New advances in fatty acids as antimalarial, antimycobacterial and antifungal agents.

This review deals with the most recent findings on the antimalarial, antimycobacterial, and antifungal properties of fatty acids, with particular emphasis on novel marine fatty acids. The first section deals with the most recent and some background literature on what has been the latest developments with respect to fatty acids as antimalarial agents and the importance of enzyme inhibition, in particular the inhibition of the enoyl-ACP reductase (FabI) of Plasmodium falciparum, the principal agent responsible for malaria. This section of the review also emphasizes the latest antimalarial research with the very long-chain Delta5,9 fatty acids from sponges. The second section of the review deals with the recent literature on the antimycobacterial activity of fatty acids and the importance of enzyme inhibition, in particular the inhibition of the enoyl-ACP reductase (InhA) of Mycobacterium tuberculosis for antimycobacterial activity. The inhibitory activities of the Delta5,9 fatty acids against InhA as well as that of the alpha-methoxylated fatty acids are also discussed. The importance of Delta5,9 fatty acids as topoisomerase I inhibitors and its connection to cancer is also reviewed. The last part of the review, the antifungal section, also emphasizes the most recent research with antifungal fatty acids and the importance of enzyme inhibition, in particular N-myristoyltransferase (NMT) inhibition, for antifungal activity. This last section of the review emphasizes the latest research with the alpha-methoxylated fatty acids but the importance of acetylenic fatty acids is also considered.

New advances in the chemistry of methoxylated lipids.

Methoxylated lipids have been reviewed emphasizing the alkylglycerol ethers and fatty acids bearing the methoxy group in the alkyl chain. The literature on methoxylated lipids and their derivatives has been divided into four main groups, namely 2-methoxylated alkyl glycerols, omega-methoxylated fatty acids, mid-chain methoxylated fatty acids, and alpha-methoxylated fatty acids. The natural occurrence, biological activity, and synthesis of this interesting group of lipids are discussed. Most of these compounds have been isolated from either bacterial or marine sources, but others are mainly of synthetic origin. Among the interesting biological activities displayed by these compounds the most important are antibacterial, antifungal, antitumor, and antiviral.

Total synthesis of the novel bacterial fatty acid 16-methyl-8(Z)-heptadecenoic acid.

The recently discovered bacterial fatty acid 16-methyl-8(Z)-heptadecenoic acid was synthesized for the first time in four steps (22% overall yield) starting from commercially available 8-methylnonanoic acid. The synthetic approach provided enough material to corroborate the structure and stereochemistry of the acid, which was recently identified in a Micrococcus bacterium from Lake Pomorie in Bulgaria. Reference equivalent-chain length values in nonpolar capillary gas chromatography for methyl 16-methyl-8(Z)-heptadecenoate and methyl 16-methyl-8(E)-heptadecenoate are also reported. This information will be helpful in subsequent characterizations of these fatty acids, as well as in the total identification of the fatty acid profile of bacteria producing these compounds.

Identification and total synthesis of novel fatty acids from the Siphonarid limpet Siphonaria denticulata.

The novel fatty acids 17-methyl-6(Z)-octadecenoic acid and 17-methyl-7(Z)-octadecenoic acid were identified for the first time in nature in the mollusk Siphonaria denticulata from Queensland, Australia. The principal fatty acids in the limpet were hexadecanoic acid, octadecanoic acid, and (Z)-9-octadecenoic acid, while the most interesting series of monounsaturated fatty acids was a family of five nonadecenoic acids with double bonds at either Delta(7), Delta(9), Delta(11), Delta(12), or Delta(13). The novel compounds were characterized using a combination of GC-MS and chemical transformations, such as dimethyl disulfide derivatization. The first total syntheses for the two novel methyl-branched nonadecenoic acids are also described, and these were accomplished in four to five steps and in high yields.

Characterization of novel methyl-branched chain fatty acids from a halophilic Bacillus species.

