Ω-cyclohexyl Fatty Acids Research Articles

An Overview on Cyclic Fatty Acids as Biomarkers of Quality and Authenticity in the Meat Sector.

A survey was conducted to determine the content of cyclopropane fatty acids (CPFAs) and ω-cyclohexyl fatty acids (CHFAs) by using gas chromatography- mass spectrometry (GC-MS) and proton nuclear magnetic resonance (1H NMR) techniques in various meat samples from different species, including commercial samples and complex and thermally processed products (i.e., Bolognese sauce). The CPFAs concentration (as the sum of two isomers, namely dihydrosterculic acid and lactobacillic acid) in bovine meat fat (ranging between 70 and 465 mg/kg fat) was positively related to a silage-based diet, and therefore, they are potential biomarkers for monitoring the feeding system of cattle. CHFAs, such as 11-cyclohexylundecanoic and 13-cyclohexyltridecanoic acids, were only found in lipid profiles from ruminant species, and a linear trend was observed in their content, together with iso-branched fatty acids (iso-BCFAs) deriving from ruminal fermentation, as a function of bovine meat percentage in both raw and cooked minced meat. Thus, CHFAs are potential biomarkers for the assurance of the meat species and, combined with iso-BCFAs, of the beef/pork ratio even in complex meat matrices. The proposed approaches are valuable novel tools for meat authentication, which is pivotal in the management of meat quality, safety, and traceability.

Cyclopropyl and ω-cyclohexyl fatty acids as quality markers of cow milk and cheese

Content of cyclopropyl and ω-cyclohexyl fatty acids of microbial origin, respectively, from silage and rumen, was determined by GC–MS and confirmed by 1H NMR in more than 200 milk samples from dairy cows fed with different forages. Cyclopropyl fatty acids (about 0.1% of milk fat) were detected for the first time in milk and they were present only in milk samples from cows fed with forages containing maize silage, which is not allowed to produce milk for some PDO cheeses as Parmigiano-Reggiano. Their determination can be proposed as a quality parameter of milk or feed and it can be useful especially to distinguish cheeses sold as Parmigiano Reggiano from others cheeses. The content of ω-cyclohexyl tridecanoic acid varied from 0.0% to 0.15% of milk fat, and it was higher in milk samples from cows fed with diets richer in cereal meals.

Atomic force microscopic investigations of the gel phase of phosphatidylcholines containing ω-cyclohexyl fatty acids

The gel phase of 1,2-di-13-cyclohexyltridecanoyl-sn-glycero-3-phosphocholine (13cyPC) and 1,2-di-14-cyclohexyltetradecanoyl-sn-glycero-3-phosphocholine (14cyPC) was investigated by atomic force microscopy. 13cyPC forms a gel phase with a very high degree of chain order resembling the subgel phase of PCs with saturated linear chains. For 13cyPC, flat surfaces, ripple structures, and singular ripple lines at domain borders were observed. Ripples developed only in multilamellar stacks (5 or more lamellae) on the top surface of the stack. The ripple periodicity was 33 nm and the ripple amplitude only 0.3 nm. 14cyPC shows a gel phase with much higher degree of disorder. For 14cyPC, ripples were observed on all layers, the ripples having much larger amplitudes (3 nm) but a similar periodicity of 37 nm. In addition, irregular bilayer deformations appearing almost like honeycomb structures were observed. The apparent periodicity of the holes in this structure was 30 nm and thus similar to the ripple period. The hole depth was 2 nm or larger. These deformations were only very pronounced for every second layer. For 14cyPC, the higher disorder in the gel phase seen by spectroscopic techniques enables larger amplitudes for the deformation of the lamellae. These deformations may be related to the convex–concave bilayer deformations seen by freeze fracture electron microscopy in other systems (H. W. Meyer, K. Semmler, W. Rettig, W. Pohle, A. S. Ulrich, S. Grage, C. Selle and P. J. Quinn, Chem. Phys. Lipids, 2000, 105, 149).

