Enzymatic synthesis of hydrophilic and hydrophobic derivatives of natural phenolic acids in organic media

Plant-derived and dietary phenolic cinnamic acid derivatives: Anti-inflammatory properties

Cinnamic acids are aromatic acids primarily found in plants and plant-derived food. Phenolic cinnamic acids, with one or more hydroxyl groups in the aromatic ring, often contribute to the biological activities attributed to these compounds. The presence of hydroxyl groups and a carboxyl group makes cinnamic acids very hydrophilic, preventing them from crossing biological membranes and exerting their biological activities. To alleviate this condition, a panel of synthetic modifications have been made leading to a diverse set of phenolic cinnamic structures. In this review, an overview of the natural phenolic cinnamic acid derivatives and their plant sources (more than 200) is described. The synthetic approaches to obtain the referred derivatives (more than 200) namely esters and amides are reviewed. Further, their anti-inflammatory activity (more than 70 compounds) is scrutinized. Finally, future directions will be indicated to translate the research on phenolic cinnamic derivatives into potentially effective anti-inflammatory drugs.

Functional groups matter: metabolomics analysis of Escherichia coli exposed to trans-cinnamic acid and its derivatives unveils common and unique targets

Phenolic acids are derivatives of benzoic and cinnamic acids, which possess important biological activities at certain concentrations. Trans-cinnamic acid (t-CA) and its derivatives, such as p-coumaric acid (p-CA) and ferulic acid (FA) have been shown to have antibacterial activity against various Gram-positive and -negative bacteria. However, there is limited information available concerning the antibacterial mode of action of these phenolic acids. In this study, we aimed to ascertain metabolic alterations associated with exposure to t-CA, p-CA, and FA in Escherichia coli BW25113 using a nuclear magnetic resonance (NMR)-based metabolomics approach. The results showed that t-CA, p-CA, and FA treatments led to significant changes (p < 0.05) in the concentration of 42, 55, and 74% of the identified metabolites in E. coli, respectively. Partial least-squares discriminant analysis (PLS-DA) revealed a clear separation between control and phenolic acid groups with regard to metabolic response. Moreover, it was found that FA and p-CA treatment groups were clustered closely together but separated from the t-CA treatment group. Arginine, putrescine, cadaverine, galactose, and sucrose had the greatest impact on group differentiation. Quantitative pathway analysis demonstrated that arginine and proline, pyrimidine, glutathione, and galactose metabolisms, as well as aminoacyl-tRNA and arginine biosyntheses, were markedly affected by all phenolic acids. Finally, the H2O2 content of E. coli cells was significantly increased in response to t-CA and p-CA whereas all phenolic acids caused a dramatic increase in the number of apurinic/apyrimidinic sites. Overall, this study suggests that the metabolic response of E. coli cells to t-CA is relatively different from that to p-CA and FA. However, all phenolic acids had a certain impact on oxidative/antioxidant status, genomic stability, arginine-related pathways, and nucleic acid metabolism.

From Hamamelitannin Synthesis to the Study of Enzymatic Acylations of D-Hamamelose

The bioactive natural substance, hamamelitannin, was effectively synthesized in two ways. The chemical acylation of 2,3-O-isopropylidene-α,β-D-hamamelofuranose promoted by Bu2SnO using 3,4,5-tri-O-acetylgalloyl chloride, followed by the deprotection provided hamamelitannin in 79%. Pilot enzymatic benzoylation of D-hamamelose using vinyl benzoate (4 equiv.) and Lipozyme TL IM as a biocatalyst in t-butyl methyl ether (t-BuMeO) gave mainly benzoylated furanoses (89%), of which tribenzoates reached (52%). Enzymatic galloylation of 2,3-O-isopropylidene-α,β-D-hamamelofuranose with vinyl gallate under the catalysis of Lipozyme TL IM in t-butyl alcohol (t-BuOH) or t-BuMeO provided only the 5-O-galloylated product. The reaction in t-BuMeO proceeded in a shorter reaction time (61 h) and higher yield (82%). The more hydrophobic vinyl 3,4,5-tri-O-acetylgallate in the same reactions gave large amounts of acetylated products. Vinyl gallate and triacetylgallate in the enzymatic acylation of D-hamamelose with Lipozyme TL IM in t-BuMeO yielded 2′,5-diacylated hamamelofuranoses in a yield below 20%. The use of other vinyl gallates hydrophobized by methylation or benzylation provided 2′,5-diacylated hamamelofuranoses in good yields (65–84%). The reaction with silylated vinyl gallate did not proceed. The best results were obtained with vinyl 2,3,5-tri-O-benzyl gallate, and the only product, 2′,5-diacylated hamamelofuranoside precipitated from the reaction mixture (84% in 96 h). After debenzylation, hamamelitannin was obtained an 82% yield from hamamelose in two steps. This synthesis is preparatively undemanding and opens the way to multigram preparations of bioactive hamamelitannin and its analogues.

