Enzymatic synthesis of structured phenolic lipids by acidolysis of flaxseed oil with selected phenolic acids

Structured phenolic lipids were obtained by lipase-catalyzed acidolysis of flaxseed oil with selected phenolic acids, including hydroxylated and/or methoxylated derivatives of cinnamic, phenyl acetic and benzoic acids. Increasing the molar ratio of flaxseed oil to the selected phenolic acids from 4:1 to 8:1 resulted in an increase in the maximum bioconversion yield from the range of 5–60% to that of 7–74%, respectively. In addition, the bioconversion yield of phenolic lipids seemed to be dependent on the structure characteristics of phenolic acids and their electronic distribution. The highest bioconversion yield of 74% and 68% was obtained for the acidolysis of flaxseed oil with cinnamic and 3,4-dihydroxyphenyl acetic acids, respectively. Using p-coumaric acid as substrate, the bioconversion yield (45%) was higher compared to those obtained with ferulic and sinapic acids (19–29%). APCI-MS analyses confirmed the formation of seven cinnamoylated lipids, eight p-coumaroylated lipids and six 3,4-dihydroxyphenyl acetoylated lipids. The results also show that the acidolysis reaction resulted in an increase of C18:3 n-3 proportion from 53% in the original flaxseed oil to 60–72% in the phenolic lipids. Although the radical scavenging activity of 3,4-dihydroxyphenyl acetoylated lipids was lower than that of their phenolic acid component, it was close to that of α-tocopherol. However, p-coumaroylated lipids showed radical scavenging activity similar to that of coumaric acid.