Combined Urea Complexation and Argentated Silica Gel Column Chromatography for Concentration and Separation of PUFAs from Tuna Oil: Based on Improved DPA Level
Eicosapentaenoic acid (EPA, 20:5n 3) docosapentaenoic acid (DPA) isomers (22:5n 6 and 22:5n 3) and docosahexaenoic acid (DHA, 22:6n 3) derived from tuna oil were concentrated by three stages of urea fractionation at various crystallization temperatures and different fatty acid/urea ratios. Thereafter, polyunsaturated fatty acids concentrate containing comparatively enriched DPA levels was purified by argentated silica gel column chromatography. A product containing 22.2 0.6 EPA, 4.6 0.0 DPAn 6, 5.9 0.1 DPAn 3 and 42.3 1.2 DHA was obtained at 1:1.6 fatty acid/urea ratio (w/w) by crystallization at 8 degC for 16 h, 20 degC for 8 h, and 8 degC for 16 h. A DPA isomer concentrate containing 26.1 0.5 DPAn 6 and 22.3 0.4 DPAn 3 was achieved by argentated silica gel chromatography in the 6 acetone/n hexane solvent fraction (v/v) and the recovery of both fatty acids was 66.1 3.2 and 70.7 2.2 respectively. Furthermore, 91.9 2.5 EPA and 99.5 2.1 DHA with recoveries of 47.8 2.0 and 56.7 3.3 respectively, were obtained in various fractions.