Hydrolysis Of Methyl Ester Research Articles

Enantioselective enzymatic hydrolysis of racemic drugs by encapsulation in sol–gel magnetic sporopollenin

Candida rugosa lipase was encapsulated within a sol-gel procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of octyltriethoxysilane and tetraethoxysilane in the presence of magnetic sporopollenin. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e., the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of racemic naproxen methyl ester, mandelic acid methyl ester or 2-phenoxypropionic acid methyl ester that were studied in aqueous buffer solution/isooctane reaction system. The encapsulated magnetic sporopollenin (Spo-M-E) was found to give 319 U/g of support with 342% activity yield. It has been observed that the percent activity yields and enantioselectivity of the magnetic sporopollenin encapsulated lipase were higher than that of the encapsulated lipase without support. The substrate specificity of the encapsulated lipase revealed more efficient hydrolysis of the racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester than racemic mandelic acid methyl ester. It was observed that excellent enantioselectivity (E > 400) was obtained for encapsulated lipase with magnetic sporopollenin with an ee value of S-Naproxen and R-2 phenoxypropionic acid about 98%.

Poly(methyl malate) Nanoparticles: Formation, Degradation, and Encapsulation of Anticancer Drugs

PMLA nanoparticles with diameters of 150-250 nm are prepared, and their hydrolytic degradation is studied under physiological conditions. Degradation occurs by hydrolysis of the side chain methyl ester followed by cleavage of the main-chain ester group with methanol and L-malic acid as the final degradation products. No alteration of the cell viability is found after 1 h of incubation, but toxicity increases significantly after 3 d, probably due to the noxious effect of the released methanol. Anticancer drugs temozolomide and doxorubicin are encapsulated in the NPs with 20-40% efficiency, and their release is monitored using in vitro essays. Temozolomide is fully liberated within several hours, whereas doxorubicin is steadily released from the particles over a period of 1 month.

Total Synthesis of Synechoxanthin through Iterative Cross‐Coupling

Total Synthesis of Synechoxanthin through Iterative Cross‐Coupling

Overexpression of a bacterial chymotrypsin: Application for l-amino acid ester hydrolysis

In this work, a reliable protocol was designed to rapidly express and purify a microbial chymotrypsin(ogen) as a useful alternative to using animal proteases. The cDNA encoding for chymotrypsinogen from the deuteromycete Metarhizium anisopliae ( chy1) was overexpressed in an Origami2(DE3) E. coli strain deficient in thioredoxin reductase and glutathione reductase activities, thus possibly allowing disulfide exchange. By using a quick purification protocol, in which the hexahistidine tag was added at the C-terminal end of the protease, the recombinant CHY1 protein could be purified in a single step on an Ni-NTA column as a mixture of 19.5- and 15-kDa mature active forms and did not require further activation/maturation steps. This expression and purification procedure offers an easier and faster means of producing recombinant CHY1 chymotrypsin than that previously described for Pichia pastoris. The kinetic properties could be characterized and CHY1 chymotrypsin was demonstrated to efficiently catalyze N-acetylated l-phenylalanine and l-tyrosine methyl ester hydrolysis.

Improvement of catalytic activity of lipase from Candida rugosa via sol–gel encapsulation in the presence of calix(aza)crown

Lipase from Candida rugosa (CRL) was encapsulated within a chemically inert sol–gel support in the presence of calix(aza)crowns as the new additives. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenyl palmitate ( p-NPP) and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yields of the calix(aza)crown based encapsulated lipases were higher than that of the free lipase. Improved enantioselectivity was observed with the calix(aza)crown-based encapsulated lipases as compared to encapsulated free lipase. The reaction of Naproxen methyl ester resulted in 48.4% conversion for 24 h and 98% enantiomeric excess for the S-acid, corresponding to an E value of >300 ( E = 166 for the encapsulated free enzyme). Moreover, the encapsulated lipases were still retained about 18% of their conversion ratios after the sixth reuse in the enantioselective reaction.

