Solvent-free enzymatic synthesis of 1,2-dipalmitoylgalloylglycerol: Characterization and optimization of reaction condition

A novel diacylglycerol-based galloyl structured lipid, 1,2-dipalmitoylgalloylglycerol (DPGG), was synthesized using the enzymatic transesterification of propyl gallate (PG) and tripalmitin under solvent-free condition. An immobilized and commercially available food-grade Candida antarctica lipase B, Lipozyme® 435, was used as the biocatalyst. The reaction variables that affect the yield of DPGG were optimized using a 33 full factorial design. At 70 °C, DPGG was obtained at a yield of 33.0 ± 2.0% with PG conversion at 44.8 ± 1.8% when the following condition was used: 25 substrate molar ratio of tripalmitin to PG, 120 h reaction time, and 25% enzyme load relative to the total substrate weight. The structure of reaction product was elucidated using Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization high-resolution accurate-mass tandem mass spectrometry (ESI-HRAM-MS/MS), and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). The effects of different lipases and galloyl donors/acceptors on the transesterification were also investigated.