Fractionation of blackcurrant seed oil

Abstract

Blackcurrant seed oil is known to be one of the richest natural sources of γ-linolenic (all cis-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 (all cis-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, from α-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 of α- and γ-linolenic acid, whereas stearidonic (all cis-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. © 1988 American Oil Chemists' Society.