Alkoxy-auxins Are Selective Inhibitors of Auxin Transport Mediated by PIN, ABCB, and AUX1 Transporters

Polar auxin movement is a primary regulator of programmed and plastic plant development. Auxin transport is highly regulated at the cellular level and is mediated by coordinated transport activity of plasma membrane-localized PIN, ABCB, and AUX1/LAX transporters. The activity of these transporters has been extensively analyzed using a combination of pharmacological inhibitors, synthetic auxins, and knock-out mutants in Arabidopsis. However, efforts to analyze auxin-dependent growth in other species that are less tractable to genetic manipulation require more selective inhibitors than are currently available. In this report, we characterize the inhibitory activity of 5-alkoxy derivatives of indole 3-acetic acid and 7-alkoxy derivatives of naphthalene 1-acetic acid, finding that the hexyloxy and benzyloxy derivatives act as potent inhibitors of auxin action in plants. These alkoxy-auxin analogs inhibit polar auxin transport and tropic responses associated with asymmetric auxin distribution in Arabidopsis and maize. The alkoxy-auxin analogs inhibit auxin transport mediated by AUX1, PIN, and ABCB proteins expressed in yeast. However, these analogs did not inhibit or activate SCF(TIR1) auxin signaling and had no effect on the subcellular trafficking of PIN proteins. Together these results indicate that alkoxy-auxins are inactive auxin analogs for auxin signaling, but are recognized by PIN, ABCB, and AUX1 auxin transport proteins. Alkoxy-auxins are powerful new tools for analyses of auxin-dependent development.

Immobilization of Candida rugosa lipase on magnetic sol–gel composite supports for enzymatic resolution of (R,S)-Naproxen methyl ester

In the present study, the Candida rugosa lipase (CRL) was encapsulated within a chemically inert sol–gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence and absence of magnetic Fe3O4 nanoparticles or sporopollenin with Fe3O4 as additive. The catalytic properties of the immobilized lipases were evaluated through model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of racemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicate that the sporopollenin based encapsulated lipase (Fe3O4-Spo-E) particularly has higher conversion and enantioselectivity compared to the encapsulated lipase without supports (lipase-enc). It has also been noticed that the sporopollenin based encapsulated lipase has excellent enantioselectivity (E = >400) as compared to the free enzyme (E = 166) with an ee value of ∼98% for S-Naproxen.

Improved Synthesis of (E)-12-Nitrooctadec-12-enoic acid, a Potent PPARγ Activator. Development of a “Buffer-Free” Enzymatic Method for Hydrolysis of Methyl Esters

Endogenous nitro-fatty acids, acting as partial agonist of PPARγ, are able to lower the insulin and glucose levels without the side effects associated with common antidiabetic drugs. (E)-12-Nitrooctadec-12-enoic acid, a potent activator of this peroxisome receptor, was synthesized in a very efficient sequence via a Henry-retro-Claisen ring fragmentation, followed by a novel enzymatic cleavage of methyl esters. The latter method was then applied in the last step of the synthesis of a few labile natural products, such as prostaglandins, isoprostanes, and phytoprostanes.

Immobilization of Candida rugosa lipase on glass beads for enantioselective hydrolysis of racemic Naproxen methyl ester

Candida rugosa lipase (CRL) was immobilized on glutaraldehyde-activated aminopropyl glass beads by using covalent binding method or sol-gel encapsulation procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)3 and Si(OCH3)4. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP). It has been observed that the percent activity yield of the encapsulated lipase was 166.9, which is 5.5 times higher than that of the covalently immobilized lipase. The enantioselective hydrolysis of racemic Naproxen methyl ester by immobilized lipase was studied in aqueous buffer solution/isooctane reaction system and it was noticed that particularly, the glass beads based encapsulated lipases had higher conversion and enantioselectivity compared to covalently immobilized lipase. In short, the study confirms an excellent enantioselectivity (E>400) for the encapsulated lipase with an ee value of 98% for S-Naproxen.

Kinetics of base hydrolysis of α-amino acid esters catalyzed by [Pd(Et4en)(H2O)2]2+

The kinetics of base hydrolysis of amino acid esters, glycine-, histidine-, and methionine methyl esters in the presence of [Pd(Et4en))(H2O)2]2+ is studied in aqueous solution at 25°C and I = 0.1 mol dm−1 (Et4en = N,N,N′,N′-tetraethylethylenediamine). The rate of ester hydrolysis for glycine methyl ester is studied at different temperatures and dioxane–water solutions of different compositions. The kinetic data fit a model which assumes that hydrolysis proceeds in one step. Hydrolysis of the esters is catalyzed by [Pd(Et4en)(H2O)2]2+ with catalysis ratio values of 2.5 × 104, 3.15, and 7.43 for glycine-, histidine-, and methionine methyl esters, respectively. Activation parameters for the base hydrolysis are evaluated.

Complex formation reactions of palladium(II)-1,3-diaminopropane with various biologically relevant ligands. Kinetics of hydrolysis of glycine methyl ester through complex formation

Abstract The interaction of [Pd(DAP)(H2O)2]2+ (DAP = 1,3-diaminopropane) with some selected bio-relevant ligands, containing different functional groups, were investigated. The ligands used are dicarboxylic acids, amino acids, peptides and DNA constituents. Stoichiometry and stability constants of the complexes formed are reported at 25°C and 0.1 M ionic strength. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants is examined. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. DNA constituents form 1:1 and 1:2 complexes. The effect of dioxane on the acid dissociation constants of CBDCA and the formation constant of its complex with Pd(DAP)2+ was reported. The kinetics of hydrolysis of glycine methyl ester bound to [Pd(DAP)(H2O)2]2+ was studied at 25°C and 0.1M ionic strength.

