An Ag+-assisted high-speed countercurrent chromatography and column chromatography for effective separating sciadonic acid from Torreya grandis oils

Abstract

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 CC 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.