Toru Ota

Stereospecific analysis of triacyl-sn-glycerols in Docosahexaenoic acid-rich fish oils

This paper presents the positional distribution of fatty acids in docosahexaenoic acid (22∶6n-3)-rich fish oil triacyl-sn-glycerols (TG). Stereospecific analysis of TG was carried out by a nonenzymatic method. The TG of bonito head oil, obtained after a winterization process, contained 22∶6n-3 at concentrations of 28,7, and 49 mole % in thesn-1,sn-2, andsn-3 positions, respectively. In the TG of oil before the winterization process, 22∶6n-3 was concentrated in thesn-3 position, followed evenly by thesn-1 andsn-2 positions. Tuna orbital oil, obtained after winterization, showed the preferential association of 22∶6n-3 to thesn-3 position, followed by thesn-1 position. This distribution pattern was similar to that observed for seal oil TG rather than sardine oil TG. The bonito head and tuna orbital oils are useful as fish oils with characteristics different from those of common fish oils, such as menhaden, sardine, and herring oils.

Antioxidative Activity of a Cathodic Solution Produced by the Electrolysis of a Dilute NaCl Solution

The effectiveness was evaluated of a cathodic solution prepared by the electrolysis of an NaCl solution in inhibiting the aqueous oxidation of ethyl linoleate and ethyl docosahexaenoate. The decrease in unoxidized substrate and the formation of total peroxides during oxidation indicate that the cathodic solution completely inhibited the oxidation of both ethyl esters, while these lipids were easily oxidized in an NaCl solution and in distilled water. The antioxidative activity of the cathodic solution was confirmed after open incubation for 3 days and 7 days at 37°C, although the scavenging ability of the cathodic solution toward DPPH radicals disappeared during this incubation.

Gas chromatographic separation of wax esters based on the degree of unsaturation

The wax esters of sperm whale head oil have been characterized by gas-liquid chromatography on an APOLAR 10C column according to their carbon number and number of double bonds. The novel technique permits the direct quantitative analysis of saturated and unsaturated wax esters.

Japanese Sardine Oil as a Source of 16:3(n-4) and 16:4(n-l) Fatty Acids

Open tubular gas liquid Chromatographic (GLC) analysis of fatty acids in Japanese sardine oil showed the contents of 1.57% hexadecatrienoic acid (16:3) and 2.55% hexadecatetraenoic acid (16:4). Concentrations of 16:3 and 16:4 were carried out through the urea adduct method, argentation thin layer chromatography (TLC) and reversed phase TLC, with the purities of 16:3 and 16:4 samples obtained being both higher than 92%. They were recognized as 16:3(n-4) and 16:4(n-1) by nuclear magnetic resonance analyses of the methyl esters and GLC analyses of the partially hydrazine hydrogenated products and their oxidative ozonolysis products. The structures were supported by the results of gas chromatographic-mass spectrometric analyses of the pyrrolidides. Other isomers of 16:3 and 16:4 have not been detected in the GLC analysis of the methyl esters. These results indicate that sardine oil is useful as a source of these fatty acids.

Positional distribution of 24∶6(n−3) in triacyl-sn-glycerols from flathead flounder liver and flesh

This paper presents the positional distribution of very long-chain fatty acids, 24∶6(n−3), in triacyl-sn-glycerols (TG) of flathead flounder (Hippoglossoides dubius). Each of the liver and flesh TGs was subjected to the stereospecific analysis. The liver TGs contained 24∶6(n−3) at concentrations of 1.5, 1.2 and 1.7 mole % in thesn-1,sn-2 andsn-3 positions, respectively, and the flesh TGs had 9.0, 7.8 and 7.1 mole % in thesn-1,sn-2 andsn-3 positions, respectively. This fatty acid was distributed almost evenly among the three positions of the TGs. No preference for thesn-2 position was observed in contrast to the general tendency for the distribution of longer-chain polyunsaturated fatty acids, such as 22∶6(n−3), 22∶5(n−3) and 20∶5(n−3). There was essentially no difference in the positional distributions of the liver and flesh TGs. The results obtained in this study give new fundamental information to the investigation of very long-chain fatty acids.

