Structural characterization and antioxidant property of enzymatic-transesterification derivatives of (-)-epigallocatechin-3-O-gallate and vinyl laurate.

(-)-Epigallocatechin-3-O-gallate(EGCG) was enzymatically modified to enhance the lipophilicity and the antioxidant property. The determination of optimal reaction conditions are as follows: Lipase DF "Amano" 15 and acetone were used as catalyst and solvent, respectively. Equal molar of EGCG and vinyl laurate (1:1); lipase addition of 6.0% (w/w of total substrates); reaction temperature of 50°C and reaction time of 96 h, which obtained the conversion rate of EGCG at 80.1%. The structure of EGCG lauroyl derivatives were 5″-O-lauroyl-EGCG, 3″,5″-2-O-lauroyl-EGCG, and 5',3″,5″-3-O-lauroyl-EGCG, identified by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and nuclear magnetic resonance (NMR). Compared with the logP of precursor EGCG (0.69 ± 0.03), the logP of EGCG lauroyl derivatives was 1.37 ± 0.19, 2.27 ± 0.33, and 3.28 ± 0.37, increasing by 0.98, 2.28, and 3.75 times, respectively (p < 0.05), suggesting the grafted fatty acid chains make EGCG derivatives more lipophilic, and the lipid solubility gradually increased as the number of substituents increased. Furthermore, EGCG lauroyl derivatives had excellent lipid oxidation than that of EGCG. The POVs (peroxide values) of soybean oil with mono-, di-, tri-lauroyl EGCG were significantly reduced by 42%, 47%, and 57% than that of EGCG at 21 days, respectively, indicating the antioxidative inhibition of these derivatives decreased with the increase in substituents. This indicates that these derivatives have broad prospects of the antioxidant application while improving their solubility properties in lipophilic environments/high-fat food. Practical Application: The lipophilic esterification reaction of EGCG catalyzed by new catalytic lipase DF "Amano" 15 was carried out in a non-aqueous solvent.Various reaction factors on a higher conversion rate of EGCG lauroyl derivatives were evaluated. The lipophilicity and antioxidant properties of EGCG lauroyl derivatives were much excellent than that of parent EGCG.