Alkyl ferulic acid esters: Evaluating their structure and antibacterial properties

Ferulic acid (FA) is a natural antibacterial agent rich in plants, FA has excellent antioxidant and antibacterial properties. However, because of its short alkane chain and large polarity, FA is difficult to penetrate the soluble lipid bilayer in the biofilm to enter the cell to play an inhibitory role, limiting its biological activity. To improve the antibacterial activity of FA, with the catalytic condition of Novozym 435, four alkyl ferulic acid esters (FCs) with different alkyl chain lengths were obtained by fatty alcohols (including 1-propanol (C3), 1-hexanol (C6), nonanol (C9), and lauryl alcohol (C12)) modification. The effect of FCs on P. aeruginosa was determined by Minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), Growth curves, alkaline phosphatase (AKP) activity, crystal violet method, scanning electron microscopy (SEM), membrane potential, PI, cell contents leakage. Results showed that the antibacterial activity of FCs increased after esterification, and the antibacterial activity significantly increased and then decreased with the extension of the alkyl chain of the FCs. Hexyl ferulate (FC6) showed the best antibacterial activities against E. coli and P. aeruginosa (MIC for E. coli was 0.5 mg/ml, MIC for P. aeruginosa was 0.4 mg/ml). And Propyl ferulate (FC3) and FC6 showed the best antibacterial activities S. aureus and B. subtilis (MIC for S. aureus was 0.4 mg/ml, The MIC of B. subtilis was 1.1 mg/ml). In addition, the growth, AKP activity, bacterial biofilm, bacterial cell morphology, membrane potential and cell contents leakage of P. aeruginosa after different FCs were investigated, which found that FCs could damage the cell wall of P. aeruginosa and showed different effects on the P. aeruginosa cell biofilm. FC6 showed the best inhibition on the biofilm formation of P. aeruginosa cells, which caused the surface of P. aeruginosa cells to be rough and wrinkled. Some P. aeruginosa cells showed aggregation and adhesion, even rupture. The membrane hyperpolarization was obvious, which appeared as holes, leading to cell contents leakage (protein and nucleic acid). All these results concluded that the antibacterial activities FCs against foodborne pathogens depended on different fatty alcohol esterification of FA. FC6 showed the best inhibition on P. aeruginosa due to its effect on P. aeruginosa cell walls and biofilms and the leak of the cell contents. This study provides more practical methods and a theoretical basis for giving full play to the bacteriostatic effect of plant FA.

Enzymatic lipophilization of bioactive compounds with high antioxidant activity: a review

Food products contain bioactive compounds such as phenolic and polyphenolic compounds and vitamins, resulting in a myriad of biological characteristics such as antimicrobial, anticarcinogenic, and antioxidant activities. However, their application is often restricted because of their relatively low solubility and stability in emulsions and oil-based products. Therefore, chemical, enzymatic, or chemoenzymatic lipophilization of these compounds can be achieved by grafting a non-polar moiety onto their polar structures. Among different methods, enzymatic modification is considered environmentally friendly and may require only minor downstream processing and purification steps. In recent years, different systems have been suggested to design the synthetic reaction of these novel products. This review presents the new trends in this area by summarizing the essential enzymatic modifications in the last decade that led to the synthesis of bioactive compounds with attractive antioxidative properties for the food industry by emphasizing on optimization of the reaction conditions to maximize the production yields. Lastly, recent developments regarding characterization, potential applications, emerging research areas, and needs are highlighted.

