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.
Sciadonic acid (△5,11,14–20:3, SCA) is a rare versatile non-methylene-interrupted polyunsaturated fatty acid. To prepare high purity SCA from Torreya oils with 8.04 % purity, Ag + -assisted high-speed countercurrent chromatography (HSCCC) combined with urea complexation (UC) or argentation column chromatography (CC) was investigated. Results showed that n -hexane: acetonitrile (1:1, v/v) was suitable mobile phase for HSCCC, and SCA with purity of 23.74 % and recovery of 61.74 % (SCA purity>20 %) were obtained. When the Ag + addition was 0.50 %, one round of Ag + -HSCCC resulted in a recovery of SCA up to 95.38 % with purity around 21 %. It was believed that the enhanced performance originated from the reversible complexes between Ag + and C C in SCA through π-s * and d-π* bonds. Starting with low purity SCA of 8.04 %, HSCCC (23.74 %), UC (62.67 %), or Ag + -CC (60.41 % ) alone failed to produce SCA with high-purity (>90 %). However, Ag + -HSCCC combined with Ag + -UC or Ag + -CC yielded SCA with purities of 76.21 % and 97.74 %, and overall recovery of 21.38 % and 19.31 %, respectively. Thus, Ag + -HSCCC was an efficient method for the pre-enrichment of SCA, which could effectively facilitate coupling with UC, Ag + -CC or other PUFA purification techniques, resulted in significant improved purification performances.
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