Lipase-catalyzed transesterification of dihydrocaffeic acid with flaxseed oil for the synthesis of phenolic lipids.

Lipase-catalyzed transesterification reaction of dihydrocaffeic acid (DHCA) with flaxseed oil in organic solvent media was investigated. Using equal molar concentration of DHCA and flaxseed oil, only phenolic monoacylglycerols were obtained with a transesterification yield (TY) of 18.9%. A 1:4 DHCA to flaxseed oil ratio resulted in the production of both phenolic mono and diacylglycerols, with TY of 39.6 and 27.8%, respectively. On the other hand, when 1:8 ratio of DHCA to flaxseed oil was used, the TY of phenolic diacylglycerols (46.0%) was higher than that of the phenolic monoacylglycerols (33.3%). The TY of phenolic diacylglycerols increased from 25.1 to 55.8%, when the ratio of the hexane/2-butanone reaction medium was changed from 65:35 to 85:25 (v/v); however, the TY of phenolic monoacylglycerols decreased slightly from 34.0 to 31.8%. The relative proportion of the C(18:3)n-3 was higher in the phenolic mono and diacylglycerols, 64.9 and 59.5%, respectively, as compared to the original flaxseed oil, 53.1%. The radical scavenging ability of phenolic lipids was significant; however, it was about half than that of alpha-tocopherol.