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.

Versatile Synthesis of Organic Compounds Derived from Ascorbic Acid

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Ascorbic acid, also known as Vitamin C, is the most important vitamin observed in diverse food. Ascorbic acid has various applications in several fields. Studies have depicted that in organic synthesis, it can be used as a mediator or substrate. The derivatives of ascorbic acid have been found to possess numerous biological activities. In this review, we report the important derivatives of ascorbic acid, which have significant biological activities. Various studies are considered in this review to prove its wide range of availability.

Approaches for the enzymatic synthesis of alkyl hydroxycinnamates and applications thereof

Alkyl hydroxycinnamates (AHs) is a group of molecules of biotechnological interest due to their cosmetic, food, and pharmaceutical applications. Among their most interesting uses are as UV protectants, skin depigmentation agents, and antioxidant ingredients which are often claimed for their antitumoral potential. Nowadays, many sustainable enzymatic approaches using low-cost starting materials are available and interesting immobilization techniques are helping to increase the reuse of the biocatalysts, allowing the intensification of the processes and increasing AHs accessibility. Here a convenient summary of AHs most interesting biological activities and possible applications is presented. A deeper analysis of the art state to obtain AHs, focusing on most employed enzymatic synthesis approaches, their sustainability, acyl donors relevance, and most interesting enzyme immobilization strategies is provided.Key points• Most interesting alkyl hydroxycinnamates applications are summarized.• Enzymatic approaches to obtain alkyl hydroxycinnamates are critically discussed.• Outlook of enzyme immobilization strategies to attain alkyl hydroxycinnamates.

Comparative Analysis of Efficacy of Lactic Acid with Ferulic Peel (Combination Peel) Vs Ferulic Peel Alone as a Monotherapy for Photoaging

OBJECTIVES

Chemical peels are used to treat fine lines, photoaging, skin discoloration and scars. The objective of this study is to do a comparative analysis of lactic acid 30 % with ferulic peel 12 % (combination peel) versus ferulic peel 12% alone as a monotherapy for photoaging.

MATERIALS AND METHODS

This is a prospective study from Feb 2016 to 2020 in which a total of 60 female patients with ages between 25 and 36 years were treated. Randomization of patients was done for both groups with 30 patients enrolled in each group. The first group of 30 patients was treated with ferulic peel 12 % (hydroalcohol base) with L-ascorbic acid 15% as a sealer alone (i.e., Group A). In the second group, 30 patients were treated with lactic acid 30 % with ferulic peel 12% (hydroalcohol base) with L-ascorbic acid 15% as a sealer (combination peel) (i.e., Group B). Inclusion and exclusion criteria have been defined for the study. Two scales have been used for assessing the results, Allergan Skin Roughness Scale (ASRS) and Allergan Fine Line Scale (AFLS). ASRS and AFLS scores were assessed at pre-treatment (pre) and post-treatment (post 1 month after last peel session) and compared using Student's paired t test and independent t test.

RESULTS

The results showed significant and higher improvement of 27% and 42%, respectively, in ASRS (1.37 ± 0.49 vs. 1.87 ± 0.51, diff = 0.50, 95% CI = 0.24 to 0.76, p < 0.001) and AFLS (1.20 ± 0.41 vs. 2.07 ± 0.58, diff = 0.87, 95% CI = 0.61-1.13, p < 0.001) scores in patients treated with lactic acid and ferulic peel as compared to patients treated with ferulic peel alone. No complications were observed in our study.

CONCLUSION

The study found the combination of lactic acid and ferulic peel significantly more effective than ferulic peel alone in the management of fine lines, photoaging and skin discoloration. The findings of this study may need to be further validated on a larger sample size and multicentric analysis. Initial results of our 4-year study have yielded promising results.