Biosynthesis of ω-cyclohexyl fatty acids in Alicyclobacillus acidocaldarius: the stereochemistry of the initial 1,4-conjugate elimination

S. Handa and H. G. Floss, Chem. Commun., 1997, 153 DOI: 10.1039/A607122H

Biosynthesis of the cyclohexanecarboxylic acid starter unit of .omega.-cyclohexyl fatty acids in Alicyclobacillus acidocaldarius

The formation of the cyclohexanecarboxylic acid starter unit of ω-cyclohexyl fatty acids from shikimic acid in Alicyclobacillus acidocaldarius (formerly Bacillus acidocaldarius) has been studied. Feeding experiments with 13 C- and 2 H-labeled samples of shikimic acid and potential intermediates in the wild type and two blocked mutants demonstrated that the formation of cyclohexanecarboxylic acid in this organism follows the same pathway as in Streptomyces collinus (J. Am. Chem. Soc., preceding paper in this issue). (1S,3S)-3-Hydroxycyclohexanecarboxylic acid (20) is accumulated by blocked mutant 2, indicating that 5-hydroxycyclohex-1-enecarboxylic acid (6) is first reduced to the hydroxy acid 20 and then dehydrated to 2-cyclohexenecarboxylic acid (8)

Properties of Bacillus acidocaldarius mutants deficient in ?-cyclohexyl fatty acid biosynthesis

Mutants of the thermoacidophilic Bacillus acidocaldarius, auxotrophic for shikimate or cyclohyxyl-carboxylate, were isolated and characterized. The cyclohexylcarboxylate auxotrophs could be divided by crossfeeding experiments into two groups according to their genetic block. The cyclohexylcarboxylate auxotrophs were deficient in ω-cyclohexyl fatty acid biosynthesis. If the mutants were fed with branched-chain amino acids or short branched-chain fatty acids instead of cyclohexylcarboxylate they form a fatty acid pattern consisting of branched-chain fatty acids. In the high temperature/low pH range the growth yield of cells with this fatty acid pattern is lower as compared to wild type cells or mutants fed with cyclohexylcarboxylate. The same cells are also more sensitive to heat shocks and ethanol. The transport systems for lysine, glutamate and glucose are severely altered by the fatty acid pattern. It was also shown that the density of the lipids containing ω-cyclohexyl fatty acids is higher compared to cells with branched-chain fatty acids. Thus it could be supposed that this alteration influences transport systmes in a direct manner or via energization of the cytoplasmic membrane.

An infrared spectroscopic study of the thermotropic phase behavior of phosphatidylcholines containing ω-cyclohexyl fatty acyl chains

The thermotropic phase behavior of an odd- and an even-numbered member of the homologous series of 1,2-di-ω-cyclohexylphosphatidylcholines was studied using Fourier transform infrared spectroscopy. The results obtained indicate that the pronounced discontinuities in the behavior of the odd- and even-numbered homologoues observed by differential scanning calorimetry can be attributed to differences in the organization of their respective gel states. The single phase transition exhibited by the odd-numbered compounds upon heating is shown by infrared spectroscopy to be a direct transition from α condensed, subgel-like phase (L c phase) to the liquid-crystalline state (L α phase). In contrast, the multiple transitions exhibited by the even-numbered homologues are shown to be due to the initial conversion of an L β-like phase to a more loosely packed gel phase, followed by the acyl chain-melting transition. Moreover, the major changes in the interaction between the acyl chains, and in the organization of the interfacial region of the bilayers formed by the even-numbered homologous, occur at temperatures below that of the chain onset-melting phase transition. The infrared spectroscopic changes observed also suggest that above the chain-melting transition, the odd- and even-numbered homologues form similar liquid-crystalline phases that are more ‘ordered’ than those of normal saturated straight-chain phosphatidylcholines. Most likely this is because the large size and the intrinsic rigidity of the ω-cyclohexyl group reduces the conformational disorder of the liquid-crystalline state by ‘damping’ all acyl chain motions. The formation of a relatively ordered liquid-crystalline state may be the critical property exploited by the thermoacidophylic organisms in which ω-cyclohexyl fatty acids naturally occur.

Zinc uptake of Curtobacterium possessing ω-cyclohexyl fatty acids and zinc-binding activity of its membrane

Zinc uptake of Curtobacterium possessing ω-cyclohexyl fatty acids and zinc-binding activity of its membrane

Zinc uptake of Curtobacterium possessing ω-cyclohexyl fatty acids and zinc-binding activity of its membrane

The immobilization of zinc taken up by Curtobacterium pusillum strain Z-96 possessing ω-cyclohexyl fatty acids and the zinc-binding activity of the membrane were investigated. The zinc taken up was immobilized in the membrane fraction to a great extent; little zinc was found in the cytoplasmic fraction. Zinc-binding activity of membranes was comparable to the amount of zinc immobilized by the intact cells. The level of ω-cyclohexyl fatty acids and the zinc-binding activity of the membrane were increased by the addition of zinc to the culture medium. The amount of bound zinc was approximately proportional to the level of ω-cyclohexyl fatty acids. In addition, the zinc-binding activity was not appreciably influenced by acidic or high-temperature treatment of membranes.

