Identification of molecular species of monoalkyldiacylglycerol from the squid Berryteuthis magister using liquid chromatography-APCI high-resolution mass spectrometry.

Monoalkyldiacylglycerol (MADAG) is an important lipid class in mollusks, corals, starfishes, and some species of zooplankton. Up to 80% of liver oils of squids and sharks are comprised of MADAG. Except for one fish species, there are no data on the composition of MADAG molecular species of marine organisms. The molecular species of MADAG obtained from digestive glands of the deep-sea squid Berryteuthis magister were identified. High-performance liquid chromatography (HPLC) and tandem high-resolution mass spectrometry (HRMS) with atmospheric pressure chemical ionization (APCI) were applied. The mass spectra of each molecular species contained positive quasi-molecular ion [M+H]+ with fragment ions [M-R'CO2]+, [M-R''CO2]+, and [M-OR''']+, as well as negative cluster ion [M+2H2OH]- without fragments. The exact masses of the negative ions allowed determination of the molecular formulas and the number of double bonds; the positive fragment ions were used to determine the location of acyl and alkyl groups in MADAG molecules. Ninety molecular species of MADAG were revealed. The regiospecific composition was identified for 72 individual molecular species. Eleven pairs of positional isomers of acyl groups were found. Four molecular ions were produced by a mixture of acyl/alkyl isomers. Most of molecular species contained 16:0e or 18:1e alkyl groups in the sn-1 position, whereas polyunsaturated fatty acids mainly esterified the sn-2 position of MADAG from B. magister. These structural features are supposed to be characteristic for biologically active MADAG.

Application of fatty acids for chemotaxonomy of reef-building corals.

Sixteen scleractinian species of six coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Pectiniidae, and Fungiidae) from Vietnam were analyzed for fatty acid (FA) composition. Except for the Poritidae species, total lipids of the corals had the same set of FAs, about 50% of them being unsaturated acids. Some coral families had high levels of characteristic FAs: 20:3(n-6), 20:4(n-3), and 22:6(n-3) in Pocilloporidae; 18:1(n-9) and 22:6(n-3) in Poritidae; and 18:3(n-6) and 22:5(n-3) in Faviidae. For the first time in hexacorals, unsaturated C(24) FAs (24:1(n-9), 24:2(n-6), 24:2(5,9), 24:3(5,9,17), and 24:4(n-3)) were discovered in the Poritidae species. The highest level of 18:1(n-7), odd-chain and branched FAs (7.5% in total) was detected in Sandalolitha robusta. The data obtained on the contents of ten principal C(18)-C(22) polyunsaturated FAs (PUFAs) for the 16 specimens were combined with data on the 19 reef-building coral specimens investigated previously and subjected to multidimensional scale analysis (MSA). The representative coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Dendrophylliidae, and Milleporidae) were separated by MSA according to the composition of their principal PUFAs. Therefore, PUFAs may serve as chemotaxonomic markers for reef-building corals at the family level. Family-specific compositions of coral zooxanthellae characterized by different PUFA profiles, which affect the PUFA content of whole coral colonies, were supposed to be the probable cause of the discovered chemotaxonomic distinctions between reef-building corals.

Lipid class and fatty acid composition of the boreal soft coral Gersemia rubiformis.

Total lipid, phospholipid, and FA composition and distribution of FA between polar lipids (PL) and neutral lipids (NL) were investigated in the boreal soft coral Gersemia rubiformis from the Bering Sea. The total lipids were mostly hydrocarbons and waxes (33.7%) and PL (33.1%). The content of monoalkyldiacylglycerols (9.7%) exceeded the content of TAG (6.7%). PC and PE constituted 31.4% and 25.6% of total phospholipids, respectively. Principal FA were 16:0, 16:1n-7, 18:0, 18:1n-9, 18:1n-7, 20:1n-7, 20:4n-6, 20:4n-3, 20:5n-3, 22:5n-3, 22:6n-3, 24:5n-6, and 24:6n-3. Most n-6 PUFA (52% of total FA) were associated with the PL fraction; this was especially true for arachidonic and tetracosapentaenoic acids. The NL were enriched with mono-, di-, trienoic, and n-3 PUFA. The variation in EPA levels in both NL and PL suggests an origin of this acid from lipids of diatoms consumed by the corals.