LEVEL OF EVIDENCE III

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Chemoenzymatic Synthesis of New Aromatic Esters of Mono- and Oligosaccharides

An efficient and convenient chemoenzymatic route for the synthesis of novel phenolic mono-, di- and oligosaccharide esters is described. Acetal derivatives of glucose, sucrose, lactose and inulin were obtained by chemical synthesis. The fully characterized pure sugar acetals were subjected to enzymatic esterification with 3-(4-hydroxyphenyl) propionic acid (HPPA) in the presence of Novozyme 435 lipase as a biocatalyst. The aromatic esters of alkyl glycosides and glucose acetal were obtained with good esterification yields, characterized by mass spectrometry (MALDI-TOF MS), infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR). The synthesis of aromatic esters of disaccharide acetals was successful only for the enzymatic esterification of sucrose acetal. The new chemoenzymatic route allowed the synthesis of novel aromatic esters of inulin as the inulin monoacetal monoester and diester and the inulin diacetal monoester with a polymerization degree of two, as well as the inulin monoacetal monoester with a degree of polymerization of three, were obtained by enzymatic acylation of inulin acetals with HPPA. These compounds could represent a new class of sugar ester surfactants with enhanced bioactivity, antioxidative and antimicrobial properties and with potential application in drug delivery systems.

Interesterification of Egg-Yolk Phosphatidylcholine with p-Methoxycinnamic Acid Catalyzed by Immobilized Lipase B from Candida Antarctica

The p-methoxycinnamic acid (p-MCA) is one of the most popular phenylpropanoids, the beneficial impact of which on the human health is well documented in the literature. This compound has shown many valuable activities including anticancer, antidiabetic, and neuro- and hepatoprotective. However, its practical application is limited by its low bioavailability resulting from rapid metabolism in the human body. The latest strategy, aimed at overcoming these limitations, is based on the production of more stability in systemic circulation bioconjugates with phospholipids. Therefore, the aim of this research was to develop the biotechnological method for the synthesis of phospholipid derivatives of p-methoxycinnamic acid, which can play a role of new nutraceuticals. We developed and optimized enzymatic interesterification of phosphatidylcholine (PC) with ethyl p-methoxycinnamate (Ep-MCA). Novozym 435 and a binary solvent system of toluene/chloroform 9:1 (v/v) were found to be the effective biocatalyst and reaction medium for the synthesis of structured p-MCA phospholipids, respectively. The effects of the other reaction parameters, such as substrate molar ratio, enzyme dosage, and reaction time, on the degree of incorporation of p-MCA into PC were evaluated by use of an experimental factorial design method. The results showed that substrate molar ratio and biocatalyst load have significant effects on the synthesis of p-methoxycinnamoylated phospholipids. The optimum conditions were: Reaction time of three days, 30% (w/w) of Novozym 435, and 1/10 substrate molar ratio PC/Ep-MCA. Under these parameters, p-methoxycinnamoylated lysophosphatidylcholine (p-MCA-LPC) and p-methoxycinnamoylated phosphatidylcholine (p-MCA-PC) were obtained in isolated yields of 32% and 3% (w/w), respectively.

Biocatalytic Synthesis of Lipophilic Baicalin Derivatives as Antimicrobial Agents

Enzymatic acylation is commonly used to increase the lipophilicity of flavonoids. However, the absence of primary hydroxyl groups makes it challenging to acylate baicalin using traditional acylation methods. In this study, an enzymatic esterification strategy was developed to introduce fatty-acid chains into baicalin at its carboxyl group, hence successfully synthesizing a new series of baicalin ester derivatives in nonaqueous media. Under the optimal reaction conditions, up to 95% conversion of baicalin was achieved. Antimicrobial evaluation of the baicalin ester derivatives indicated a corresponding increase to that of C log P values, with a cutoff effect at C log P = 5.2. Baicalin ester derivatives with C log P values of 4.9-5.2 exhibited the most potent antimicrobial activity. Interestingly, the introduction of medium-length fatty alcohol chains not only increased lipophilicity but also endowed them with membrane-disrupting properties. This study, therefore, provides an understanding of the esterification of flavonoid glycosides and a prospective application of the ester derivatives.