Kinetics of base hydrolysis of α-amino acid esters catalyzed by palladium(II) piperazine complex

Abstract The kinetics of base hydrolysis of glycine, histidine, and methionine methyl esters in the presence of [Pd(pip)(H2O)2]2+ complex, where pip is piperazine, is studied in aqueous solutions, at T = 25°C, and I = 0.1 mol dm−3. The rate of ester hydrolysis for glycine methyl ester is studied at different temperature and dioxane/water solutions of different compositions. The kinetic data are fit under the assumption that the hydrolysis proceeds in one step. The activation parameters for the base hydrolysis of the complexes are evaluated

Complex Formation Equilibria Between Zinc(II), Nitrilo-tris(Methyl Phosphonic Acid) and Some Bio-relevant Ligands. The Kinetics and Mechanism for Zinc(II) Ion Promoted Hydrolysis of Glycine Methyl Ester

Binary and ternary complexes of zinc(II) involving nitrilo-tris(methyl phosphonic acid (H6A) and amino acids, peptides (HL), or DNA constituents have been investigated. The stoichiometry and stability constants for the complexes formed are reported. The results show that ternary complexes are formed in a stepwise manner whereby nitrilo-tris(methylphosphonic acid) binds to zinc(II), which is then followed by coordination of an amino acid, peptide or DNA. Zinc(II) was found to form ZnA and ZnAH n complex species where n=3, 2 or 1. The stabilities of the ternary complexes are compared with the stabilities of their corresponding binary complexes. The concentration distributions of the various complex species have been evaluated. The kinetics of the base hydrolysis of glycine methyl ester in the presence of Zn(II)-NTP complexes was studied in aqueous solution using a pH-stat technique. The pK a for ionization of the coordinated water molecule is 9.14 as determined from the kinetic results, while direct potentiometric titration of the complex [Zn(NTP)(H2O)] gave 9.98 (±0.02). The rate constant for the intramolecular attack of coordinated hydroxide on the ester is k=(2.65×10−4±0.003) dm3⋅mol−1⋅s−1.

Enzymological Characteristics of Catalytic Antibody-catalyzed Enantioselective Hydrolysis of Ibuprofen Ester in Water-in-oil Microemulsion*

The asymmetric hydrolyzation of racemic ibuprofen ester is one of the most important methods for chiral separation of ibuprofen. A catalytic antibody that accelerates the rate of enantioselective hydrolysis of ibuprofen methyl ester was successfully elicited against an immunogen consisting of tetrahedral sulfate hapten attached to bovine serum albumin (BSA). The rate constant enhancement factor Kcat/Kuncat was about 1.6×104. The catalytic activity of the catalytic antibody in a reverse micelle reaction system based on sodium bis (2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane was studied. Kinetic analysis of the catalytic antibody-catalyzed reaction was found to be possible in this system. Kinetic studies showed that hydrolysis in the microemulsion system follow Michaelis-Menten kinetics. The catalytic antibody can also accelerate catalysis of S-ibuprofen methyl ester in the microemulsion system. Temperature effects, the pH profile, Km,app and Kcat were determined. The dependence of the catalytic antibody hydrolytic activity on the wo (molar ratio of water to surfactant) showed a bell-shaped curve, presenting a maximum at about wo = 21.

Enantioselective hydrolysis of rasemic naproxen methyl ester with sol–gel encapsulated lipase in the presence of sporopollenin

Sporopollenin is a natural polymer obtained from Lycopodium clavatum, which is highly stable with constant chemical structure and has high resistant capacity to chemical attack. In this study, the Candida rugosa lipase (CRL) was encapsulated within a chemically inert sol–gel support prepared by polycondensation with tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) in the presence and absence of sporopollenin and activated sporopollenin as additive. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate ( p-NPP), and the enantioselective hydrolysis of rasemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicated that the sporopollenin based encapsulated lipase particularly had higher conversion and enantioselectivity compared to the sol–gel free lipase. In this study, excellent enantioselectivity ( E > 400) has been noticed for most lipase preparations ( E = 166 for the free enzyme) with an ee value ∼98% for S-Naproxen. Moreover, ( S)-Naproxen was recovered from the reaction mixture with 98% optical purity.

