Lipase-catalyzed synthesis of phytostanyl esters in non-aqueous media

Improved antioxidant activity of rutin via lipase-mediated esterification with oleic acid

BACKGROUND

Oxidation is a major problem for oils and fats, which can be mitigated by antioxidants. Rutin has excellent antioxidant activity, but its poor lipid solubility greatly limits its practical application. In this study, an efficient enzymatic synthesis route of lipophilic rutin ester was established using oleic acid as an acyl donor, and the antioxidant potential of rutin oleate was evaluated for the first time by proton (¹ H) nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

The synthesized product was finally identified as rutin oleate by Fourier transform infrared, high-performance liquid chromatography-mass spectrometry, and ¹ H, carbon-13, and DEPT-135 NMR analyses, and the acylation site was the 4‴-OH of the rhamnose group in the rutin molecule. The maximum conversion was over 93% after 48 h of reaction using Novozym 435 as catalyst under the best conditions among these tests. The conversion of rutin ester decreased with the increase of carbon chain length and the number of carbon-carbon double bonds of the fatty acid molecule. Most importantly, rutin oleate exhibited antioxidant capacity comparable to butylated hydroxytoluene and its counterparts (rutin and oleic acid) at low temperatures (60° C), but had a significant advantage at high temperatures (120° C).

CONCLUSION

The antioxidant activity of rutin was significantly enhanced by lipase-mediated esterification with oleic acid. Therefore, rutin oleate could be further developed as a novel antioxidant for use in oil- and fat-based foods. © 2023 Society of Chemical Industry.

Direct and selective enzymatic synthesis of trehalose unsaturated fatty acid diesters and evaluation of foaming and emulsifying properties

Trehalose diesters are Gemini-type surfactants that might have better surface activity than conventional surfactants. A one-step method for the preparation of trehalose unsaturated fatty acid diesters has been successfully developed. The yield of trehalose diester of different unsaturated fatty acids was between 78 % and 88 % under optimal conditions: 25 mmol/L trehalose, 100 mmol/L unsaturated fatty acid, 60 g/L 3 Å molecular sieves and 20 g/L lipase at 150 rpm and 50 °C for 42 h in 15 mL of acetone. Additionally, trehalose diester was the sole product obtained with Novozym 435 in acetone. The chemical structures of 6,6'-di-O-oleoyltrehalose, 6,6'-di-O-linoleoyltrehalose, 6,6'-di-O-eicosenoyltrehalose and 6,6'-di-O-erucoyltrehalose were confirmed by FTIR, MS and NMR. Moreover, the hydrophile-lipophile balance (HLB) values, foaming properties and emulsifying properties of trehalose diesters were assessed, showing the potentials of these diesters as naturally derived surfactants for the food industry.

Highly efficient synthesis of phytosterol linolenate in the presence of Bronsted acidic ionic liquid

Phytosterols are effective in reducing plasma cholesterol. However, phytosterols in a free form have some disadvantages because they have a high melting point and a poor oil solubility, thereby limiting their practical application in foods. The present study was to establish a green and highly efficient method to synthesize phytosterol linolenate for the first time by employing Bronsted acidic ionic liquid (IL) as a catalyst in order to improve its oil solubility. The product was separated, analyzed and subsequently characterized using thin layer chromatography, fourier transform infrared spectroscopy and mass spectroscopy. The conversion of phytosterols could reach above 96% in a very short time (30 min) under the following optimum conditions: 3% 1-butylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([BSO₃HMim]OTf) as a catalyst, 110 °C and 1:1.75 M ratio of phytosterols to ethyl linolenate. The present method demonstrated that [BSO₃HMim]OTf would be a potential catalyst for phytosterol ester synthesis. Most importantly was that the oil solubility of phytosterol linolenate was much greater than its corresponding free phytosterols.