Alkyl Ferulate Esters as Multifunctional Food Additives: Antibacterial Activity and Mode of Action against Escherichia coli in Vitro

This work aims to prepare ferulic acid alkyl esters (FAEs) through the lipase-catalyzed reaction between methyl ferulate and various fatty alcohols in deep eutectic solvents and ascertain their antibacterial activities and mechanisms. Screens of antibacterial effects of FAEs against Escherichia coli ATCC 25922 ( E. coli) and Listeria monocytogenes ATCC 19115 ( L. monocytogenes) revealed that hexyl ferulate (FAC6) exerted excellent bacteriostatic and bactericidal effects on E. coli and L. monocytogenes (minimum inhibitory concentration (MIC): 1.6 and 0.1 mM, minimum bactericidal concentration (MBC): 25.6 and 0.2 mM, respectively). The antibacterial mechanism of FAC6 against E. coli was systematically studied to facilitate its practical use as a food additive with multifunctionalities. The growth and time-kill curves implied the partial cell lysis and inhibition of the growth of E. coli caused by FAC6. The result related to propidium iodide uptake and cell constituents' leakage (K⁺, proteins, nucleotides, and β-galactosidase) implied that bacterial cytomembranes were substantially compromised by FAC6. Variations on morphology and cardiolipin microdomains and membrane hyperpolarization of cells visually verified that FAC6 induced cell elongation and destructed the cell membrane with cell wall perforation. SDS-PAGE analysis and alterations of fluorescence spectra of bacterial membrane proteins manifested that FAC6 caused significant changes in constitutions and conformation of membrane proteins. Furthermore, it also could bind to minor grooves of E. coli DNA to form complexes. Meanwhile, FAC6 exhibited antibiofilm formation activity. These findings indicated that that FAC6 has promising potential to be developed as a multifunctional food additive.

Developing a High-Temperature Solvent-Free System for Efficient Biocatalysis of Octyl Ferulate

Ferulic acid esters have been suggested as a group of natural chemicals that have the function of sunscreen. The study aimed to utilize an environmentally-friendly enzymatic method through the esterification of ferulic acid with octanol, producing octyl ferulate. The Box-Behnken experimental design for response surface methodology (RSM) was performed to determine the synthesis effects of variables, including enzyme amount (1000–2000 propyl laurate units (PLU)), reaction temperature (70–90 °C), and stir speed (50–150 rpm) on the molar conversion of octyl ferulate. According to the joint test, both the enzyme amount and reaction temperature had great impacts on the molar conversion. An RSM-developed second-order polynomial equation further showed a data-fitting ability. Using ridge max analysis, the optimal parameters of the biocatalyzed reaction were: 72 h reaction time, 92.2 °C reaction temperature, 1831 PLU enzyme amount, and 92.4 rpm stir speed, respectively. Finally, the molar conversion of octyl ferulate under optimum conditions was verified to be 93.2 ± 1.5%. In conclusion, it has been suggested that a high yield of octyl ferulate should be synthesized under elevated temperature conditions with a commercial immobilized lipase. Our findings could broaden the utilization of the lipase and provide a biocatalytic approach, instead of the chemical method, for ferulic acid ester synthesis.

Ultrasound irradiation promoted enzymatic alcoholysis for synthesis of monoglyceryl phenolic acids in a solvent-free system

Monoglyceryl phenolic acids (MPAs) were known as the natural hydrophilic antioxidants which could be used in different fields such as food, pharmaceutical, cosmetic etc. A novel enzymatic route of MPAs synthesis by the alcoholysis of phenolic acid ethyl esters with glycerol under ultrasound irradiation in solvent free system was developed. Optimization of reaction parameters shows that a high conversion of above 97.4% can be obtained under the following conditions: phenolic acid ethyl esters to glycerol molar ratio of 1:10, with 6% catalyst (Novozym 435), at 60°C and 200rpm, with ultrasound input of 250W, at 20kHz frequency. Compared to the conventional stirring method, the activation energy for phenolic acid ethyl esters conversion was decreased from 65.0kJ/mol to 32.1kJ/mol under ultrasound promotion; the apparent kinetic constant (V_m/K_m) increased above 1.2-folds; the lipase amount decreased to 50%; the time required for the maximum conversion reduced up to 3-folds without damaging the lipase activity, which is the fastest report for enzymatic synthesis of MPAs.

