New natural 2-acetoxy fatty acids using chemical ionization and electron impact mass spectrometry

The Enigmatic Aliphatic Acetogenins and Their Correlations With Lipids During Seed Germination and Leaf Development of Avocado (Persea americana Mill.)

Lipids in avocados have been widely studied due to their nutritional value and several reported bioactivities. Aliphatic acetogenins are a relevant component of the avocado lipidome and have been tested for several potential food and pharma industries applications. This work followed the evolution of avocado fatty acids (FAs) and aliphatic acetogenins during seed germination and leaf growth. Oil extracts of embryonic axes, cotyledons, and leaves from seedlings and trees were divided to analyze free acetylated acetogenins (AcO-acetogenins), and free FAs. Embryonic axes from germinating seeds contained the highest amount of AcO-acetogenins and FAs; this tissue also accumulated the most diverse FA profile with up to 22 detected moieties. Leaves presented the highest variations in AcO-acetogenin profiles during development, although leaves from seedlings accumulated the simplest FA profile with only 10 different FAs. Remarkably, AcO-acetogenins represented half of the carbons allocated to lipids in grown leaves, while embryonic axes and cotyledons always contained more carbons within FAs during germination. Thus, we hypothesized the use of the AcO-acetogenin acyl chain for energy production toward β-oxidation. Also, α-linolenic and docosahexaenoic acids (DHAs) were proposed as close AcO-acetogenin intermediaries based on a correlation network generated using all these data. Another part of the oil extract was fractionated into different lipid classes before transesterification to profile FAs and acetogenins bound to lipids. Acetogenin backbones were identified for the first time in triglycerides from cotyledons and mainly in polar lipids (which include phospholipids) in all developing avocado tissues analyzed. Seed tissues accumulated preferentially polar lipids during germination, while triglycerides were consumed in cotyledons. Seedling leaves contained minute amounts of triglycerides, and polar lipids increased as they developed. Results from this work suggest acetogenins might be part of the energy and signaling metabolisms, and possibly of membrane structures, underlining the yet to establish role(s) of these unusual lipids in the avocado plant physiology.

Sulfated steroid-amino acid conjugates from the Irish marine sponge Polymastia boletiformis

Antifungal bioactivity-guided fractionation of the organic extract of the sponge Polymastia boletiformis, collected from the west coast of Ireland, led to the isolation of two new sulfated steroid-amino acid conjugates (1 and 2). Extensive 1D and 2D NMR analyses in combination with quantum mechanical calculations of the electronic circular dichroism (ECD) spectra, optical rotation, and ¹³C chemical shifts were used to establish the chemical structures of 1 and 2. Both compounds exhibited moderate antifungal activity against Cladosporium cucumerinum, while compound 2 was also active against Candida albicans. Marine natural products containing steroidal and amino acid constituents are extremely rare in nature.

Comparison of the antibacterial activity, volatiles and fatty acid composition of lipids of Phycopsis species collected at different locations from the Bay of Bengal (Orissa coast)

The fatty acid composition as well as the volatiles and an antibacterial screening of the total lipids isolated from marine sponge Phycopsis sp. collected at two different locations from the Bay of Bengal of the Orissa coast having different morphological features were studied. The content of linear saturated acids was 30.25 % in Phycopsis sp. 1, while their content reached 50.33 % in Phycopsis sp. 2. The amount of monobranched, saturated acids was 44.87 % in Phycopsis sp.1 and 38.83 % in Phycopsis sp. 2. There was more phytanic acid (7.92 %) in Phycopsis sp. 2 than in Phycopsis sp. 1 (4.06 %). The amount of 5,9-pentacosadienoic acid was found to be 5.54 % in Phycopsis sp. 1, while it was absent in Phycopsis sp. 2. Both species showed differences in their fatty acid composition and volatiles as well as in the antibacterial screening of their lipid extracts.