The 4-methylated fatty acids 4,9-dimethyldecanoic, 4,11-dimethyldodecanoic, 4,10-dimethyldodecanoic, and 4,13-dimethyltetradecanoic acid as well as the 2-methylated fatty acids 2,13-dimethyltetradecanoic and 2,12-dimethyltetradecanoic acid were identified for the first time in nature in the halophilic bacterium Bacillus sp. isolated from the salt pans of Burgas in Bulgaria. The principal fatty acids in this bacterium were a series of iso-anteiso fatty acids with chain lengths between C11 and C19, but an interesting series of linear alkylbenzene fatty acids with chain lengths between C10 and C14, such as 12-phenyldodecanoic acid, were also identified. The novel 4-methylated fatty acids were characterized using a combination of GC-MS and chemical transformations such as N-acylpyrrolidide derivatization. The 2-methylated fatty acids were also identified by GC-MS and gas chromatographic coelution with synthetic samples. The novel methyl-branched fatty acids probably originated from the selective incorporation of methylmalonyl-CoA by one of the fatty acid-synthesizing enzymes of the bacterium.

New methoxylated fatty acids from the Caribbean sponge Callyspongia fallax.

The saturated 2-methoxylated fatty acids 2-methoxytetradecanoic acid (1), 2-methoxypentadecanoic acid (2), and 2-methoxyoctadecanoic acid (3) as well as the Delta6 monoenoic methoxylated fatty acids (6Z)-2-methoxy-6-tetradecenoic acid (4), (6Z)-2-methoxy-6-pentadecenoic acid (5), and (6Z)-2-methoxy-13-methyl-6-tetradecenoic acid (7) were identified for the first time in nature in the phospholipids from the Caribbean sponge Callyspongia fallax. These findings expand the occurrence of 2-methoxylated fatty acids to C14-C15 chain lengths and establish new fatty acid biosynthetic possibilities for marine organisms. The novel methoxylated fatty acids could have originated from the phospholipids of a bacterium in symbiosis with the sponge.

The first naturally occurring alpha-methoxylated branched-chain fatty acids from the phospholipids of Amphimedon complanata.

The phospholipid fatty acid composition of the sponge Amphimedon complanata was reinvestigated, and the 2-methoxy-13-methyltetradecanoic acid, 2-methoxy-14-methylpentadecanoic acid, and 2-methoxy-13-methylpentadecanoic acid were identified for the first time in nature. Structure characterization was accomplished by means of gas chromatographic retention times and gas chromatography-mass spectrometry. These acids could have originated from bacteria in symbiosis with the sponge.

Two novel iso-branched octadecenoic acids from a Micrococcus species.

The novel fatty acids 16-methyl-6(Z)-heptadecenoic acid and 16-methyl-8(Z)-heptadecenoic acid were identified for the first time in nature in a species of the bacterium Micrococcus isolated from Lake Pomorie in Bulgaria. The principal fatty acids in this bacterium were a series of iso-anteiso fatty acids with chain lengths between C(14) and C(24), while the most interesting series of monounsaturated fatty acids was a family of Delta(6) fatty acids with chain lengths between C(14) and C(17). The novel compounds were characterized using a combination of GC-MS and chemical transformations, such as dimethyl disulfide derivatization and catalytic hydrogenation. The results established for the first time a bacterial origin for some of these Delta(6) fatty acids.

Identification and total synthesis of a novel dimethylated fatty acid from the Caribbean sponge Calyx podatypa.

The dimethylated fatty acid 9,13-dimethyltetradecanoic acid was identified for the first time in nature in the Caribbean sponge Calyx podatypa where it occurs together with the rare 10, 13-dimethyltetradecanoic acid. The characterization of the novel compound was accomplished using GC-MS, pyrrolidide derivatization, and a five-step total synthesis starting with 8-bromooctanoic acid. The first racemic total synthesis for the rare 10, 13-dimethyltetradecanoic acid is also described.

Unusual lipid composition of a Bacillus sp. isolated from Lake Pomorie in Bulgaria.

The lipid composition of a Bacillus sp., isolated from Lake Pomorie in Bulgaria, was unusual and consisted of 26 different fatty acids between C12 and C26, with anteiso C15-C17 saturated fatty acids predominating. The furan fatty acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid, was also identified, a new finding for this genus. The hydrocarbons consisted of 30 different monounsaturated hydrocarbons, between C25 and C30, with the iso-iso, iso-anteiso, anteiso-anteiso, iso-normal, and anteiso-normal methyl branching for odd-numbered chains, and the iso-iso, iso-anteiso, iso-normal, and anteiso-normal methyl branching for even-numbered chains. The double bond positions in these hydrocarbons were determined by dimethyl disulfide derivatization followed by GC-MS, and the double-bond cis configuration was confirmed by infrared spectroscopy. Some previously unknown hydrocarbons in bacteria, such as (Z)-3,21-dimethyl-9-tricosene, (Z)-3,21-dimethyl-10-tricosene, (Z)-2,24-dimethyl-11-pentacosene, and (Z)-2,25-dimethyl-13-hexacosene were identified. Sterols were detected and were based on the sitosterol nucleus.

