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The enzymatic transesterification of selected phenolic acids with TAG, including trilinolein (TLA) and trilinolenin (TLNA), was investigated in an organic solvent medium. Maximal bioconversion of 66% was obtained with a dihydrocaffeic acid (DHCA) to TLA ratio of 1:2 after 5 d of reaction. Similarly, the highest bioconversion of 62% was obtained with a DHCA to TLNA ratio of 1:2, but after 12 d of reaction. However, a ratio of 1:4 DHCA/TLA decreased the bioconversion to 53%. Transesterification reactions of ferulic acid with both TAG, using a ratio of 1:2, resulted in low bioconversion of 16 and 14% with TLA and TLNA, respectively. The overall results indicated that bioconversion of phenolic MAG was higher than that of phenolic DAG. The structures of mono-and dilinoleyl dihydrocaffeate as well as those of mono-and dilinolenyl dihydrocaffeate were confirmed by LC-MS analyses. The phenolic lipids demonstrated moderate radical-scavenging activity. FIG. 2. HPLC chromatograms of the samples of the enzymatic transesterification reactions of DHCA with TLA (A and B) and trilinolenin (TLNA) (A′ and B′) monitored at 280 and 215 nm. Peak numbers were identified as follows: dihydrocaffeic acid, #1 and 1′; TLA, #7; TLNA, #7'; phenolic MAG, #2 and 2'; phenolic DAG, #5 and 5'; MAG, #3 and 3'; DAG, #6 and 6'; side reaction product, #4; and TLNA oxidation product, #8′. LIPASE-CATALYZED TRANSESTERIFICATION OF TRILINOLEIN AND TRILINOLENIN 105 JAOCS, Vol. 83, no. 2 (2006) FIG. 3. Atmospheric pressure chemical ionization MS analysis of monolinoleyl dihydrocaffeate (A), dilinoleyl dihydrocaffeate (B), monolinolenyl dihydrocaffeate (A'), and dilinolenyl dihydrocaffeate (B′). FIG. 4. Progress curves of the biosynthesis of phenolic MAG (I), phenolic DAG (I I), and total phenolic lipids (L) as well as the hydrolysis of TAG (L L) during the lipase-catalyzed transesterification of dihydrocaffeic acid with TLA (A) and TLNA (B).

The enzymatic synthesis of phenolic lipids by lipase-catalyzed transesterification of dihydrocaffeic acid (DHCA) with fish liver oil was investigated in a selected organic solvent medium. These synthesized phenolic lipids have potential use as nutraceutical products. Using a molar ratio of 1:8 DHCA to fish liver oil in hexane:2-butanone mixtures of 75:25 and 85:15 (v/v), the lipase-catalyzed reaction resulted in maximum conversion of 55.8 and 65.4%, respectively. The maximum conversion of phenolic monoacylglycerols in hexane:2-butanone mixture of 75:25 and 85:15 (v/v) was 40.3 and 37.7%, respectively; using the same solvent mixtures, the conversions of the phenolic diacylglycerol were 15.8 and 36.8%, respectively. Hexane:2-butanone mixture of 75:25 (v/v) was, therefore, the best organic solvent mixture for the production of phenolic monoacylglycerols, while that of 85:15 (v/v) was best for the production of phenolic diacylglycerols. The phenolic lipids produced from the fish liver oil and DHCA demonstrated antioxidant property as indicated by its free radical scavenging capacity.

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