Silver ion assisted urea complexation for the enrichment of sciadonic acid from Torreya fargesii kernel oil

Sciadonic acid (SA), a unique polymethylene-interrupted polyunsaturated fatty acids from Torreya grandi, drew increasing attention due to its multi healthy function. The one-step preparation for high purity SA by using urea crystallization method assisted by silver ion was investigated. Silver(I) tied the triunsaturated SA to stay in solution, while urea crystallization drawn the saturated and monounsaturated oleic acid into its channel to form complexes, these bidirectional enrichment effects increased the purity of SA to 89.3 % from initial 9.95 % with SA recovery of 32 %. The 1:1 silver ion/SA molar ratio produced the optimal purification performances. Raman spectra analysis of various molar ratio silver complex with SA supported this finding. Optimization on inclusion parameters suggested that urea concentration of 40 %, the mass ratio of fatty acid ethyl ester to urea is 1:4, cool rate at 0.5 °C /min were fit. In addition, the recycling of silver ion, urea and ethanol was performed over four cycles, and the results showed that the purity and recovery of SA among cycles were stable, and the purification performances were acceptable. Therefore, the developed silver ion assisted urea complexation strategy for the preparation of high purity SA is simple, economic, effective and has the potential for application on scale.