Fractionation of blackcurrant seed oil

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Abstract
Blackcurrant seed oil is known to be one of the richest natural sources of γ‐linolenic (allcis‐6,9,12‐octadecatrienoic) acid, with values of up to 20% of this acid. These concentrations are sufficient for most applications of the oil, but some utilizations require higher concentrations of γ‐linolenic acid. Blackcurrant seed oil also contains up to 14%α‐linolenic (allcis‐9,12,15‐octadecatrienoic) acid. Different fractionation techniques have been evaluated to separate γ‐linolenic acid specifically from the other fatty acids present in the oil and, in particular, fromα‐linolenic acid.Distillation as well as fractionated crystallization at various temperatures did not give any reasonable results. Surprisingly enough, urea fractionation in methanol gives a specific separation ofα‐ and γ‐linolenic acid, whereas stearidonic (allcis‐6,9,12,15‐octadecatetraenoic) acid, which is present at around 3% in the blackcurrant seed oil, cannot be separated by urea fractionation.Stearidonic acid, like γ‐linolenic acid, has a double bond in the Δ6 position, which makes these two acids unique in this respect. This most probably explains their similar behavior toward urea‐occlusion.Further semi‐industrial preparative HPLC separations allowed us to obtain fractions of 95% γ‐linolenic acid.