Gas-Liquid Chromatographic Analysis of Indole-3-acetic Acid Myoinositol Esters in Maize Kernels

An improved method of fractionating the myoinositol esters of indoleacetic acid (IAA) from maize kernels by gas-liquid chromatography has been developed. Mass spectrometry was employed as an aid in identification of the esters. Maize kernels contain three groups of esters of IAA: (a) IAA myoinositols, (b) IAA myoinositol arabinosides, and (c) IAA myoinositol galactosides. Each group has three chromatographically distinguishable isomers. The glycosylinositols described are unique in that carbon 1 of the sugar is attached to the hydroxyl at C-5 of the myoinositol.     

Catalytic action of comicelles containing imidazolyl and hydroxyl groups in the hydrolysis of enantiomeric esters

The rate constants for hydrolysis of the enantiomers of amino acid p-nitrophenyl esters catalyzed by bifunctional comicellar catalysts containing the imidazolyl and hydroxyl groups have been determined at pH 7.30, 0.02 m phosphate buffer, and 25°C. The kinetic analysis suggests a reaction scheme which involves acylation followed by deacylation at the imidazolyl group. Although no appreciable cooperative catalytic efficiencies are observed between the bifunctional groups in the acylation step, it is found that the deacylation rates are thus accelerated by surfactant hydroxyl groups, and some of the stereoselective acyl transfer reaction occurs from the imidazolyl to the hydroxyl group in optically active comicellar systems.     

Kinetically controlled synthesis of monoglyceryl esters from chiral and prochiral acids methyl esters catalyzed by immobilized Rhizomucor miehei lipase

Partial acylation of only one primary hydroxyl group of glycerol generates a chiral center at position 2. Rhizomucor miehei lipase (RML) catalyzes the kinetically controlled transesterification of different aromatic carboxylic acids methyl esters with glycerol. High synthetic yields of glyceryl esters (around 70-80%) were obtained even in the presence of significant concentrations of water (from 5% to 20%). After a long incubation of the reaction mixture in the presence of the biocatalyst only pure free acid was obtained. Other lipases (from Geobacillus thermocatenulatus and from Thermomyces lanuginose) also catalyzed similar kinetically controlled transesterifications although less efficiently. RML immobilized on Sepharose-Q showed a high activity and specificity, compared to the immobilization by other techniques, only producing monoglyceryl esters with all substrates. In particular, monoglyceryl-phenylmalonate product was synthesized in 82% overall yield and >99% diastereomeric excess at pH 7.0 and 37 °C and 90% glycerol.     

Role of arginine in chemical cross-linking with N-hydroxysuccinimide esters

In order to clarify whether arginine has a promoting effect on the acylation of hydroxyl groups of serine, threonine, or tyrosine by homobifunctional cross-linking agents in aqueous solution, we carried out systematic experiments with model peptides, comparing relative reaction yields with covalently protected and unprotected arginines by MALDI-MS. The guanidinium group could be demonstrated to contribute to the reactivity of hydroxyl groups toward N-hydroxysuccinimide esters and catalyze the nucleophilic substitution, probably via hydrogen bonds.     

Enzymatic synthesis of sulphated flavonols in Flaveria

Cell-free extracts of Flaveria bidentis and F. chloraefolia catalysed the transfer of sulphate groups from 3′-phosphoadenosine-5′-phosphosulphate to the hydroxyl groups of a variety of hydroxylated and O-methylated flavonols, but not to flavones or phenylpropanoids. Enzymatic sulphation was more predominant at the 3-hydroxyl group, but not to the exclusion of other hydroxyl substituents on the flavonoid ring. Quercetin was sulphated to yield its mono-, di-, tri- and tetrasulphate esters. This, together with the differences observed in the sulphation of different flavonols by extracts of both Flaveria species, suggests the existence of a number of distinct, position-specific sulphotransferases (EC 2.8.2.-). The sulphation reaction was catalysed at an optimum pH of 7.5 in Tris-HCl buffer, required SH groups for activity and was stimulated in the presence of divalent cations.     

