γ-Linolenic acid (GLA), a precursor of arachidonic acid, possesses physiological functions of modulating immune and inflammatory response. Highly purified GLA is desired both as a medicine and as an ingredient of cosmetics. In this work, urea fractionation and lipase-catalyzed reactions were employed for the enrichment of GLA in borage oil. GLA content in free fatty acids from saponified borage oil can be increased from 23.6 to 94% by the method of urea fractionation. Partial hydrolysis of borage oil catalyzed by immobilized Candida rugosa lipase raises GLA content in the unhydrolyzed acylglycerols from 23.6 to 52.1%. The IM-60 catalyzed acidolysis reaction between the GLA-rich free fatty acid and the unhydrolyzed acylglycerols increases the GLA content in the acylglycerols from 52.1 to 75%. The acylglycerols in the reaction product contains ca. 90% triacylglycerol. The effects of temperature, water content, substrate weight ratio, and organic solvents on the GLA content in the acylglycerols were examined.Paper no. J8985 in JAOCS 76, 833-837 (July 1999).

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