Two novel naturally occurring alpha-methoxy acids from the phospholipids of two Caribbean sponges

The novel (5Z)-2-methoxy-5-hexadecenoic acid (1) was identified in the phospholipids of the sponge Tethya crypta while the also novel acid (6Z)-2-methoxy-6-hexadecenoic acid (2) was found in the phospholipids of the Caribbean sponge Spheciospongia cuspidifera. The methoxy-fatty acids were mainly associated with phosphatidylethanolamine. The double bond positions were determined by gas chromatography/mass spectrometry on the corresponding dimethyl-disulfide adducts and the double bond stereochemistry was ascertained by gas chromatography/Fourier transform infrared spectroscopy. The fatty acid composition of the two sponges is reported.

Cholesterol interactions with tetracosenoic acid phospholipids in model cell membranes: role of the double-bond position

The synthesis and thermotropic properties of 1,2-di-(9Z)-9-tetracosenoylphosphatidylcholine [delta 9-PC(24:1,24:1), 1], 1,2-di-(5Z)-5-tetracosenoylphosphatidylcholine [delta 5-PC(24:1,24:1), 2], and 1,2-di-(15Z)-15- tetracosenoylphosphatidylcholine [delta 15-PC(24:1,24:1), 3] are reported. Liposomes prepared from these phospholipids differ from those of the natural sponge phospholipids, 1,2-di-(5Z,9Z)-5,9-hexacosadienoylphosphatidylcholine (4a) and the corresponding ethanolamine (4b), both of which virtually exclude cholesterol from their bilayers. The behavior of 1 and 2 is similar to that of 1,2-di-(6Z,9Z)-6,9-hexacosadienoylphosphatidylcholine (5), which exhibits a partial molecular interaction with cholesterol. In the case of 3, cholesterol appears to interact with the saturated acyl chain regions of this phospholipid in a manner similar to that of its interaction with DPPC acyl chains. This study delineates the effect of the double-bond location in long fatty acyl chains of phospholipids on their interactions with cholesterol.

Fatty acids as biological markers for bacterial symbionts in sponges

Analyses of fatty acids with carbon numbers between C12 and C22 are reported for five Great Barrier Reef sponges. These analyses indicate that phototrophic cyanobacterial symbionts (blue-green algae) present in three of the sponges are chemically distinct, whereas the other two sponges do not contain cyanobacterial symbionts. All the sponges contain other, nonphototrophic bacteria. The fatty acid analyses indicate that the non-phototrophic bacterial populations present in the different sponges are distinct in both their chemical compositions and their abundances. Nonphototrophic bacteria are estimated to account for between 60 and 350 micrograms/g (extractable fatty acids:tissue wet weight), whereas cyanobacteria account for between 10 and 910 micrograms/g. One sponge (Pseudaxinyssa sp.) contains a relatively large amount of the isoprenoid acid, 4, 8, 12-trimethyltridecanoic acid; this acid is presumed to be derived from phytol, a degradation product of chlorophyll. This sponge also contains relatively large amounts of the nonmethylene interrupted fatty acid, octadeca-5,9-dienoic acid. Analyses of interior and cyanobacteria-rich surface tissues of this sponge indicate that these two acids are probably not associated with the symbiotic cyanobacteria.

High performance liquid chromatography and fast atom bombardment mass spectrometry of unusual branched and unsaturated phospholipid molecular species

The unusual symmetrical molecular species 1,2-di-3,7,11,15-tetramethylhexadecanoyl-sn-glycero-3-phosphoglyce rol, 1,2-di-5,8,11,14-docosatetraenoyl-sn-glycero-3-phosphocholine, 1,2-di-5,9,19-octacosatrienoyl-sn-glycero-3-phosphoethanolamine, and 1,2-di-5,9,23-triacontatrienoyl-sn-glycero-3-phosphoethanolamine were isolated from the marine sponges Axinella verrucosa, Higginsia tethyoides, Tethya aurantia and Aplysina fistularis by HPLC and studied by fast atom bombardment (FAB) mass spectrometry. In addition to molecular weights, branching and double bonds were located in the fatty acyl chains of the intact phospholipid molecules, using FAB either in a positive or negative mode. Some mass spectral results were obtained on enriched phospholipid fractions rather than pure molecular species using MS/MS.

