Lipase‐catalyzed synthesis of triolein‐based sunscreens in supercritical CO2

Novozym® 435‐catalyzed transesterification of ethyl 4‐hydroxy‐3‐methoxy cinnamate (ethyl ferulate, EF) with triolein to form the ultraviolet (UV)‐absorbing lipids monoferuloylmonooleoyl‐glycerol (FMO) and feruloyl‐dioleoyl‐glycerol (FDO) has been conducted using supercritical CO2 (SC−CO2) batch reactions. The alcoholysis of 0.1 M EF with 0.1 M 1‐octanol in SC−CO2 to form octyl ferulate was used as a model reaction to optimize pressure and temperature conditions. Conditions ranging from 45 to 80°C and 10.3 to 34.5 MPa (1,500 to 5,000 psi) were tested with a maximal conversion of 53% of the EF being achieved at 13.8 MPa (2,000 psi) and 80°C after 24 h. These optimized conditions applied to the transesterification of EF with triolein effected a combined FMO and FDO yield of 69%. Triolein exhibits higher solubilities in SC−CO2 at higher pressures; therefore, the transesterification was performed at 80°C over a range of pressures from 13.8 to 34.5 MPa (2,000 to 5,000 psi). Results showed that a maximal yield of 74% of FMO and FDO was reached at 80°C and 24.1 MPa (3,500 psi) after 48 h. Compared to the FMO and FDO synthesis conducted neat or in toluene, the synthesis of the UV‐absorbing lipids in SC−CO2 affords higher yields within a shorter amount of time. Therefore, the transesterification of EF with triolein in a SC−CO2 batch reaction is a viable route to UV‐absorbing lipids that could be used as active ingredients in sunscreen formulations.