Lipase-catalysed esters synthesis of cafestol and kahweol

Cafestol and kahweol (C&K), two coffee diterpene alcohols with structural similarity which exhibit anticarcinogenic effects, were isolated from green coffee Arabica beans, followed by their lipase-catalysed esterification and purification by preparative high-performance liquid chromatography (HPLC). The isolation and enzymatic synthesis parameters of C&K esters were studied, with the latter optimised by a Central Composite Design; both procedures were monitored by gas chromatography. Scale up and improved isolation conditions resulted in 1.29 g of C&K, with 98% purity from 300 g of green Arabica beans. The highest C&K ester yields were observed using an alcohol:fatty acid molar ratio of 1:5, 73.3 mg mL^-1 of CAL-B enzyme, 70 °C and 240 rpm for 3 days in toluene, leading to 85-88% conversion among a variety of tested C&K esters, including n-C_14:0-C_20:0, C_18:1, C_18:2 and C_18:3.

Immobilized lipase catalyzing glucose stearate synthesis and their surfactant properties analysis

Sugar fatty acid esters are practical importance and have a variety of applications that include surfactants and as an emulsifying agent. In this study, we report glucose stearate synthesis using lipase-Fe₃O₄ nanoparticles catalyst. The influence of various reaction factors, such as silica gel concentration, molar ratio of sugar/acid, reaction temperature and speed of agitation on esterification by immobilized enzyme was analyzed. The glucose stearate esterification degree of 87.2 % was obtained under the optimized condition: 1:2 molar ratio of glucose/stearic acid, 2 % (w/v) of silica gel at 120 rpm and 40 °C. Glucose esters were characterized according to their surfactant activity like emulsification index, oil displacement activity and antimicrobial activity. The results indicated glucose stearate acts as biosurfactant, with emulsification index of 66 % in mustard oil and oil displacement activity of 19.64 cm².

Efficient synthesis and characterization of ergosterol laurate in a solvent-free system

Ergosterol and its derivatives have attracted much attention for a variety of health benefits, such as anti-inflammatory and antioxidant activities. However, ergosterol esters are advantageous because this compound has better solubility than the free ergosterol. In this work, ergosterol laurate was efficiently synthesized for the first time by direct esterification in a solvent-free system. The desired product was purified, characterized by Fourier transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance, and finally confirmed to be ergosterol laurate. Meanwhile, the effect of various catalysts, catalyst dose, reaction temperature, substrate molar ratio, and reaction time were studied. Both the conversion of ergosterol and the selectivity of the desired product can reach above 89% under the selected conditions: sodium dodecyl sulfate + hydrochloric acid as the catalyst, 2:1 molar ratio of lauric acid/ergosterol, catalyst dose of 4% (w/w), 120 °C, and 2 h. The oil solubility of ergosterol and its laurate was also compared. The results showed that the solubility of ergosterol in oil was significantly improved by direct esterification with lauric acid, thus greatly facilitating the incorporation into a variety of oil-based systems.

An innovative auto-catalytic esterification for the production of phytosterol esters: experiment and kinetics

A safe, practicable and environmental friendly method was developed to synthesize phytosterol esters from phytosterols and long-chain fatty acids without adding any catalyst or solvent.

D-isoascorbyl palmitate: lipase-catalyzed synthesis, structural characterization and process optimization using response surface methodology

Background

Isoascorbic acid is a stereoisomer of L-ascorbic acid, and widely used as a food antioxidant. However, its highly hydrophilic behavior prevents its application in cosmetics or fats and oils-based foods. To overcome this problem, D-isoascorbyl palmitate was synthesized in the present study for improving the isoascorbic acid’s oil solubility with an immobilized lipase in organic media. The structural information of synthesized product was clarified using LC-ESI-MS, FT-IR, ¹H and ¹³C NMR analysis, and process parameters for high yield of D-isoascorbyl palmitate were optimized by using One–factor-at-a-time experiments and response surface methodology (RSM).