Biophysical properties of unusual phospholipids and sterols from marine invertebrates

Liposomes composed of 1,2-di-(5Z,9Z)-5-9-hexacosadienoyl-sn-glycero-3-pho sph ocholine underwent an endothermic phase transition at 42 degrees C. Cholesterol or the marine sterols studied did not affect this transition to an appreciable extent, but rather were excluded from the phospholipid bilayers. Membranes composed of 1,2-di-(5Z,9Z)-5,9-hexacosadienoyl-sn-glycero-3-pho sph ocholine displayed very similar phase properties. Effects of the marine sterols on dipalmitoylphosphatidylcholine bilayers were also investigated.

Mass spectral behavior and HPLC of some unusual molecular phospholipid species

The molecular species of the major phospholipids from the marine sponges Parasperella psila and Microciona prolifera were studied using chemical hydrolysis, enzymatic degradation and capillary gas chromatography (GC), high performance liquid chromatography (HPLC), desorption chemical ionization (DCI), fast atom bombardment (FAB) combined with collisionally activated decomposition (CAD) mass spectrometry. Two new solvent systems were developed for the isolation of these species from the sponges. Our investigations indicated the existence of unusual symmetrical phospholipids as major components. 1,2-Di-(5Z,9Z)-5,9-hexacosadienoyl-sn-glycero-3-phosph oethanolamine was found in both organisms, while 1,2-di(5Z,9Z,19Z)-5,9,19-hexacosatrienoyl-sn-gly cero-3-phosphoethanolamine was present in M. prolifera, 1,2-Di-(4Z,7Z,10Z,13Z,16Z,19Z)-4,7,1 0,13,16,19-docosahexaenoyl-sn-glycero-3- phosphocholine was the major molecular species in the PC fraction of M. prolifera.

Fast atom bombardment and tandem mass spectrometry of phosphatidylserine and phosphatidylcholine

Fast atom bombardment (FAB) desorption of phosphatidylserine and various phosphatidylcholines produces a limited number of very informative negative ions. Especially significant is the formation of (M-H)- ions for phosphatidylserine, a compound which does not yield informative high mass ions by other ionization methods. Phosphatidylcholines do not yield (M-H)- ions but instead produce three characteristic high mass ions, (M-CH+3)-, [M-HN(CH3)+3]- and [M-HN(CH3)+3-C2H2]-. Both classes of lipids also yield anions attributed to the carboxylate components of these complex lipids. FAB desorption in combination with collisional activation allows for characterization of fragmentation and determination of structural features. Collisional activation of the carboxylate anion fragments from the complex lipids is especially informative. Structural characterization of the fatty acid chain can be achieved as the released saturated carboxylate anions undergo a highly specific 1,4-elimination of H2, which results in the losses of the elements of CH4, C2H6, C3H8 . . . in a fashion entirely consistent with the chemistry of carboxylate anions desorbed from free fatty acids. These CnH2n + 2 losses begin at the alkyl terminus and progress along the entire alkyl chain. Modified fatty acids undergo a similar fragmentation; however, the modification affects the series of CnH2n + 2 losses in a manner which permits determining the type of modification and its location on the fatty acid chain.

Synthesis of 5,9-hexacosadienoic acid phospholipids. 11. Phospholipid studies of marine organisms

The synthesis of phosphatidylcholines (PC), phosphatidylethanolamines (PE) and phosphatidylserines (PS) containing two acyl chains of the naturally occurring sponge fatty acid (5Z,9Z)-5,9-hexacosadienoic acid as well as its hitherto unknown geometrical isomers is described. The PCs were prepared by deacylation of natural lecithins, followed by reacylation with fatty acid anhydrides. The synthesis of mixed-acid PCs is also reported: a diacyl product was converted to the lyso-PC by treatment with phospholipase A2 and subsequent acylation of the secondary hydroxyl group to give the desired mixed-acid PCs. The PEs and the PSs were prepared from the corresponding PCs by enzymatic transphosphatidylation catalyzed by phospholipase D. Structural assignments of the compounds were confirmed by spectroscopy (1H-NMR and MS). Ammonia chemical ionization mass spectrometry provided molecular ion and significant fragment peaks for PCs and PEs.