Chemoenzymatic synthesis and identification of medium- and long-chain triacylglycerol congeners

Medium- and long-chain triacylglycerols (MLCTs) offer rapid energy release and essential nutritional benefits, making them valuable in functional foods. In this study, MLCTs containing caprylic acid (C8:0; C) and linoleic acid (C18:2; L) were synthesized via a chemoenzymatic strategy combining lipase-catalyzed reactions and Steglich esterification. Four distinct MLCT congeners-CCL, CLC, LLC, and LCL-were obtained with yields of 52-67% (asymmetrical) and 71-84% (symmetrical), and purified using preparative HPLC (> 98%). The resulting compounds were structurally characterized by HPLC-ESI-MS and ¹³C NMR spectroscopy. HPLC-ESI-MS confirmed the expected mass-to-charge values for the [M + NH₄]⁺ adducts: 624.6 for CCL/CLC and 760.6 for LLC/LCL. ¹³C NMR analysis verified molecular symmetry; asymmetric TAGs showed three carbonyl signals (e.g., 173.30, 173.26, 172.88 ppm for CCL), while symmetric forms showed two signals. These results confirm the successful synthesis and structural integrity of MLCTs with defined fatty acid positioning for functional lipid applications.