Results

The synthesized product had the purity of 95% and its structural characteristics were confirmed as isoascorbyl palmitate by LC-ESI-MS, FT-IR, ¹H, and ¹³C NMR analysis. Results from “one–factor-at-a-time” experiments indicated that the enzyme load, reaction temperature and D-isoascorbic-to-palmitic acid molar ratio had a significant effect on the D-isoascorbyl palmitate conversion rate. 95.32% of conversion rate was obtained by using response surface methodology (RSM) under the the optimized condition: enzyme load of 20% (w/w), reaction temperature of 53°C and D- isoascorbic-to-palmitic acid molar ratio of 1:4 when the reaction parameters were set as: acetone 20 mL, 40 g/L of molecular sieves content, 200 rpm speed for 24-h reaction time.

Conclusion

The findings of this study can become a reference for developing industrial processes for the preparation of isoascorbic acid ester, which might be used in food additives, cosmetic formulations and for the synthesis of other isoascorbic acid derivatives.

Enzymatic synthesis of feruloylated lysophospholipid in a selected organic solvent medium

Feruloylated lysophospholipids (FLPs) were firstly synthesized from phosphatidylcholine (PC) and ethyl ferulate (EF) using lipase-catalysed interesterification in selected solvents at controlled water content. Kinds of lipases and single solvents were screened. Novozym 435 and toluene were found to be the suitable biocatalyst and solvent, respectively. Then tert-butanol, n-butanol, chloroform, isopropanol, acetone and DMSO were respectively added into toluene in order to increase conversion of products. The results showed that toluene/chloroform could significantly increase the conversion and the optimal combination of toluene and chloroform was 90:10 (v/v). The optimal conditions generated for FLPs production were a substrate molar ratio of 5:1 (PC/EF), a PC's hydrolytic time of 1.5h, an enzyme load of 60 mg/ml, a solvent dosage of 5 ml and a molecular sieves concentration (4Å) of 100mg/ml. Under these conditions, 40.51% of EF can be converted to FLPs, which were identified by TLC and HPLC-MS.

Efficient solvent-free synthesis of phytostanyl esters in the presence of acid-surfactant-combined catalyst

An efficient approach based on the synthesis of phytostanyl esters with an acid-surfactant-combined catalyst in a solvent-free system was developed. The effect of catalyst dose, substrate molar ratio, reaction temperature, and acyl donor was considered. The reaction conditions were further optimized by response surface methodology, and a high yield of phytostanyl laurate (>92%) was obtained under optimum conditions: 3.17:1 molar ratio of lauric acid to plant stanols, 4.01% catalyst dose (w/w), 119 °C, and 4.1 h. FT-IR, MS, and NMR were adopted to confirm the chemical structure of phytostanyl laurate. Meanwhile, the physiochemical properties of different phytostanyl esters were investigated. Compared with phytostanols, the prepared phytostanyl esters had much lower melting temperature and higher oil solubility. There was no obvious difference in melting and solidification properties between sunflower oil with phytostanyl laurate (<5%) or oleate (<10%) and the original sunflower oil, suggesting that the esterification of phytostanols greatly facilitated their corporation into oil-based foods.

Ultrasonic pretreatment for lipase-catalyed synthesis of phytosterol esters with different acyl donors

This study is focused on the enzymatic esterification of phytosterols with different acyl donors to produce the corresponding phytosterol esters catalyzed by Canadia sp. 99-125 lipase under ultrasound irradiation. An ultrasonic frequency of 35 kHz, power of 200 W and time of 1h was determined to guarantee satisfactory degree of esterification and lipase activity. The influence of temperature, substrates concentration and molar ratio was investigated subsequently. The optimum production was achieved in isooctane system at 60°C with phytosterol concentration of 150 μmol/mL and phytosterol to fatty acid molar ratio of 1:1.5, resulting in a phytosterol esters conversion of above 85.7% in short reaction time (8h). Phytosterols esters could also be converted in high yields to the corresponding long-chain acyl esters via transesterification with triacylglycerols (above 90.3%) under ultrasound irradiation. In optimum conditions, the overall esterification reaction rate using the ultrasonic pretreatment process was above 2-fold than that of mechanical stirring process without damage the lipase activity.

