Triglycerides (TG) consisting of highly purified (>97%) n-3 series highly unsaturated fatty acids, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), were administered to C57BL/KsJ-db/db mice for 4 weeks by pair-feeding to compare their effects on lipid metabolism and to evaluate the effects of DPA on lipid metabolism. The hepatic TG level and total amount was decreased by treatment with DHA and DPA compared to the control. The efficacy of DPA was greater than that of EPA, but less than that of DHA. In contrast, EPA had the greatest serum TG reducing effect. The hepatic cytosol fraction of the DHA-treated group contained the lowest fatty acid synthase (FAS) and malic enzyme (ME) activity levels. Furthermore, the DHA-treated group contained the highest serum adiponectin concentrations. These findings indicate that the strong hepatic TG-lowering effect of DHA is due to the suppression of TG synthesis. The same tendencies were observed in DPA-treated mice, and the effect was stronger than that observed in EPA-treated mice, but equivalent to that observed in DHA-treated mice. Based on these results, DPA possesses lipid metabolism-improving effects. The beneficial effects of DPA for lipid metabolism were not superior to those of EPA and DHA, and the effect was always intermediate between those of EPA and DHA.

We performed differential scanning calorimetry (DSC) and synchrotron radiation X‐ray diffraction (SR‐XRD) experiments of polymorphic structures and binary mixing characteristics of the enantiomers of 1‐oleoyl‐2,3‐dipalmitoyl‐sn‐glycerol (S‐OPP) and 1,2‐dipalmitoyl‐3‐oleoyl‐sn‐glycerol (R‐PPO). In the two enantiomers, oleic and palmitic acid moieties are asymmetrically connected at the sn‐1 and sn‐3 positions of the glycerol groups, with palmitic acid moiety at the sn‐2 position. Pure enantiomer samples (>99 %) were synthesized and employed throughout this study. The following results were obtained. (1) A basic feature of the mixture systems of S‐OPP and R‐PPO is of a eutectic nature due to different polymorphic structures of two enantiomers and the racemic compound of PPO (rac‐PPO). (2) Polymorphic behavior of S‐OPP and R‐PPO was quite similar, both having α‐2 and β′‐3, whereas rac‐PPO contained α rac‐3, β′rac‐2, and β′rac‐3. The DSC measurements showed that the melting points of β′‐3 (S‐OPP = 35.3 °C and R‐PPO = 34.9 °C) were higher than that of β′rac‐3 (31.0 °C). β was not crystallized in the pure enantiomers, and rac‐PPO. (3) αrac‐3 was crystallized at low cooling rates (~2 °C/min), whereas α‐2 of the two enantiomers was crystallized only with very rapid cooling (~10 °C/min). (4) Triple‐chain‐length structures were formed in αrac‐3, β′S‐3 (=β′R‐3), and β′rac‐3; α‐2 with a double‐chain‐length structure was formed in both enantiomers. These results indicate the importance of the relationship between subcell packing and glycerol conformation in the polymorphism and mixing characteristics of asymmetric unsaturated–saturated‐saturated mixed‐acid triacylglycerols.

In this study, supercritical fluid chromatography (SFC) coupled with triple quadrupole mass spectrometry was applied to the profiling of several regioisomeric triacylglycerols (TAGs). SFC conditions (column, flow rate, modifier) were optimized for the effective separation of TAGs. In the column test, a triacontyl (C30) silica gel reversed-phase column was selected to separate TAG regioisomers. Multiple reaction monitoring was used to selectively quantify each TAG. Then, the method was used to perform detailed characterization of a diverse array of TAGs in palm and canola oils. Seventy TAGs (C46:0-C60:2) of these oils were successfully analyzed as a result, and twenty isomeric TAG pairs were separated well. In particular, this method provided the fast and high resolution separation of six regioisomeric TAG pairs (PPLn/PLnP, PPL/PLP, PPO/POP, SPLn/SLnP, SPO/SOP, SSO/SOS-stearic acid (S, 18:0), oleic acid (O, 18:1), linoleic acid (L, 18:2), linolenic acid (Ln, 18:3), palmitic acid (P, 16:0)) in a short time (50min) as compared to high performance liquid chromatography. We were able to demonstrate the utility of this method for the analysis of regioisomeric TAGs in edible oils.

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