A Rapid and Practical Catalytic Esterification for the Preparation of Caffeic Acid Esters

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.

Identification and Antioxidant Abilities of Enzymatic-Transesterification (-)-Epigallocatechin-3-O-gallate Stearyl Derivatives in Non-Aqueous Systems

Vinyl stearate was added to enzymatic transesterification of (−)-Epigallocatechin-3-O-gallate (EGCG) to enhance its lipophilicity and antioxidant ability in a non-aqueous system. The lipase DF “Amano” 15 was used as the catalyst. The optimal reaction conditions were: acetonitrile as the solvent, the molar ratio of vinyl stearate: EGCG as 3:1, an enzyme amount of 4.0% (ratio of substrate mass), and a reaction temperature and time of 50 °C and 96 h, respectively, achieving 65.2% EGCG conversion. HPLC–MS and NMR were used to determine the structure of EGCG stearyl derivative (3″,5″-2-O-stearyl-EGCG). The lipophilicity of EGCG stearyl derivatives (3.49 ± 0.34) was higher (5.06 times) than that of the parent EGCG (0.69 ± 0.08). Furthermore, EGCG stearyl derivatives had excellent lipid oxidation compared with BHT, BHA, and parent EGCG. The POVs of soybean oil with EGCG stearyl derivatives (18.17 ± 0.92 mEq/kg) were significantly reduced (by 62.5%) at 21 d compared with those of EGCG (48.50 ± 1.23 mEq/kg). These results indicate that EGCG derivatives have broad antioxidant application prospects in lipophilic environments/high-fat food.

Lipophilized Epigallocatechin Gallate Derivative Exerts Anti-Proliferation Efficacy through Induction of Cell Cycle Arrest and Apoptosis on DU145 Human Prostate Cancer Cells

Epigallocatechin gallate (EGCG) is the predominant tea polyphenol and it exhibits a hydrophilic character. The lipophilized EGCG derivative (LEGCG) was synthesized by enzymatic esterification of EGCG with lauric acid to enhance its bioactivity. The tetralauroyl EGCG was confirmed by high-performance liquid chromatography-tandem mass spectrometry and further identified as 3', 5', 3″, 5″-4-O-lauroyl EGCG by 1H and 13C nuclear magnetic resonance. The anti-proliferation effect of LEGCG on DU145 human prostate carcinoma cells was evaluated by MTT assay. In addition, the underlying molecular mechanism by which LEGCG exerts anti-proliferation efficacy was elucidated by flow cytometry and immunoblot analysis. Results suggested that LEGCG exhibited a dose-dependent anti-proliferation effect on DU145 cells by G0/G1 phase arrest and induction of apoptosis. LEGCG induced cell cycle arrest via p53/p21 activation, which down-regulated the cyclin D1 and CDK4 expression. In addition, LEGCG induced apoptosis by increasing the Bax/Bcl-2 ratio, the cytochrome c release, and the caspases cleavage on DU145 cells. The results provide theoretical support to prevent prostate cancer with LEGCG.

Caffeates and Caffeamides: Synthetic Methodologies and Their Antioxidant Properties

Polyphenols are secondary metabolites of plants and include a variety of chemical structures, from simple molecules such as phenolic acids to condensed tannins and highly polymerized compounds. Caffeic acid (3,4-dihydroxycinnamic acid) is one of the hydroxycinnamate metabolites more widely distributed in plant tissues. It is present in many food sources, including coffee drinks, blueberries, apples, and cider, and also in several medications of popular use, mainly those based on propolis. Its derivatives are also known to possess anti-inflammatory, antioxidant, antitumor, and antibacterial activities, and can contribute to the prevention of atherosclerosis and other cardiovascular diseases. This review is an overview of the available information about the chemical synthesis and antioxidant activity of caffeic acid derivatives. Considering the relevance of these compounds in human health, many of them have been the focus of reviews, taking as a center their obtaining from the plants. There are few revisions that compile the chemical synthesis methods, in this way, we consider that this review does an important contribution.

Antiproliferative activity and SARs of caffeic acid esters with mono-substituted phenylethanols moiety

A series of CAPE derivatives with mono-substituted phenylethanols moiety were synthesized and evaluated by MTT assay on growth of 4 human cancer cell lines (Hela, DU-145, MCF-7 and ECA-109). The substituent effects on the antiproliferative activity were systematically investigated for the first time. It was found that electron-donating and hydrophobic substituents at 2'-position of phenylethanol moiety could significantly enhance CAPE's antiproliferative activity. 2'-Propoxyl derivative, as a novel caffeic acid ester, exhibited exquisite potency (IC₅₀=0.4±0.02 & 0.6±0.03μM against Hela and DU-145 respectively).