Ketones acids, degradation

Methyl ketones are degraded to the next lower carboxylic acid by reaction with hypochlorite or hypobromite ions. The initial step in these reactions involves base-catalyzed halogenation. The a-haloketones are more reactive than their precursors, and rapid halogenation to the trihalo compound results. Trihalomethyl ketones are susceptible to alkaline cleavage because of the inductive stabilization provided by the halogen atoms. 

During a fast, the liver is flooded with fatty acids mobilized from adipose tissue. The resulting elevated hepatic acetyl CoA produced primarily by fatty acid degradation inhibits pyruvate dehydrogenase (see p. 108), and activates pyruvate carboxylase (see p. 117). The oxaloacetate thus produced is used by the liver for gluconeogenesis rather than for the TCA cycle. Therefore, acetyl Co A is channeled into ketone body synthesis. 

When the rate of formation of ketone bodies is greater than the rate of their use, their levels begin to rise in the blood (ketonemia) and eventually in the urine (ketonuria). These two conditions are seen most often in cases of uncontrolled, type 1 (insulin-dependent) diabetes mellitus. In such individuals, high fatty acid degradation produces excessive amounts of acetyl CoA. It also depletes the NAD+ pool and increases the NADH pool, which slows the TCA cycle (see p. 112). This forces the excess acetyl CoA into the ketone body pathway. In diabetic individuals with severe ketosis, urinary excre-... 

MIESCHER DEGRADATION. Adaptation of the Barbier-Wieland carboxylic acid degradation to pcrmil simultaneous elimination of three carbon atoms, as in degradation of the bile acid side chain to the methyl ketone stage. Conversion of the methyl ester of the bile acid to the tertiary alcohol, followed by dehydration, bromination. dehydrohalogenatinn, and oxidation of the diene yields die required degraded ketone. 

Fatty Acid Oxidation Yields Large Amounts of ATP Additional Enzymes Are Required for Oxidation of Unsaturated Fatty Acids in Mitochondria Ketone Bodies Formed in the Liver Are Used for Energy in Other Tissues Summary of Fatty Acid Degradation Biosynthesis of Saturated Fatty Acids... 

The 9/3-configuration has been established " for the fusidic acid degradation product (312). Pimarene (313) was converted through the diazoketone (314) into the mixture of D-nor-compounds (315). Reaction of the 7a-acetoxy-5,10-epoxy-6-ketone (316) with KOH-MeOH gave the ring-B aromatic compound (317) which was subsequently converted into 6,7-diacetoxyequilenin (318). ... 

Fatty acid degradation and synthesis are relatively simple processes that are essentially the reverse of each other. The process of degradation converts an aliphatic compound into a set of activated acetyl units (acetyl CoA) that can be processed by the citric acid cycle (Figure 22.2). An activated fatty acid is oxidized to introduce a double bond the double bond is hydrated to introduce an oxygen the alcohol is oxidized to a ketone and, finally, the four carbon fragment is cleaved by coenzyme A to yield acetyl CoA and a fatty acid chain two carbons shorter. If the fatty acid has an even number of carbon atoms and is saturated, the process is simply repeated until the fatty acid is completely converted into acetyl CoA units. 

In a few instances, not only methyl ketones but other alkyl ketones are degraded to shorter carboxylic acids resulting from halogenation of the methylene group adjacent to the carbonyl and subsequent hydrolysis [103, 160,1172]. The reaction between propiophenone and sodium hypobromite at 22-25 °C gives a 96% yield of benzoic acid [303]. Under similar conditions, 5-butyl-2-butyrylpyridine is converted into 5-butyl-a-picolinic acid in 79% yield [160]. Methyl 3-(a-pyridyl)propyl ketone yields not only the... 

In order to provide further evidence for the presence of the carbonyl in the proposed structure, infrared spectroscopy was performed. The IR spectrum showed a C = O stretch at 1670 cm-1 (consistent with an aryl ketone as in the proposed structure of the acid degradant). The IR and NMR spectral data indicated no significant TFA in the acid degradant isolate. The MS, NMR, and IR data were all consistent with the acid degradant structure proposed. 

Silk fibrion is highly sensitive to oxidising agents like hypochlorite and chlorite solutions. Oxidation and substitution in the benzene ring of tyrosine is responsible for degradation of silk with the formation of chloro-amino acids, ketonic acids and chloramine in several stages [105]. 

Lipid oxidation/degradation of saturated and unsaturated tty acids leads to the formation of many aliphatic hydrocarbons, alcohols, aldehydes, ketones, acids, lactones, 2-alkylfiirans and esters. Other lipid-derived flavors are the benzenoids... 

Under some conditions, fatty acid degradation occurs more rapidly than glycolysis. As a result, a large amount of acetyl CoA is produced from fatty acids, but little oxaloac-etate is generated from pyruvate. When oxaloacetate levels are too low, the excess acetyl CoA is converted to the ketone bodies acetone, acetoacetate, and (3-hydroxybutyrate. 

Depending on their degradative end product, some amino acids can be converted to ketone bodies, some to glucose, and some to both. Thus amino acid degradation is integrated into intermediary metabolism and can be critical to survival under conditions in which amino acids are a significant source of metabolic energy. 

The liver is the major site of amino acid metabolism in the body and the major site of urea synthesis The liver is also the major site of amino acid degradation. Hepatocytes partially oxidize most amino acids, converting the carbon skeleton to glucose, ketone bodies, or CO2. Because ammonia is toxic, the liver converts most of the nitrogen from amino acid degradation to urea, which is excreted in the urine. The nitrogen derived from amino acid catabolism in other tissues is transported to the liver as alanine or glutamine and converted to urea. 

As is well known, the dietary carbohydrates are normally catabolized to give the neutral end products carbon dioxide and water. The intermediately formed organic acids such as lactic acid or tri- and dicarbonic acids of the Krebs cycle solely influence the acid-base balance if they are excreted in their ionic form, leaving behind the protons that would normally be oxidized together with the acidic anion to the neutral end products mentioned above. The same is true for the fatty acids, originating from the dietary fats. Under special circumstances, the fatty acid, degradation leads to the accumulation of ketone bodies. The excretion of acetoacetic and of jS-hydroxybutyric acid in their ionic form results in acidosis, as observed in diabetes. Under normal conditions, however, there is no influence of dietary fat on the acid-base balance. 

During lipid oxidation, the primary oxidation products that are formed by the autoxidation of unsaturated lipids are hydroperoxides, which have little or no direct impact on the sensory properties of foods. However, hydroperoxides are degraded to produce additional radicals which further accelerates the oxidation process and produce secondary oxidation products such as aldehydes, ketones, acids and alcohols, of which some are volatiles with very low sensory thresholds and have potentially significant impact on the sensory properties namely odor and flavor [2, 3]. Sensory analysis of food samples are performed by a panel of semi to highly trained personnel under specific quarantined conditions. Any chemical method used to determine lipid oxidation in food must be closely correlated with a sensory panel because the human nose is the most appropriate detector to monitor the odorants resulting from oxidative and non-oxidative degradation processes. The results obtained from sensory analyses provide the closest approximation to the consumers approach. Sensory analyses of smell and taste has been developed in many studies of edible fats and oils and for fatty food quality estimation [1, 4, 5]. 

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