Biotransformation of Flavonoid Conjugates with Fatty Acids and Evaluations of Their Functionalities

Enzymatic conjugation with fatty acids including omega-3 polyunsaturated fatty acids (ω-3 PUFAs) derived from fish oil to three citrus fruit-derived flavonoids: grapefruit extract, naringin, and neohesperidin dihydrochalcone were investigated. The conversions were achieved over 85% under the catalysis of lipase Novozyme 435 in acetone at 45°C at semi-preparative scale. The conjugates were purified via solvent partition and silica gel chromatography and achieved 90–98% in purity. The NMR analysis of the conjugates confirmed that the fatty acid carbon chain was linked onto the primary –OH group on the glucose moiety of the flavonoids. The purified flavonoid conjugates alongside their original flavonoids were analyzed for antioxidant activities via 2,2-diphenyl-1-picrylhydrazyl scavenging assay, and anti-peroxidation test via peroxide values measured during a 1-week fish oil storage trial. Vascular endothelial growth factor (VEGF) assay was conducted with 1, 10, and 100 μM of naringin and grapefruits and their conjugates, respectively, and total VEGF levels were measured at 24 and 48 h, respectively, using ELISA and dot blot analysis. The results from these functionality experiments demonstrated that flavonoid FA conjugates have at least comparable (if not higher) antioxidant activity, anti-peroxidation activity, and anti-angiogenic activity.

Synthesis and in vitro antioxidant and antimicrobial studies of novel structured phosphatidylcholines with phenolic acids

Novel phenoylated phosphatidylcholines were synthesized from 1,2-dipalmitoyl phosphatidylcholine/egg 1,2-diacyl phosphatidylcholine and phenolic acids such as ferulic, sinapic, vanillic and syringic acids. The structures of phenoylated phosphatidylcholines were confirmed by spectral analysis. 2-acyl-1-lyso phosphatidylcholine was synthesized from phosphatidylcholine via regioselective enzymatic hydrolysis and was reacted with hydroxyl protected phenolic acids to produce corresponding phenoylated phosphatidylcholines in 48-56% yields. Deprotection of protected phenoylated phosphatidylcholines resulted in phenoylated phosphatidylcholines in 87-94% yields. The prepared compounds were evaluated for their preliminary in vitro antimicrobial and antioxidant activities. Among the active derivatives, compound 1-(4-hydroxy-3,5-dimethoxy) cinnamoyl-2-acyl-sn-glycero-3-phosphocholine exhibited excellent antioxidant activity with EC₅₀ value of 16.43μg/mL. Compounds 1-(4-hydroxy-3-methoxy) cinnamoyl-2-acyl-sn-glycero-3-phosphocholine and 1-(4-hydroxy-3,5-dimethoxy) cinnamoyl-2-palmitoyl-sn-glycero-3-phosphocholine exhibited good antioxidant activity with EC₅₀ values of 36.05 and 33.35μg/mL respectively. Compound 1-(4-hydroxy-3-methoxy) cinnamoyl-2-palmitoyl-sn-glycero-3-phosphocholine exhibited good antibacterial activity against Klebsiella planticola with MIC of 15.6μg/mL and compound 1-(4-hydroxy-3-methoxy) benzoyl-2-acyl-sn-glycero-3-phosphocholine exhibited good antifungal activity against Candida albicans with MIC of 15.6μg/mL.

