1942). 

Although sequential B-oxidation from the carboxyl end of fatty acids was believed to be the mechanism for their breakdown, other schemes had been proposed, notably by Hurtley in 1915, who suggested multiple alternate oxidation—this idea was not widely accepted because the probable intermediates, polyketonic or polyunsaturated fatty acids, had never been detected. The abnormally high levels of acetoacetate produced by various liver preparations, however, caused multiple... 

In some poorly controlled diabetic patients the high rate of fatty acid oxidation decreases the mitochondrial NADVNADH concentration ratio so that the 3-hydroxybutyrate/acetoacetate concentration ratio can rise to as high as 15 in the blood. Since a test for ketone bodies in the urine (using Clinistix or similar material) detects only acetoacetate this can result in a serious underestimate of the concentration of ketone bodies in the urine. 

Echinulin.— The mould metabolite echinulin (126) and its relatives have been the subject of some elegant biosynthetic experiments leading to a clear picture of the way they are elaborated." Echinulin has recently been used as a monitor for the stereochemistry involved in the catabolism of leucine to mevalonic acid " label from the leucine was expected at specific sites in the mevalonate-derived iso-prenoid units of (126). In the event, extensive scrambling of label was observed from the two enantiomers of leucine chirally labelled with "C at C-3. Some selectivity in the labelling was detected, which was interpreted as indicating that carriage of label from leucine to mevalonate had occurred via acetoacetate. 

The disorders of isoleucine and valine metabolism are detected in a sequential process that begins with the evaluation of the symptoms and signs displayed by the patient. Clinical chemistry is helpful in the assessment of ketogenesis by urinary tests for ketones or quantification of 3-hydroxybuty-rate and acetoacetate in the blood. The electrolytes and pH may provide evidence of acidosis and it is important to assess the presence or absence of hyperammonemia. Amino acid analysis of the plasma and urine may be helpful. In virtually all instances the definitive diagnosis will come from organic acid analysis of the urine. 

In contrast to mercury cyanide, alkali cyanides are completely converted into alkaK cyanates when warmed with an excess of potassium permanganate with the precipitation of MnOg. The latter and the excess of KMn04 are destroyed by the addition of a drop of hydroxylamine hydrochloride and a drop of 2 iV hydrochloric acid. At this stage, Hg(CN)2 releases hydrogen cyanide which can be detected by the copper ethyl acetoacetate-tetrabase test described on page 348. In this way, starting with a drop of the test solution, 2 y of Hg(CN)2 can be detected in the presence of 500 y of alkali cyanide. 

Why does ordinary ethyl ether react readily with metallic sodium Some esters, ketones, amides, etc, also react. Write the equation for the reaction between sodium and acetoacetic ester. Some high-molecular-weight com- K>unds that are also verj feebly acidic may not dissolve in dilute aqueous alkali. Such compounds are often detected by dissolving in alcohol and adding a little alcoholic sodium ethylate (See Problem 3.) The sodium test is never applied to compounds in Group IV its main use is in differentiating between alcohols and ctliers and, because of the interference by moisture, it is of limited value... 

In the metabolism of L-leucine, the isovaleryl-CoA produced by the oxidative decarboxylation step is further metabolized by a series of enzyme-catalysed steps to acetoacetate and acetyl-CoA and thence into the tricarboxylic acid cycle. Specific enzyme deficiencies at every stage of this metabolic pathway are known and are described in Section 10.3. In contrast, only one disorder of L-isoleucine metabolism subsequent to the oxidative decarboxylation step has been recognized (Section 10.4), and no disorders of the L-valine pathway from isobutyryl-CoA have been described. This may be due to their relative rarity but possibly also to greater difficulty in their detection. The metabolism of valine and leucine is, however, of particular interest in the organic acidurias, since both are major precursors of propionyl-CoA and methylmalonyl-CoA, defects in the metabolism of which lead to propionic acidaemia and methylmalonic aciduria (Chapter 11). 

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