8-Hydroxy saturated fatty acids

A series of 8-hydroxy saturated fatty acids were synthesized to explore the effect of chain length on activity. The hydroxyl function was maintained on the eight carbon by starting with 1,8-octanediol and the chain length dictated by a reaction with the appropriate carbon number saturated Grignard reagent. The eighteen carbon 8-hydroxy compound demonstrates the most activity in this series (Fig. 5). 

Another class of lipid components formed by heating which contribute to meat flavor is the lactones, which are formed by the lac-tonization of y- and 6-hydroxy fatty acids. 6-Long chain (6-tetra-decalactone) lactones predominate. Lactones can also be formed by conversion of low molecular weight saturated fatty acids, aldehydes and alcohols during heating of meat fat (13). Larick et al. (14) found Cla-Ci, 6-lactones associated with more desirable flavor of beef... 

Chemistry and general properties. The product is prepared by reacting a fatty acid, typically oleic acid (a 08 1 acid), with oleum, or preferably sulphur trioxide. If a saturated fatty acid is used, the product is an a-sulphofatty acid, R(S03H)C00H and the reaction mechanism is thought to be similar to that previously suggested for the sulphonation of methyl esters. With the use of an unsaturated acid, such as oleic, the picture becomes more complex. The reaction chemistry is not fully understood, but the product is a mixture of y-hydroxy sulpho fatty acid and o -sulphonated oleic acid. 

A series of compounds were synthesized by the coupling of the appropriate diol and Grignard reagents to determine if the position of hydroxylation is a determinant of activity on C-18 saturated fatty acids. Our bioassay shows a strict requirement of the 8-hydroxy position for activity (Fig. 6). 

Fatty acid distributions can be affected by microbial oxidation in sediments, so care must be exercised when certain components are used as source indicators. For example, (3-hydroxy fatty acids are produced from (3-oxidation of saturated fatty acids. In addition, C0-oxidation of saturated fatty acids to CO-hydroxy acids and of CO-hydroxy acids to a,CO-diacids is performed by yeasts (unicellular fungi, mainly belonging to the as-comycetes) and bacteria. Consequently, while the long-chain (>C22) CO-hydroxy acids are reliable indicators of higher plant sources, the short-chain components... 

BHT butylated hydroxy toluene LS low-saturated fatty acid soybean... 

Apart from saturated fatty acids, Simoneit and Mazurek (1982) observed low concentrations of unsaturated fatty acids (range C,4-Ci7) a-hydroxy fatty acids (range C 0-C24) that are known components of grass wax dicarboxylic acids (range C 0-C24) that probably arise from the direct biodegradation of hydroxy fatty acids and diterpenoidal acids occurring as diagenetic products of diterpenoids from coniferous resins. 

Previously, the strain DS5 bioconversion products from oleic and linoleic acids were identified as 10-ketostearic (23) and 10-hydroxy-12(Z)-octadecenoic acid(24), respectively. It is interesting to find that all unsaturated fatty acids tested are hydrated at the 9,10 positions with the oxygen functionality at C-10 despite their varying degree of unsaturations. DS5 hydratase was not active on saturated fatty acids and other non-9(Z)-unsaturated fatty acids such as elaidic [9(.B)-octadecenoic], arachidonic [5( ),8( ),1 l( ),14( )-eicosatetraenoic], and erucic [13( )-docosenoic] acids (25). From all of the data gathered, it is concluded fliat DS5 hydratase is indeed a C-10 positional-specific enzyme. The fact that elaidic acid was not hydrated indicates that die unsaturation must be in flie cis configuration for DS5 hydratase activity. 

The Type II synthetase of E.coli was the first synthetase studied. The individual proteins have all been isolated, purified and characterized (cf. Volpe and Vagelos, 1973). The synthetase cannot only produce saturated fatty acids but normally makes monounsaturated (principally cw-vaccenic) acids. It does this because of the presence of a -hydroxy-decanoyl-ACP-/3,y-dehydrase which produces cw-3-decenoyl-ACP (precursor of unsaturated acids) instead of ran -2-decenoyl-ACP (converted to saturated acids). The presence of the two de-hydrase enzymes forms a branch point at the Cio level when only the ran5-2-decenoyl-ACP acts as a substrate for enoylreductase. The a 5-3-isomer can be condensed by /3-ketoacyl synthetase so that the double bond is preserved and the production of unsaturated fatty acids is anaerobic (Volpe and Vagelos, 1973). 

Cerebrosides differ also in the composition of the constituent fatty acids. Alpha-hydroxy fatty acids with chain lengths ranging between 18 and 25 carbon atoms have been obtained from cerebroside hydrolysates. The saturated fatty acids most frequently found are stearic and lignoceric acids. The unsaturated fatty acids found mainly in cerebroside hydrolysates are 24 carbons long. Sphingosine is present in 95% of the cerebrosides, but cerebrosides containing dihydro-sphingosine have also been reported. 

