Isolation of omega-3 polyunsaturated fatty acids (eicosapentaenoic acid - EPA and docosahexaenoic acid - DHA) from diatom biomass using different extraction methods

Abstract

The long chain omega-3 polyunsaturated fatty acids are essential for the proper functioning of human body. With an increasing demand for such products, an evaluation on the use of alternative sustainable sources of omega-3 fatty acids becomes extremely relevant. The present study concerned the isolation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from diatom biomass by different extraction methods. The first step concerned the optimization of the analysis method based on high-performance liquid chromatography - diode array detector (HPLC-DAD), and the evaluation of corresponding validation parameters. The developed method provided adequate limits of detection and quantitation, as well as appropriate criterion for reproducibility and linearity. Biomass samples harvested from cultures of Pseudostaurosira trainorii were pre-treated and submitted to Soxhlet extraction using methanol-chloroform, reflux extraction with acetone and supercritical fluid extraction (SFE) using 96% ethanol as co-solvent. Prior analysis, the extracts were subjected to derivatization process utilizing 2,4′-dibromoacetophenone in acetone andtriethylamine. The yielded derivatives were analyzed by HPLC-DAD and concentrations of EPA and DHA recovered from dry biomass were determined. The greatest content of omega-3 fatty acids was obtained for reflux extraction (EPA – 63.746 mg g−1, DHA – 1.379 mg g−1), followed by Soxhlet method (EPA – 39.729 mg g−1, DHA – 1.059 mg g−1) and SFE extraction (EPA – 33.701 mg g−1, DHA – 0.455 mg g−1). Although a lower fraction of fatty acids was recovered by using SFE, the obtained extracts present lower toxicity and may be directly applied to the development of daily products.