Enzymatic incorporation of caffeoyl into castor oil to prepare the novel castor oil-based caffeoyl structured lipids

Lipase-catalyzed one-step regioselective synthesis of 1,2-dioctanoylgalloylglycerol in a solvent-free system: Optimization of reaction conditions and structural elucidation

A multi-functional galloylated structured lipid, 1,2-dioctanoylgalloylglycerol (DOGG), was synthesized enzymatically via a regioselective transesterification of propyl gallate and trioctanoate using an immobilized food-grade Candida antarctica lipase B (Lipozyme® 435) as the biocatalyst under solvent-free condition. The variables that affect the reaction, including reaction temperature, substrate ratio, reaction time, and enzyme load, were evaluated and optimized using Taguchi method and response surface methodology. Both methods predicted the same optimal reaction condition, resulting in a 68.8 ± 1.3% DOGG yield with reaction selectivity of 82.9 ± 0.6% at 90 °C, 25/1 trioctanoate/PG (mol/mol), 72 h reaction, and 25% enzyme load relative to the total substrate weight. The structure of the reaction product was elucidated using NMR spectroscopy and ESI-HRMS, confirming the regioselectivity of the reaction. Enzyme retained 50% of its activity after 5 cycles of reuse. It is feasible to synthesize DOGG as a potential antioxidant and nutraceutical using Lipozyme® 435.

Solvent-free enzymatic synthesis of 1,2-dipalmitoylgalloylglycerol: Characterization and optimization of reaction condition

A novel diacylglycerol-based galloyl structured lipid, 1,2-dipalmitoylgalloylglycerol (DPGG), was synthesized using the enzymatic transesterification of propyl gallate (PG) and tripalmitin under solvent-free condition. An immobilized and commercially available food-grade Candida antarctica lipase B, Lipozyme® 435, was used as the biocatalyst. The reaction variables that affect the yield of DPGG were optimized using a 3³ full factorial design. At 70 °C, DPGG was obtained at a yield of 33.0 ± 2.0% with PG conversion at 44.8 ± 1.8% when the following condition was used: 25 substrate molar ratio of tripalmitin to PG, 120 h reaction time, and 25% enzyme load relative to the total substrate weight. The structure of reaction product was elucidated using Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization high-resolution accurate-mass tandem mass spectrometry (ESI-HRAM-MS/MS), and 1D and 2D nuclear magnetic resonance spectroscopy (NMR). The effects of different lipases and galloyl donors/acceptors on the transesterification were also investigated.

Lipase-catalysed synthesis of mono- and di-acyl esters of glyceryl caffeate in propylene carbonate and their antioxidant properties in tuna oil

Development of new non-toxic antioxidants with diverse hydrophobic properties is important due to growing concerns about the toxicity of artificial oil-soluble antioxidants, the comparatively low effectiveness of natural options, and the complex role hydrophobicity plays in antioxidant effectiveness. Using caffeic acid, a naturally occurring phenolic acid with potent antioxidant activity, a range of glyceryl caffeate esters (decanoate and palmitate) were prepared using lipase-catalysed esterification reactions. Glyceryl-1-caffeate (GC) was prepared from ethyl caffeate and glycerol (acting as both the solvent and the substrate), catalysed by immobilised Candida Antarctica lipase B (Novozym-435) at 80 °C under vacuum. Esterification of GC with decanoic acid using immobilised Thermomyces lanuginosus lipase (TLIM) or Novozym-435 was found to be selective towards mono-acylated or di-acylated products, respectively. The reaction was performed in an unconventional solvent, propylene carbonate (PC), which has many of the attributes of a green solvent. Product conversions in PC were comparable to the best performing conventional solvents. In contrast to conventional volatile solvents, the low volatility of PC allowed the reaction to be performed under vacuum, without the need for molecular sieves for removal of water produced during the reaction. Diisopropyl ether was effective at extracting the more lipophilic products from PC. Both the lipase (Novozym-435) and PC were reused four times with only a small loss in conversion efficiency. Glyceryl caffeate esters performed much better than α-tocopherol at protecting bulk tuna oil from oxidation (analysed using Rancimat). A comparison of glyceryl caffeate esters (decanoate/palmitate and mono-/di-acylated) showed that their antioxidant effectiveness in bulk tuna oil was not affected by chain-length, but compounds containing only one fatty ester were slightly more effective than those containing two fatty esters.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

Influence of ionic liquid on Novozym 435-catalyzed the transesterification of castor oil and ethyl caffeate

Caffeic acid (CA), one kind of phenolic acids widely occurring in the plant kingdom, can be used as potential UV protective ingredient and antioxidant. However, the application of CA was limited because of its unsatisfactory solubility in hydrophilic and lipophilic media. In this work, BMIMPF₆, one kind of ionic liquids (ILs), was developed as an environmental friendly reaction media for the enzymatic preparation of CA derivatives by the transesterification of castor oil (CO) and ethyl caffeate (EC). Different series of ILs with BF 4 - , TF 2 - , and PF 6 - were screened and compared, and the effects of transesterification variables [temperature (60-100 °C) enzyme concentration (10-90 mg/mL), substrate molar ratio (CO/EC, 1:1-5:1), water load (0-8%), and reaction pressure] were also investigated. Results showed that, in the IL system, hydrophilic and lipophilic products were formed by two competitive reactions [(i) hydrolysis + transesterification and (ii) transesterification]. The maximum hydrophilic caffeoyl lipids yield (26.10 ± 0.28%) and reaction selectivity for hydrophilic caffeoyl lipids (0.4) was achieved in BMIMPF₆ system. The increases of substrate ratio (molar ratio of CO to EC, from 1:1 to 5:1), water load (from 0 to 8%), and enzyme concentration (from 10 to 90 mg/mL) were in favor of hydrophilic caffeoyl lipid formation. However, the vacuum system and high temperature (from 70 to 100 °C) are favorable for lipophilic caffeoyl lipids formation. Under the optimal reaction conditions (90 °C, 75 mg/mL enzyme concentration, substrate ratio 3:1, 60 h, and 10 mmHg vacuum pressures), the maximum EC conversion was 72.48 ± 2.67%. The activation energies of the transesterification, and the selective formations of lipophilic and hydrophilic products were calculated as 44.55, 47.65, and 54.96 kJ/mol, respectively.