Branchedchain Fatty Acids

Whilst straight-chain fatty acids are the most common, branched-chain acids have been found to occur in mammalian systems, e.g. in wool fat and butter fat. They are also characteristic fatty acid constituents of the lipid part of cell walls in some

oenanthotoxin falcarinol (panaxynol) OH

panaxytriol

wyerone

Figure 3.10

pathogenic bacteria. Several mechanisms appear to operate in their formation. Thus, the structure of corynomycolic acid from Corynebacterium diph-theriae can be rationalized from a combination of two palmitic acid units (Figure 3.12). Methyl side-chains can be introduced by using methylmalonyl-CoA instead of malonyl-CoA as the chain extending agent (Figure 3.13). Methylmalonyl-CoA arises by biotin-dependent carboxylation of propionyl-CoA in exactly the same way as malonyl-CoA was formed (see page 17). 2,4,6,8-Tetramethyldecanoic acid found in the preen gland wax of the goose (Anser anser) is produced from an acetyl-CoA starter, and four methylmalonyl-CoA chain extender units. The incorporation of propionate as well as acetate is also a feature of many microbial antibiotic structures (see page 17). However, in other examples, methyl side-chains can be produced by a C-alkylation mechanism using S-adenosylmethionine (SAM). Tuberculostearic acid (Figure 3.14) found in Mycobacterium tuberculosis, the bacterium causing tuberculosis, is derived from oleic acid by alkylation on C-10, cicutoxin

Echinacea

Echinacea consists of the dried roots of Echinacea purpurea, E. angustifolia, or E. pallida (Compositae/Asteraceae), herbaceous perennial plants indigenous to North America, and widely cultivated for their large daisy-like flowers, which are usually purple or pink. Herbal preparations containing the dried root, or extracts derived from it, are promoted as immunostimulants, particularly as prophylactics and treatments for bacterial and viral infections, e.g. the common cold. Tests have validated stimulation of the immune response, though the origins of this activity cannot be ascribed to any specific substance. Activity has variously been assigned to lipophilic alkylamides, polar caffeic acid derivatives, high molecular weight polysaccharide material, or to a combination of these. Compounds in each group have been demonstrated to possess some pertinent activity, e.g. immunostimulatory, anti-inflammatory, antibacterial or antiviral effects. The alkylamides comprise a complex mixture of unsaturated fatty acids as amides with 2-methylpropanamine (isobutylamine) or 2-methylbutanamine, amines which are probably decarboxylation products from valine and isoleucine respectively. The acid portions are predominantly Cn and Ci2 diene-diynes or tetraenes (Figure 3.11). These compounds are found throughout the plant though relative proportions of individual components vary considerably. The root of E. purpurea contains at least 12 alkylamides (about 0.6%), of which C12 diene-diynes predominate; levels of these compounds fall significantly during drying and storage. Caffeic acid derivatives present include caffeic acid (see page 132), chlorogenic acid (5-O-caffeoylquinic acid, see page 132), 2-0-caffeoyltartaric acid, and cichoric acid (2,3-di-O-caffeoyltartaric acid) (Figure 3.11). Cichoric acid is a major component (0.6-2.1%) in E. purpurea, but only minor in the other species.

_(Continues)

Dihydrosterculic Acid
diene-diyne alkylamides

tetraene alkylamides O CO2H

tetraene alkylamides O CO2H

HO2C O cichoric acid

HO2C O cichoric acid

Figure 3.11

SCoA

corynomycolic acid

CO2H

propionyl-CoA

CO2, ATP SCoA biotin

Figure 3.12

CO2H

corynomycolic acid

SCoA

methylmalonyl-CoA SCoA

"mrr

CO2H

2,4,6,8-tetramethyldecanoic acid

Figure 3.13

initiated by the double bond electrons. A postulated carbocation intermediate could then be discharged by accepting hydride from NADPH giving tuber-culostearic acid. Alternatively, loss of a proton via cyclopropane ring formation could occur giving dihydrosterculic acid. This is known to be dehydrogenated to sterculic acid, an unusual fatty acid containing a highly strained cyclopropene ring. Sterculic acid is present in the seed oil from Sterculia foetida (Sterculiaceae) and with similar cyclopropene acids, e.g. malvalic acid, is present in edible cottonseed oil from Gossypium species

(Malvaceae). Malvalic acid is produced from ster-culic acid by chain shortening from the carboxyl end (Figure 3.14). Sterculic acid is an inhibitor of the A9-desaturase which converts stearic acid into oleic acid and is potentially harmful to humans in that it can alter membrane permeability and inhibit reproduction.

Chaulmoogric and hydnocarpic acids (Figure 3.15) are cyclopentenyl fatty acids found in chaul-moogra oil expressed from seeds of Hydnocar-pus wightiana (Flacourtiaceae). These acids are known to arise by malonate chain extension of the

Ad h3c-s© sam oleoyl-CoA

oleoyl-CoA

electrophilic addition: O SAM as alkylating agent

SCoA

SCoA

carbocation intermediate \ NADPH

cation discharged by addition of hydride .

from NADPH |

carbocation intermediate \ NADPH

cation discharged by addition of hydride .

from NADPH |

cation discharged by formation of cyclopropane ring and loss of proton

SCoA

dihydrosterculic acid desaturation

,CO2H

tuberculostearic acid

CO2H

sterculic acid a-oxidation

,CO2H

Figure 3.14

malvalic acid

CO2H

2-cyclopentenyl-carboxyl-CoA

,CO2H

hydnocarpic acid

,CO2H

chaulmoogric acid

Figure 3.15

coenzyme A ester of 2-cyclopentenyl carboxylic acid as an alternative starter unit to acetate, demonstrating a further approach to unusual fatty acids. Chaulmoogra oil provided for many years the only treatment for the relief of leprosy, these two acids being strongly bactericidal towards the leprosy infective agent Mycobacterium leprae. Purified salts and esters of hydnocarpic and chaulmoogric acids were subsequently employed, until they were then themselves replaced by more effective synthetic agents.

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Cure Tennis Elbow Without Surgery

Everything you wanted to know about. How To Cure Tennis Elbow. Are you an athlete who suffers from tennis elbow? Contrary to popular opinion, most people who suffer from tennis elbow do not even play tennis. They get this condition, which is a torn tendon in the elbow, from the strain of using the same motions with the arm, repeatedly. If you have tennis elbow, you understand how the pain can disrupt your day.

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