Obtaining EPA-rich polar lipids from microalga Nannochloropsis sp. by silica-gel chromatography using non-toxic solvents

Current research indicates that n-3 polyunsaturated fatty acids (PUFAs) bind to polar lipids (phospholipids and glycolipids) seem to exert a greater bioavailability compared to their neutral forms. The aim of this work was to obtain eicosapentaenoic acid (EPA) rich polar lipids from the saponifiable lipids (SLs) extracted from the microalga Nannochloropsis sp. (33.4 ± 0.1% of EPA; 60 ± 0.6% polar lipids) by fractionation using silica-gel columns and importantly, non-polar and polar (ethanol) non-toxic solvents. Nowadays, few studies have been conducted towards the extraction and purification of polar lipids. Firstly, the solvent type for obtaining the neutral saponifiable lipid (NSL) fraction (ethyl acetate, EA, butyl acetate, BA) and the SL/silica-gel, SL/BA, and SL/ethanol ratios were optimized in a small silica-gel cartridge (0.69 g silica gel). The optimized conditions were an SL/silica-gel ratio of 22.6 mg/g, an SL/BA ratio of 1.56 mg/mL and an SL/ethanol ratio of 0.312 mg/mL. Next, the fractionation scale was increased to a column containing 10 g of silica-gel. At this scale, a BA SL fraction was obtained with 96.2 ± 0.5% of NSLs, and an ethanol SL fraction containing 97.7 ± 0.3% of polar lipids and 44.9 ± 0.2% of EPA. In the ethanol fraction, 86.6 ± 0.2% of the polar lipids and 71.5 ± 0.4% of the EPA from the SL microalgal extract were recovered. Consequently, EPA-rich polar lipids were obtained at high yields and purities, which could be used as a source of n-3 PUFAs with greater bioavailability than those based on neutral lipids.