Hydroxylation of nonactivated sp -hybridized carbon atoms belongs to the classical oxidative reactions catalyzed by P450s. Examples of this reaction include the hydroxylation of saturated fatty acids (8) to hydroxy fatty acids (9) catalyzed, for example, by eukaryotic CYP4 and bacterial CYP102 enzymes [58], as well as the stereospecific hydroxylation of D-( + )-camphor (10) to 5-exo-hydroxycamphor (11) through P450<-am [59] (Scheme 12.2). 

Chemical synthesis of the palmitoyl- and stearoyl-derivatives of dihydrosphingomyelin confirmed this structure (Shapiro et al. 1958). Long chain saturated fatty acids, mono- and even diunsaturated fatty acids (predominantly stearic, lignoceric and nervonic acids) have been isolated from sphingomyelin, but no hydroxy fatty acids (Sweeley 1963 Kishimoto et al. 1963 O Brien et al. 1964). 

The selectivity of autoxidation decreases above 60 °C since the hydroperoxides formed are subjected to homolysis giving hydroxy and alkoxy radicals (Reaction RS-4 in Fig. 3.19) which, due to their high reactivity, can abstract H-atoms even from saturated fatty acids. 

First, the discovery of malonyl CoA by Wakil and Ganguly (1959) led to the realization that not acetyl CoA, but this carboxylated derivative of acetyl CoA, was the C2 unit in fatty acid biosynthesis in animals, plants, and bacteria. Second, the studies of a number of research groups (see Wakil et al, 1964) showed that the d( — )-P-hydroxy acids and TPNH, rather than the L( + )-P-hydroxy acids and DPN utilized in fatty acid oxidation, are involved in fatty acid synthesis. Finally, the discovery and subsequent characterization of the acyl carrier protein (ACP) (Majerus et al., 1964) made it clear that this protein derivative of coenzyme A, rather than CoA, is the thioester compound to which aU of the intermediates in fatty acid synthesis in the bacteria are linked. Suggestive, but incomplete, evidence that a similar protein is involved in fatty acid biosynthesis in plants and animals has been reported (Overath and Stumpf, 1964 Alberts et al, 1964 Wakil et al, 1 ). The over-all reaction scheme for saturated fatty acid synthesis in E. coli is shovm in Fig. 2. 

Lipid A, which anchors lipopolysaccharide in the membrane, is made first. Hydroxy acids are added first to the disaccharide, followed by KDO and then saturated fatty acids. The hydroxy fatty acids come from acyl-CoA substrates whereas CMP-KDO is the source of the second addition units. After the addition of saturated fatty acids, sugars are added from nucleotide diphosphate derivatives. Various deficient mutants which lack either glucosyl- or galactosyl-transferase have been isolated. These reactions build one half of the molecule. Another lipid, phosphatidylethanolamine, has been suggested to be intimately involved in the binding of the transferase enzymes to the lipopolysaccharide acceptor. 

Chemical Composition. Wool wax is a complex mixture of esters of water-soluble alcohols (168) and higher fatty acids (169) with a small proportion (ca 0.5%) of hydrocarbons (170). A substantial effort has been made to identify the various components, but results are compHcated by the fact that different workers use wool waxes from different sources and employ different analytical techniques. Nevertheless, significant progress has been made, and it is possible to give approximate percentages of the various components. The wool-wax acids (Table 9) are predominantiy alkanoic, a-hydroxy, and CO-hydroxy acids. Each group contains normal, iso, and anteiso series of various chain length, and nearly all the acids are saturated. 

A number of amide- and ester-linked fatty acids and (/ )-3-hydroxy acids are components of the lipid A part in the LPS from Gram-negative bacteria. The acids have been tabulatedand the chemistry of lipid A summarized. The most common acids in lipid A from Enterobacteriaceae are the saturated 12 0,14 0, and 16 0, and the (/ )-3-hydroxy-14 0, The last is linked to N-2 and 0-3 of the 2-amino-2-deoxy-D-glucopyranosyl residues, and the others are ester-linked to the hydroxy acid, as in the lipid A (44) of Salmonella minnesota. Other linear and branched fatty acids, unsaturated acids, S)-2- and (/ )-3-hydroxy acids, and 3-oxotetradecanoic acid are components of lipid A from certain different species. In the lipid A from Rhizobium trifolii, 2,7-dihydroxyoctanoic acid is linked as amide to a 2-amino-2-deoxy-D-gl ucopy ranosy 1 residue. ... 

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