Synthesis of racemic 9-methyl-10-hexadecenoic acid.

The marine bacterial fatty acid 9-methyl-10-hexadecenoic acid was conveniently prepared in 6 steps and in a 22% overall yield, starting from commercially available methyl 10-hydroxydecanoate. The naturally occurring fatty acid has the E double bond configuration as confirmed by gas chromatographic co-elution experiments.

Facile syntheses for (5Z,9Z)-5,9-hexadecadienoic acid, (5Z,9Z)-5,9-nonadecadienoic acid, and (5Z,9Z)-5,9-eicosadienoic acid through a common synthetic route.

The delta 5,9 fatty acids (5Z,9Z)-5,9-hexadecadienoic acid, (5Z,9Z)-5,9-nonadecadienoic acid, and (5Z,9Z)-5,9-eicosadienoic acid were synthesized for the first time in four steps (9-12% overall yield) starting from commercially available 2-(2-bromoethyl)-1,3-dioxolane. The synthetic approach provided enough material to corroborate the structure and stereochemistry of (5Z,9Z)-5,9-nonadecadienoic acid which was recently identified in the flowers of Malvaviscus arboreus (Malvaceae). The novel phospholipids 1-hexadecanoyl-2-[(5Z,9Z)-5,9-eicosadienoyl]-sn-glycer o-3-phosphocholine and 1-octadecanoyl-2-[(5Z,9Z)-5,9-eicosadienoyl]-sn- glycero-3-phosphocholine were also synthesized from commercially available L-alpha-phosphatidylcholine (egg yolk) and characterized by positive ion electrospray mass spectrometry. These are the first examples of unsymmetrical phospholipids with saturated fatty acids at the sn-1 position and delta 5,9 fatty acids at the sn-2 position.

Facile total synthesis and antimicrobial activity of the marine fatty acids (Z)-2-methoxy-5-hexadecenoic acid and (Z)-2-methoxy-6-hexadecenoic acid.

The total synthesis of the naturally occurring (Z)-2-methoxy-5-hexadecenoic acid and (Z)-2-methoxy-6-hexadecenoic acid was accomplished using as a key step Mukaiyama's trimethylsilyl cyanide addition to 4- and 5-pentadecenal, respectively. These syntheses further confirm the structures of the natural marine fatty acids and corroborate their cis double-bond stereochemistry. The title compounds were antimicrobial against the Gram-positive bacteria Staphylococcus aureus (MIC 0.35 micromol/mL) and Streptococcus faecalis (MIC 0.35 micromol/mL).

Identification and total synthesis of novel fatty acids from the Caribbean sponge Calyx podatypa.

The phospholipid fatty acid composition of the Caribbean sponge Calyx podatypa was studied, and 85 different fatty acids were identified, in particular the 11-methylpentadecanoic acid and 10-tricosenoic acid, which have no literature precedence. Structural characterization was accomplished by means of gas chromatography-mass spectrometry on their corresponding methyl esters and dimethyl disulfide derivatives. The structure of 11-methylpentadecanoic acid was further confirmed by total synthesis (17% overall yield) starting from commercially available 10-hydroxydecanoic acid.

Fatty acid composition of bacteria associated with the toxic dinoflagellate Ostreopsis lenticularis and with Caribbean Palythoa species.

The fatty acid composition of a Pseudomonas sp. (Alteromonas) and its host, the dinoflagellate Ostreopsis lenticularis, vectors in ciguatera fish poisoning, has been studied. The major fatty acids in O. lenticularis were 16:0, 20:5n-3, and 22:6n-3, but 18:2n-6, 18:3n-3, and 18:n-3 were also identified. In contrast to other dinoflagellates, 1 8:5n-3 was not detected in O. lenticularis. Even-chain fatty acids such as 9-16:1, 11-18:1, and 13-20:1 predominated in the Pseudomonas sp. from O. lenticularis, but 1 6-20% of (E)-11-methyl-12-octadecenoic acid was also identified. The chirality of the latter was confirmed by total synthesis (28% overall yield) starting from oxacyclotridecan-2-one. The fatty acid compositions of two other Pseudomonas species, from the palytoxin-producing zoanthids Palythoa mamillosa and P. caribdea, were also studied and were similar to that of the Pseudomonas sp. from O. lenticularis. The possibility of using some of these fatty acids as chemotaxonomic lipids in identifying marine animals that consume toxic dinoflagellates or zoanthids is discussed.