Phenolic O-methyltransferase from Lentinus lepideus (basidiomycete)

The fungus, Lentinus lepideus, produces crystalline methyl p-methoxycinnamate in stationary cultures. O-methylation and methyl ester formation of hydroxycinnamic acids were examined with enzyme preparations of the fungus. Using S-adenosylmethionine-¹⁴CH3, it was found that only the methyl esters of the hydroxycinnamic acids are substrates for O-methylation and not the free acids. Benzoic acids and their methyl esters are not substrates. The activity of the enzyme is p-specific and its specific activity decreases with increasing number of hydroxyl groups in the substrate. The same enzyme preparations catalyze the formation of the methyl ester of cinnamic acid from the free acid.     

Synthesis of N-hydroxycinnamoyl amide derivatives and evaluation of their anti-oxidative and anti-tyrosinase activities

Twelve N-hydroxycinnamoyl amino acid amide ethyl esters (CAES) were synthesized by using l-amino acid ethyl ester hydrochloride and corresponding cinnamic acid (ferulic acid, acetylferulic acid and caffeic acid) as raw materials in the presence of a catalytic amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide-hydrochloride (EDC) and 1-hydroxybenzotriene (HOBt). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activities of CAES were evaluated. The anti-tyrosinase activities of N-feruloyl amino acid ethyl esters and the hydroxyl (OH) free radical scavenging activities of N-caffeoyl amino acid ethyl esters were also examined. DPPH free radical scavenging activity was shown in all CAES, of which N-caffeoyl amino acid ethyl esters demonstrated higher radical scavenging activity than N-feruloyl amide derivatives, and (E) -N-(caffeic acid)-l-glycinate ethyl ester (c₅) had the strongest ability to scavenge free radicals with an IC₅₀ value of 18.6 µM. The acetylferuloyl amino acid esters exhibited the highest tyrosinase inhibition activity among the tested amides.     

Synthesis of 2-acetamido-1-N[N-(tert-butoxycarbonyl)-l-aspart-1-oyl-(l-phenylalanyl-l-serine methyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine and analogs

2-Acetamido-1-N-[N-(tert-butoxycarbonyl)-l-aspart-1-oyl-(l-phenylalanyl-l-serine methyl ester)-4-oyl]-2-deoxy-β-d-glucopyranosylamine and analogs containing d-glucopyranosyl, 4-O-β-d-glucopyranosyl-d-glucopyranosyl, l-Phe-l-Ala, and d-Phe-l-Ser were synthesized by condensation of glycosylamines having free hydroxyl groups with tripeptide esters activated with N-hydroxysuccinimide.     

Structure of indole-3-acetic acid myoinositol esters and pentamethyl-myoinositols

GC-MS properties of three isomeric esters of indole-3-acetic acid and myoinositol, three esters of indole-3-acectic acid and myoinositol arabinoside and three esters of indole-3-acetic acid and myoinositol galactoside are presented. MS fragmentation patterns for the four possible pentamethyl myoinositols are also shown. These data indicated that the arabinose, and galactose of the glycosides were in the pyranose form and that C-1 of the sugar was linked to the 5 hydroxyl of myoinositol. Homologies in fragmentation patterns for the esters and the glycoside esters, together with knowledge of the properties of 2-O-indole-3-acetyl-myoinositol, permitted identification of one of the arabinosides as 5-O-l-arabinopyranosyl-2-O-indole-3-acetyl-myoinositol and one of the galactosides as 5-O-d- galactopyranosyl-2-O-indole-3-acetyl-myoinositol. The remaining two GLC peaks observed for the arabinoside were then, most likely, the two mixtures of diastereoisomers 1 d- and 1 l-5-O-l-arabinopryranosyl-1-O-indole-3-acetyl myoinositol and 1 d- and 1 l-5-O-l-arabinopyranosyl-4-O-indole-3-acetyl-myoinositol. The remaining two GLC peaks observed for the galactoside would then be the 1 d and 1 l-5-O-d-galactopyranosyl-1-O-indole-3-acetyl-myoinositol and 1 d- and 1 l-5-O-d- galactopyranosyl-4-O-indoleacetyl-myoinositol.     