Immobilization of Candida rugosa lipase on hydrophobic/strong cation-exchange functional silica particles for biocatalytic synthesis of phytosterol esters

In this work, mixed-mode silica particles functionalized with octyl and sulfonic acid groups was conveniently prepared by co-bonding a mixture of n-octyltriethoxysilane and 3-mercaptopropyltriethoxysilane and then oxidized with hydrogen peroxide. Candida rugosa lipase (CRL) was immobilized on the mixed-mode silica particles via hydrophobic and strong cation-exchange interaction. The resulting immobilized CRL increased remarkably its stability at high temperature in comparison to free CRL. The immobilized CRL was used as biocatalysts for enzymatic esterification of phytosterols with free fatty acids (FFAs) to produce phytosterol esters. The phytosterols linolenate esterification degree of 95.3% was obtained under the optimized condition. Phytosterols esters could also been converted in high yields to the corresponding long-chain acyl esters via transesterification with methyl esters of fatty acids (80.5%) or triacylglycerols (above 95.5%) using mixed-mode silica particles immobilized CRL as biocatalyst. Furthermore, the immobilized CRL by absorption retained 78.6% of their initial activity after 7 recycles.

Lipase-mediated synthesis of water-soluble plant stanol derivatives in tert-butanol

The effects of solvents with different log P values, and of lipases on the synthesis of water-soluble plant stanol derivatives were investigated. Results showed that conversion in solvents with log P<0.37 was mainly controlled by the hydrophobicity of the solvent and subsequent complete or partial deactivation of the enzyme. The solubility of substrate was the leading factor for the conversion in solvents with log P>0.37. Lipozyme RM IM and tert-butanol was the most suitable biocatalyst and solvent, respectively. The highest yield (>51%) of plant stanyl sorbitol succinate was obtained under the selected conditions: 50 μmol/mL plant stanyl hemisuccinate, 1:3 molar ratio of plant stanyl hemisuccinate to d-sorbitol, 80 mg/mL 3 Å molecular sieves and 100mg/mL Lipozyme RM IM in tert-butanol, 150 r/min and 55 °C. Fourier transform infrared spectroscopy, mass spectroscopy and nuclear magnetic resonance spectroscopy were adopted to determine the structure of product, suggesting that water-soluble plant stanol derivatives were successfully synthesized.

Cholesterol-lowering effects of plant steryl and stanyl laurate by oral administration in mice

The present study was conducted to investigate the efficacy of synthesized plant steryl and stanyl laurate in lowering the cholesterol level and to further examine the cholesterol-lowering potential of the free plant sterols and stanols dissolved in liquid emulsion on serum and liver lipids in mice by oral administration. Experimental results showed that both plant steryl and stanyl laurate could significantly decrease the serum levels of TC, LDL-C, LDL-C/HDL-C, and liver cholesterol contents and markedly increase fecal cholesterol concentrations but have no effect on serum TAG level, indicating that the produced plant steryl and stanyl laurate retained the cholesterol-lowering potential of natural plant sterols and stanols. However, no statistical difference in cholesterol-lowering efficacy was observed between plant steryl laurate and plant stanyl laurate, and free plant sterols and stanols dissolved in liquid emulsion could also significantly decrease serum cholesterol levels and markedly increase fecal cholesterol excretion. These results suggested that the esterified plant sterols/stanols had comparable effects to the free plant sterols/stanols in lowering serum TC levels but that they did gain a solubility advantage from the free plant sterols/stanols. Therefore, plant steryl/stanyl laurate could be considered as a potential nutraceutical or functional ingredient to reduce or prevent atherosclerosis and its related complications.