DSC-studies of phospholipids containing iso-branched and ω-cyclohexane fatty acids

Differential Scanning Calorimetry (DSC) and Differential Scanning Densitometry (DSD) was employed to study the phase behavior of phospholipids with iso-branched and ω-cyclohexyl fatty acids. Phosphatidylcholines (PC) and phosphatidylethanolamines (PE) with iso-branched fatty acids show complicated phase behavior with several gel-gel transitions with odd-even effects. These odd-even effects are even more pronounced for phosphatidylcholines with ω-cyclohexyl fatty acids (cyPCs). Odd-numbered cyPCs show a large main transition with strong hysteresis while the even-numbered cyPCs have several transitions but show no hysteresis. These differences in thermotropic behavior are also reflected in their molecular volumes. The odd-numbered cyPCs display much tighter packing in the gel phase than the even-numbered analogues. Binary mixtures of cyPCs with either straight chain PCs or iso-branched PCs show eutectic behavior. This is also observed when cyPCs of different chain length are mixed.

Occurrence of Curtobacterium sp. possessing ?-cyclohexyl fatty acids in soil with zinc added

A bacterial strain, Curtobacterium sp., isolated from a soil with zinc added possessed ω-cyclohexyl fatty acids. ω-Cyclohexyl undecanoic acid made up 47% of the total fatty acids; it was the most abundant fatty acid in the strain grown in tryptone medium. 12-Methyl tetradecanoic acid (23%) and 14-methyl hexadecanoic acid (22%) were also major fatty acids. The proportion of ω-cyclohexyl undecanoic acid increased as the pH of the medium decreased and as the culture temperature increased.

Taxonomic Significance of Cellular Fatty Acid Composition in Some Coryneform Bacteria

A total of 76 strains of coryneform bacteria belonging to the genera Arthrobacter, Brevibacterium, Caseobacter, Cellulomonas, Corynebacterium, and Curtobacterium were divided into four groups on the basis of their cellular fatty acid compositions. Cells with saturated and monounsaturated straight-chain fatty acids were designated type I. Strains in this group had meso-diaminopimelic acid and arabinogalactan in their cell walls. In some strains, 10-methyl fatty acids were found. Type I was divided into six subtypes based on fatty acid composition. Type II cells contained iso-anteiso acids and were found in 43 strains of Arthrobacter, Brevibacterium, Cellulomonas, Curtobacterium, and coryneform bacteria with diaminobutyric acid-peptidoglycan. Small differences in fatty acid composition were found among the strains of this type, and the fatty acid compositions of type II strains varied remarkably depending on the media used. Type III strains were characterized by the presence of ω-cyclohexyl fatty acids. In two strains of Curtobacterium pusillum, approximately 60% of the cellular fatty acid was ω-cyclohexyl undecanoic acid. Type IV strains had highly complex patterns of iso, anteiso, normal, saturated, unsaturated, 10-methyl, and 2-hydroxy fatty acids. Five strains of Arthrobacter simplex, Arthrobacter tumescens, and “Brevibacterium lipolyticum” possessed this type of fatty acid composition.

Occurrence of .OMEGA.-cyclohexyl fatty acids in Curtobacterium pusillum strains.

ω-Cyclohexyl fatty acids were found in two strains of Curtobacterium pusillum. ω-Cyclohexyl undecanoic acid constituted 26 to 96% of the total fatty acids in the bacteria. Trace amounts of ω-cyclohexyl tridecanoic acid were also observed. The fatty acids other than the cyclohexyl acids found were 12-methyl tetradecanoic acid, 14-methyl hexadecanoic acid, and trace amounts of several straight chain and methyl-branched fatty acids. The proportion of the ω-cyclohexyl acids increased both with increasing growth temperature and with the increase in the concentration of glucose in the culture medium.

Metabolism of naphthenic hydrocarbons. Utilization of a monocyclic paraffin, dodecylcyclohexane, by rat

3H-Dodecylcyclohexane was incorporated in rat diet in order to study the metabolic utilization by mammals of a monocycloparaffin chosen as a typical naphthenic constituent of mineral oils. Dodecylcyclohexane was largely absorbed. No elimination of the hydrocarbon was observed in urine while an extended excretion of 3H occurred via this route. About 7% of absorbed dodecylcyclohexane was stored in the carcass, while the rest was omega-oxidized to cyclohexyldodecanoic acid, which incorporated into neutral lipids and phospholipids. The aliphatic chain of this unusual fatty acid underwent the normal fatty acid degradation pathways, leading to even fatty acids, squalene, cholesterol and nonlipid resynthesis, while the cyclohexyl ring was eliminated as urinary metabolites. Incorporation of omega-cyclohexyl fatty acids in phospholipids may raise a point of toxicological significance which is to be investigated.