Highly Efficient Synthesis of an Emerging Lipophilic Antioxidant: 2-Ethylhexyl Ferulate

Ferulic acid in ester form has shown a stronger ability in ameliorating certain pathological conditions and inhibiting lipid oxidation. In present study, a solvent-free and reduced pressure evaporation system was developed for lipase-catalyzed synthesis of 2-ethylhexyl ferulate (2-EF) from ferulic acid and 2-ethylhexanol. A Box-Behnken design with response surface methodology (RSM) and artificial neural network (ANN) was selected to model and optimize the process. Based on the yields of 2-EF, reaction temperature was shown to be the most important process factor on the molar conversion among all variables. The residual values and the coefficient of determination (R²) calculated from the design data indicated that ANN was better than RSM in data fitting. Overall, the present lipase-catalyzed approach for 2-EF synthesis at low reaction temperature in a reduced pressure evaporation system shows high 2-EF production efficiency. Notably, this approach can reduce the enzyme denaturation and ferulic acid oxidation that usually occur during long-term biosynthetic operations at high temperature.

Improvement on the Catalytic Performance Using Dual Lipases System in the Synthesis of Ferulate Esters

A novel approach of dual lipases system was successfully carried out in improving the synthesis of ferulate esters between ethyl ferulate and olive oil. Combination of Novozym 435 and Lipozyme RMIM were used as biocatalyst to improve the reaction performance. Different reaction parameters (ratio of lipases, reaction time, lipase dosage, substrate molar ratio and reaction temperature) were analyzed systematically. A high conversion of ferulate esters (85%) was obtained after 12 hrs of reaction time at optimal conditions of 1:9 w/w (Novozym 435/Lipozyme RMIM), 80 mg of lipase and 1:4 ethyl ferulate:olive oil at 60 oC.

Green and efficient production of octyl hydroxyphenylpropionate using an ultrasound-assisted packed-bed bioreactor

A solvent-free system to produce octyl hydroxyphenylpropionate (OHPP) from p-hydroxyphenylpropionic acid (HPPA) and octanol using immobilized lipase (Novozym® 435) as a catalyst in an ultrasound-assisted packed-bed bioreactor was investigated. Response-surface methodology (RSM) and a three-level-three-factor Box-Behnken design were employed to evaluate the effects of reaction temperature (x  1), flow rate (x  2) and ultrasonic power (x  3) on the percentage of molar production of OHPP. The results indicate that the reaction temperature and flow rate were the most important variables in optimizing the production of OHPP. Based on a ridge max analysis, the optimum conditions for OHPP synthesis were predicted to consist of a reaction temperature of 65°C, a flow rate of 0.05 ml/min and an ultrasonic power of 1.74 W/cm2 with a yield of 99.25%. A reaction was performed under these optimal conditions, and a yield of 99.33 ± 0.1% was obtained.

Phenylpropanoid glycoside analogues: enzymatic synthesis, antioxidant activity and theoretical study of their free radical scavenger mechanism

Phenylpropanoid glycosides (PPGs) are natural compounds present in several medicinal plants that have high antioxidant power and diverse biological activities. Because of their low content in plants (less than 5% w/w), several chemical synthetic routes to produce PPGs have been developed, but their synthesis is a time consuming process and the achieved yields are often low. In this study, an alternative and efficient two-step biosynthetic route to obtain natural PPG analogues is reported for the first time. Two galactosides were initially synthesized from vanillyl alcohol and homovanillyl alcohol by a transgalactosylation reaction catalyzed by Kluyveromyces lactis β-galactosidase in saturated lactose solutions with a 30%-35% yield. To synthesize PPGs, the galactoconjugates were esterified with saturated and unsaturated hydroxycinnamic acid derivatives using Candida antarctica Lipase B (CaL-B) as a biocatalyst with 40%-60% yields. The scavenging ability of the phenolic raw materials, intermediates and PPGs was evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) method. It was found that the biosynthesized PPGs had higher scavenging abilities when compared to ascorbic acid, the reference compound, while their antioxidant activities were found similar to that of natural PPGs. Moreover, density functional theory (DFT) calculations were used to determine that the PPGs antioxidant mechanism proceeds through a sequential proton loss single electron transfer (SPLET). The enzymatic process reported in this study is an efficient and versatile route to obtain PPGs from different phenylpropanoid acids, sugars and phenolic alcohols.