Metabolites from fatty acids

In contrast to the relative chemical stability of mono-epoxides, diol epoxides of fatty acids (10.52), which are formed from di-epoxides by EH, are subject to a different fate. In such metabolites, intramolecular nucleophilic substitution may occur, such that oxirane opening is accompanied by formation of a tetrahydrofuran ring [134], Such reactions of intramolecular nucleophilic substitution are discussed in detail in Sect. 11.9. In the case of diol epoxides of fatty acids, the resulting tetrahydrofuran-diols (10.53) are part of a much larger ensemble of oxygenated metabolites of fatty acids, the potential cytotoxicities of which are being evaluated [135]. 

While MS-MS allows for unequivocal identification of most metabolites, there are a few exceptions. In particular, the short-chain acylcarnitines of 4 and 5 carbons represent more than one analyte. C4-Acylcarnitine is known to be a mixture of bu-tyrylcarnitine derived from fatty acid metabolism and isobutyrylcarnitine derived from the metabolism of valine (Fig. 3.2.3) [21, 58]. C5-Acylcarnitine is a mixture of isovalerylcarnitine and 2-methylbutyrylcarnitine derived from leucine and isoleucine degradation, respectively (Fig. 3.2.4) [20, 59]. Samples of patients treated with antibiotics containing pivalic acid may contain pivaloylcarnitine another C5 species... 

As the polyketide chain is built up, any of the reductions or eliminations from fatty acid biosynthesis can occur at any stage. The simple metabolite 6-methyl salicylic acid (6-MSAJ is made in the microorganism Penicillium patulum, and it could come from the same intermediate as orsellinic acid with one reduction,... 

Volatile fungal metabolites contribute to the organoleptic properties of several other foodstuffs. Surface mould ripened cheeses such as Brie and Camembert are produced using Penicillium camembertii and, more commonly, P. caseicolum. Oct-l-en-3-ol accompanied by smaller amounts of octa-l,5-dien-3-ol and 3-one are major contributors to the aroma. These organisms also have the ability to produce 2-alkanones from fatty acids and these contribute to the odour of the cheese. 2-Methylisoborneol (7.70) and 2-methoxy-3-isopropylpyrazine (7.71) have been detected in mature cultures. An unpleasant earthy flavour encountered in some aged cultures has been attributed to the excessive produetion of 7.71. 

Plant metabolites that are capable of becoming toxic in sunlight or UVA are produced by a wide variety of biochemical pathways and thus are a structurally diverse group of natural products. Both linear and cyclic photosensitizers are known from plants. Linear phototoxins are generally derived from fatty acid precursors and typically possess conjugated double and triple bond systems. The majority of cyclic photosensitizers, on the other hand, are bi- and tricyclic aromatic molecules that may contain nitrogen, oxygen or sulfur as heterocyclic elements. 

Despite the thousands of secondary metabolites made by microorganisms, they are synthesized from only a few key precursors in pathways that comprise a relatively small number of reactions and which branch off from primary metabolism at a limited number of points. Acetyl-CoA and propionyl-CoA are the most important precursors in secondary metabolism, leading to polyketides, terpenes, steroids, and metabolites derived from fatty acids. Other secondary metabolites are derived from intermediates of the shikimic acid pathway, the tricarboxylic acid cycle, and from amino acids. The regulation of the biosynthesis of secondary metabolites is similar to that of the primary processes, involving induction, feedback regulation, and catabolite repression [6]. 

Proteins are designed to bind every conceivable molecule— from simple ions and small metabolites (sugars, fatty acids) to large complex molecules such as other proteins and nucleic acids. Indeed, the function of nearly all proteins depends on their ability to bind other molecules, or ligands, with a high... 

There are some classes of compounds present in seawater which have known biological activity but have received little attention. Compounds involved in chemical communication, especially halogenated compounds, will be discussed in other chapters. Other compounds of interest are those involved in the citric acid cycle, the major pathway of metabolism in almost all cells. Citric acid cycle intermediates and reactions are involved in the biosynthesis of most of the major metabolites, from amino acids and carbohydrates to long-chain fatty acids and porphyrins (Mahler and Cordes, 1971). The intermediates, such as succinic, fumaric, malic, oxaloacetic, citric, gly-oxylic, and oxoglutaric acids are present in almost all organisms and are certainly being produced in the sea. 

Other lipids, including triacylglycerols, phosphoacylglycerols, and steroids, are derived from fatty acids and metabolites of fatty acids, such as acetoacetyl-GoA. Free fatty acids do not occur in the cell to any great extent they are... 

Ketone body Acetoacetate or /9-hydroxybutyrate, soluble and easily transported metabolites produced from fatty acids and some amino acids. 

A major portion of the petroleum used today is derived from lipids of plants deposited in past eons. The structures of most compounds isolated from petroleum suggest a derivation from fatty acids. Various chemical changes have occurred, mostly reduction and decarboxylation, so that most petroleum is comprised of a mixture of odd- and even-chain-length hydrocarbons. Some petroleums have a variety of other compounds that appear to be derived from chemical modification of other types of secondary metabolites. 

Secondary Metabolites Derived from Fatty Acids... 

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