Lithium Chloride–Assisted Selective Hydrolysis of Methyl Esters Under Microwave Irradiation

A rapid and mild method for the selective hydrolysis of methyl ester in lithium chloride–N,N-dimethylformamide (LiCl–DMF) system under microwave irradiation has been developed. The effects of substituent, metal salt, and solvent on the reactivity and selectivity of the hydrolysis reaction have been investigated. Microwave irradiation significantly improves the reaction yield within a short time in an LiCl–DMF system. Moreover, the chiral α-carbon of methyl esters retained its configuration during the reaction. Finally, the catalytic mechanism of hydrolysis by LiCl salt has also been proposed.

Equilibrium Studies on Complex‐Formation Reactions of Pd[(2‐(2‐aminoethyl)pyridine)(H2O)2]2+ with Ligands of Biological Significance and Displacement Reactions of DNA Constituents

AbstractThe [Pd(AEP)Cl2] complex was synthesized and characterized, where AEP = 2‐(2‐aminoethyl)pyridine. The stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents and dicarboxylic acids) and [Pd(AEP)(H2O)2]2+ were investigated at 25 °C and 0.1 M ionic strength. The equilibrium constants for the substitution of representative coordinated ligands such as inosine, glycine or methionine by cysteine were calculated and the concentration distribution diagrams of the various species evaluated. The kinetics of base hydrolysis of free and coordinated amino acid esters was investigated. The effects of the medium dielectric constant and temperature on the kinetics of base hydrolysis of the glycine methyl ester in the presence of the [Pd(AEP)(H2O)2]2+ complex were studied and the activation parameters ΔH≠ and ΔS≠ for the hydrolysis process were determined.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Enantioselective hydrolysis of (R/S)-Naproxen methyl ester with sol–gel encapculated lipase in presence of calix[ n]arene derivatives

Lipases are enzymes that catalyses a variety of reactions, such esterifications, interesterification and hydrolysis. Several methods have been reported for the immobilization of lipases, such as deposition onto solid supports, covalent binding and encapsulation within a polymer matrix or silica glasses obtained by sol–gel techniques. In this study, the Candida rugosa lipase was encapsulated within a chemically inert sol–gel support prepared by polycondensation by tetraetoxysilane (TEOS) and octyltrietoxysilane (OTES) in the presence and absence of calix[ n]arene, calix[ n]- NH 2 and calix[ n]- COOH ( n = 4, 6, 8) compounds as additives. The catalytic activity of the encapsulated lipases was evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate ( p-NPP), and the enantioselective hydrolysis of rasemic Naproxen methyl ester that was studied in aqueous buffer solution/isooctane reaction system. The results indicated that the particularly calix[4,6]- NH 2 and calix[6]- COOH based encapsulated lipases had higher conversion and enantioselectivity compared to the sol–gel free lipase.

Resolution of Ibuprofen Ester by Catalytic Antibodies in Water-miscible Organic-solvents

The asymmetric hydrolysis of racemic ibuprofen ester is one of the most important methods for chiral separation of ibuprofen. In this work, a catalytic antibody that accelerates the rate of enantioselective hydrolysis of ibuprofen methyl ester was obtained against an immunogen consisting of tetrahedral phosphonate hapten attached to bovine serum albumin (BSA). The catalytic activity of the catalytic antibody in the water-miscible organic-solvent system composed of a buffer solution and N, N-dimethylformamide (DMF) was studied. With 6% DMF in the buffer solution (containing catalytic antibody 0.25∼μmol, 0.2 mol·L −1 phosphate buffer, pH 8) at 37°C for 10 h, a good conversion (48.7%) and high enantiomeric excess (>99%) could be reached. The kinetic analysis of the catalytic antibody-catalyzed reaction showed that the hydrolysis in the water-miscible organic-solvent system with DMF in buffer solution followed the Michaelis-Menten kinetics. The catalytic efficiency ( K cat/ K m) was enhanced to 151.91 L·mmol −1·min −1, twice as large as that for the buffer solution only.

A versatile and selective chemo-enzymatic synthesis of β-protected aspartic and γ-protected glutamic acid derivatives

Two versatile, high yielding, and efficient chemo-enzymatic methods for the synthesis of β-protected Asp and γ-protected Glu derivatives using Alcalase are described. The first method is based on the α-selective enzymatic hydrolysis of symmetrical aspartyl and glutamyl diesters. The second method involving mixed diesters comprises a three-step protocol using (i) α-selective enzymatic methyl-esterification, (ii) chemical β-esterification, and finally (iii) α-selective enzymatic methyl ester hydrolysis. The yields of the purified β- and γ-esters range from 77% to 91%.