Chemo-enzymatic synthesis and evaluation of novel structured phenolic lipids as potential lipophilic antioxidants



Chemo-enzymatic synthesis of structured triacylglycerol bearing ferulic acid as a phenolic acid at sn-1/3 position is described in the present work. Four compounds of varying chain lengths, namely 3-(4-hydroxy-3-methoxy-phenyl)-acrylic acid-2,3-bis-hexanoyloxy-propyl ester, 3-(4-hydroxy-3-methoxy-phenyl)-acrylic acid-2,3-bis-octanoyloxy-propyl ester, 3-(4-hydroxy-3-methoxy-phenyl)-acrylic acid-2,3-bis-dodecanoyloxy-propyl ester, and 3-(4-hydroxy-3-methoxy-phenyl)-acrylic acid-2,3-bis-9-octadecenoyloxy-propyl ester were synthesized, and their structures were confirmed by IR, NMR, and MS. Antioxidant activity of the structured phenolic lipids were evaluated using three different in vitro antioxidant assays such as 2, 2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging, antioxidant potency in lipid matrix using rancimat, and by the rate of inhibition of autoxidation of linoleic acid in micelles. Ferulic acid and dodecylgallate were used as reference antioxidant compounds. DPPH assay did not show any improvement in the antioxidant activity of ferulic acid with lipophilic modification. However, the antioxidant potency of the structured phenolic lipids measured by rancimat method as well as by the rate of inhibition of autoxidation of linoleic acid in micelle showed improvement in antioxidant activity compared to ferulic acid. This is probably due to better solubility of the synthesized phenolic lipids in a hydrophobic medium and appropriate anchorage in Tween 20 micelle. The observed activities of the structured phenolic lipids are comparable to dodecyl gallate in rancimat assay, but superior to dodecyl gallate in Tween 20 micellar system.