Neighboring methoxyl participation in the acid catalyzed methoxylation of methylene-interrupted fatty acids.

The boron trifluoride-methanol derivatization of methyl 9,12-octadecadienoate was studied. This methylene-interrupted diene was reacted with 50% BF3-MeOH for 15 h at 0-5 degrees C and the four monomethoxy and two dimethoxy derivatives thus obtained were analyzed by gas chromatography-mass spectrometry. The only dimethoxy adducts observed were characterized as methyl 9,12-dimethoxyoctadecanoate and methyl 10,13-dimethoxyoctadecanoate. The complete regiospecificity observed in the formation of the dimethoxy adducts is best explained by a common O-methyltetrahydrofuranium ion as the only intermediate under these reaction conditions.

Identification of the novel antimicrobial fatty acid (5Z,9Z)-14-methyl-5,9-pentadecadienoic acid in Eunicea succinea.

The phospholipid fatty acid composition of Eunicea succinea was investigated, and the novel (5Z,9Z)-14-methyl-5,9-pentadecadienoic acid was identified. Structural characterization was accomplished by means of mass spectrometry of its pyrrolidide derivative, NMR, FT1R, and total synthesis. Other interesting phospholipid fatty acids in E. succinea were the tetracosapolyenoic acids 6,9,12,15,18,21-tetracosahexaenoic acid (24:6) and 6,9,12,15,18-tetracosapentaenoic acids (24:5). The title compound was particularly active against Gram-positive bacteria such as Staphylococcus aureus (MIC 0.24 mumol/mL) and Streptococcus faecalis (MIC 0.16 mumol/ mL).

Unusual fatty acid compositions of the hyperthermophilic archaeon Pyrococcus furiosus and the bacterium Thermotoga maritima.

The fatty acid compositions of the hyperthermophilic microorganisms Thermotoga maritima and Pyrococcus furiosus were studied and compared. A total of 37 different fatty acids were identified in T. maritima, including the novel 13,14-dimethyloctacosanedioic acid. In contrast, a total of 18 different fatty acids were characterized, as minor components, in P. furiosus, and these included saturated, monounsaturated, and dicarboxylic acids. This is the first report of fatty acids from an archaeon.

The fatty acid composition of a Vibrio alginolyticus associated with the alga Cladophora coelothrix. Identification of the novel 9-methyl-10-hexadecenoic acid.

The fatty acid composition of a new strain of Vibrio alginolyticus, found in the alga Cladophora coelothrix, was studied. Among 38 different fatty acids, a new fatty acid, 9-methyl-10-hexadecenoic acid and the unusual 11-methyl-12-octadecenoic acid, were identified. Linear alkylbenzene fatty acids, such as 10-phenyldecanoic acid, 12-phenyldodecanoic acid and 14-phenyltetradecanoic acid, were also found in V. alginolyticus. The alga contained 43% saturated fatty acids, and 28% C16-C20 polyunsaturated fatty acids of the n-3 and n-6 families.

Dimethyl disulfide derivatization of ethyl (9Z,12Z)-9, 12-octadecadienoate and ethyl (9E,12E)-9,12-octadecadienoate.

The dimethyl disulfide derivatization of ethyl (9Z,12Z)-9,12-octadecadienoate and ethyl (9E,12E)-9,12-octadecadienoate was studied. These methylene-interrupted dienes were reacted with dimethyl disulfide and I2 for 72 h at 50 degrees C and the tetrahydrothiopyran, thietane, and tetrahydrothiophene derivatives thus obtained were analyzed by gas chromatography-mass spectrometry. Each configurational isomer displayed a unique gas chromatography trace for the 4-, 5- and 6-membered ring cyclization products thus obtained. Therefore, the cis-cis and trans-trans double bond stereochemistry of 9,12-octadecadienoates can now be determined by dimethyl disulfide derivatization.