Abstract: The technic of extracting oil from evening primrose (Oenothera biennis L.cv."Laershan-1")seeds was studied by supercritical CO₂ extraction in orthogonal experiments. The optimal conditions were: extraction pressure 35 MPa, extraction temperature 30℃, separation temperature 35℃ and extraction time 60 min. Under optimal conditions, the yield is 23.1%. According to GC analysis, the main unsaturated fatty acid components of the oil include oleic acid,linoleic acid and γ-linolenic acid. Total content of unsaturated fatty acids is 91.93%. Analyses of physical-chemical parameters showed that acid number of the oil is very low, only 1.1 mg/g.

Key words: evening primrose oil, supercritical CO₂ extraction, γ-linolenic acid, Oenothera biennis L.