Rapid access to structured triacylglycerols acylated with n-3 polyunsaturated fatty acids for nutritional applications

A novel method for the synthesis of symmetrical triacylglycerols by enzymatic transesterification

A novel two-step enzymatic method is described in this study to synthesize symmetrical triacylglycerols (TAGs) with arachidonic acid (ARA) at the sn-2 position. The processes included the synthesis of 2-monoacylglycerols (2-MAGs) rich in 2-arachidonoylglycerol (2-AG) by enzymatic ethanolysis and the synthesis of symmetrical TAGs by enzymatic transesterification between 2-MAGs and vinyl palmitate. Under the optimal conditions, desired symmetrical TAGs were obtained at 89% yield. In this study, vinyl palmitate rather than palmitic acid was used as a novel acyl donor to react with 2-MAGs. It was the first study reporting the synthesis of symmetrical TAGs by enzymatic transesterification. The reaction using fatty acid vinyl ester as acyl donor is irreversible and temperature is low. Low-temperature reaction greatly suppressed the acyl migration of 2-MAGs and the irreversible reaction is much more effective compared to reversible reactions using free fatty acid and fatty acid ester as acyl donors.

The fraction of α-linolenic acid present in the sn-2 position of structured triacylglycerols decreases in lymph chylomicrons and plasma triacylglycerols during the course of lipid absorption in rats

Little is known about the ability of α-linolenic acid (Ln) to remain in the sn-2 position of TG during the absorption process. The goal of this study was to determine the Ln distribution in the lymph (Study 1) and plasma (Study 2) TG of rats fed a single i.g. load of structured TG [300 mg/rat of either oleic acid (O)/Ln/O TG (OLnO) or Ln/O/O TG (LnOO), n = 7 rats]. In an early fraction (3-4 h) of lymph (OLnO group; 100% Ln in the sn-2 position), 46 ± 2% Ln was maintained in this position in lymph TG. There was even less (29 ± 6%) in the last fraction (7-24 h) (P < 0.05). Ln was also found (9 ± 3%) in the sn-2 position of lymph TG in the LnOO group. The Ln content in lymph phospholipids was twice as high in rats when they were fed LnOO (4.2 ± 0.1%) than OLnO (2.3 ± 0.2%) (P < 0.005). Six hours postprandially (Study 2), 21 ± 3% of the Ln incorporated into plasma TG was located in the sn-2 position in the OLnO group compared to 13 ± 2% in the LnOO group (P < 0.001). Overall, these results indicate that the amount of Ln that moved from the sn-2 position of structured TG to the sn-1(3) position of lymph TG increased during absorption. This may account for a substantial hydrolysis of the 2-monolinolenylglycerols in enterocytes, leading to the intramolecular redistribution of Ln in lymph TG and, consequently, in plasma TG.