C20-C24 monounsaturated fatty acid isomers in the lipids of flathead flounder, Hippoglossoides dubius

Compositions of 20:1 and 22:1 isomers in the lipids of flathead flounder, Hippoglossoides dubius, fillets without skin were determined by open-tubular GLC of methyl esters and GC-MS of their dimethyl disulfide adducts. The principal 20:1 isomers were 20:ln-13 and 20:ln-11 (each 33% of total 20:1 isomers); whereas 20:ln-9 (18%), the dominant isomer in most fish, was not so important. The 22:1 isomers were dominated by 22:ln-11 (48% of total 22:1 isomers); this level was lower than that found in most fish. Other conspicuous 22:1 isomers were 22:1n-9 (28%) and 22:ln-13 (17%). Open-tubular GLC analysis of 24:1 isomers showed a predominance of 24:ln-9 (83% of total 24:1 isomers) as found in most fish. It is assumed that the unusual compositions of 20:1 and 22:1 isomers are directly related to the diets of flathead flounder.

Highly sensitive method for the separation of enantiomeric and regioisomeric diacylglycerols as 2-anthrylurethanes by chiral-phase high-performance liquid chromatography with fluorescence detection

Abstract A highly sensitive high-performance liquid chromatographic method was developed for the separation of enantiomeric 1,2- (S configuration) and 2,3-diacyl-sn-glycerols (R configuration) and regioisomeric 1,3-diacyl-sn-glycerols. For this purpose the diacylglycerols were converted to their 2-anthrylurethanes and subjected to chiral-phase HPLC with fluorescence detection. Satisfactory resolution of the enantiomers and regioisomers was achieved on a (R)-1-(1-naphthyl)ethylamine polymeric phase, using a mixture of n-hexane–dichloromethane–ethanol (150:10:1, v/v) as the mobile phase. The formation of various hydrogen bonding, dipole–dipole stacking and charge transfer complexes between the urethane derivatives and the stationary phase was thought to contribute to the enantiomer separation. The detection limit of 2-anthrylurethanes was 1 fmol when the signal-to-noise ratio was 3:1.

Enantiomer separations of secondary alkanols with little asymmetry by high-performance liquid chromatography on chiral columns

Enantiomer separations of secondary alkanols with little asymmetry, CH3(CH2)nCHOH(CH2)n + 1CH3, as their 3,5-dinitrophenylurethane (3,5-DNPU) derivatives were carried out by high-performance liquid chromatography (HPLC) using a chiral column Sumichiral OA-4100 containing N-(R)-1-(α-naphthyl)ethylaminocarbonyl-(S)-valine chemically bonded to silanized silica. Enantiomer separations (α = 1.06–1.07, Rs = 1.31–1.43) of 2-butanol, 3-hexanol and 4-octanol were obtained by HPLC at low temperature (− 20 to − 40°C). Enantiomer separation of 5-decanol (α = 1.02, Rs = 0.88) was obtained by HPLC at − 20°C after four recyclings. Enantiomer separations (α = 1.07–1.10, Rs = 1.05–1.28) of 2-butanol and 3-hexanol were obtained as 3,5-DNPU derivatives by HPLC using a YMC A-K03 chiral column containing (R)-1-(1-naphthyl)ethylamine polymer chemically bonded to spherical silica at ambient temperature.

Changes in positional distribution of fatty acids in dorsal muscle triacyl-sn-glycerols from chum salmon, Oncorhynchus keta, at spawning season☆

Positional distributions of fatty acids in dorsal muscle triacyl-sn-glycerols (TGs) were compared between the chum salmon, Oncorhynchus keta, caught on the coast and upstream at spawning season. The upstream salmon TGs contained 22:6 in the sn-1 and sn-3 positions at the concentrations higher than the coast salmon TGs. The level of it in the sn-2 position was not so different between them. The proportions of 16:0 in the sn-1 and sn-3 positions were much lower in the upstream salmon TGs than in the coast salmon TGs. The upstream salmon TGs also contained lower proportions of 20:5 in the sn-2 and sn-3 positions and of 16:1 in the sn-2 position. Such differences in positional distribution confirmed the view that the depletion of TGs occurred unevenly during the migration from coast to upstream. The uneven depletion of TGs was found to depend on the position in which the fatty acids are esterified.