α2-Macroglobulin-like protein 1 can conjugate and inhibit proteases through their hydroxyl groups,because of an enhanced reactivity of its thiol ester

Proteins in the α-macroglobulin (αM) superfamily use thiol esters to form covalent conjugation products upon their proteolytic activation. αM protease inhibitors use theirs to conjugate proteases and preferentially react with primary amines (e.g. on lysine side chains), whereas those of αM complement components C3 and C4B have an increased hydroxyl reactivity that is conveyed by a conserved histidine residue and allows conjugation to cell surface glycans. Human α₂-macroglobulin–like protein 1 (A2ML1) is a monomeric protease inhibitor but has the hydroxyl reactivity–conveying histidine residue. Here, we have investigated the role of hydroxyl reactivity in a protease inhibitor by comparing recombinant WT A2ML1 and the A2ML1 H1084N mutant in which this histidine is removed. Both of A2ML1s'' thiol esters were reactive toward the amine substrate glycine, but only WT A2ML1 reacted with the hydroxyl substrate glycerol, demonstrating that His-1084 increases the hydroxyl reactivity of A2ML1''s thiol ester. Although both A2ML1s conjugated and inhibited thermolysin, His-1084 was required for the conjugation and inhibition of acetylated thermolysin, which lacks primary amines. Using MS, we identified an ester bond formed between a thermolysin serine residue and the A2ML1 thiol ester. These results demonstrate that a histidine-enhanced hydroxyl reactivity can contribute to protease inhibition by an αM protein. His-1084 did not improve A2ML1''s protease inhibition at pH 5, indicating that A2ML1''s hydroxyl reactivity is not an adaption to its acidic epidermal environment.     

Lipase/esterase-catalyzed synthesis of aliphatic polyesters via polycondensation: A review

Over the last decade, there has been an increasing interest in lipase/esterase-catalyzed polycondensation as an alternative to metal-based catalytic process, because the former can proceed under mild reaction conditions and does not cause undesirable side reactions or produce trace metallic residues. In this review, the in vitro synthesis of aliphatic polyesters by polycondensation using lipases or esterases is systematically summarized, especially for the synthesis of complex and well-defined polyesters. The polycondensation of diols with diacids or their activated esters, including alkyl, haloalkyl and vinyl esters, through esterification and transesterification polycondensation reactions is discussed. In addition, three or more monomers can also be polymerized simultaneously, which provides a new route for preparing functional polymers. Self-polycondensation with respect to hydroxyl and mercapto acids or their esters is another reaction mode discussed in the review. Finally, concurrent enzymatic ring-opening polymerization and polycondensation has been developed to construct novel polyesters with tailor-made structures and properties. Overall, the review demonstrates that lipase/esterase-catalyzed synthesis of polyesters via polycondensation provides an effective platform for conducting “eco-friendly polymer chemistry”.     

Epicuticular wax of Panicum virgatum

Leaf and stem wax of Panicum virgatum contains hydrocarbons (4%), esters (3%), free acids (2%), free alcohols (1%), triterpene alcohols (2%), β-diketones (69%) and hydroxy β-diketones (6%). Principal free alcohols range in chain length from C₂₆ to C₃₂. β-Diketones consist almost entirely of tritriacontane-12,14-dione and the hydroxy β-diketone consists only of 5(S)-5-hydroxytritriacontane-12,14-dione. The configuration of the hydroxyl group is the same as that of hydroxy β-diketones from festucoid grasses but opposite to that of the hydroxy β-diketone from Andropogon species.     

Nucleophilic addition of glycine esters to Gd@C82

The first investigation of nucleophilic addition of glycine esters to Gd@C₈₂ is reported and hydroxyl was found to compete with glycine esters in the reaction. The multiple adducts containing either mere glycine esters or both glycine esters and hydroxyl group were identified by MALDI TOF mass spectrometry and characterized with UV-Vis-NIR spectrometry. Because glycine ethyl ester is more soluble than glycine methyl ester in alcohol and toluene, as many as eight glycine ethyl ester groups can be added to the metallofullerene cage while the maximal number for glycine methyl ester groups is only four.     

Synthesis of Ester Oligomer by Aspergillus niger Lipase

Lipase from Aspergillus niger NRRL 337 catalyzed the synthesis of esters from various dicarboxylic acids and diols. Among the esters synthesized, those from 1,13-tridecanedioic acid and 1,3-propanediol were separated by gel permeation chromatography. The constitution of the purified ester was determined by using IR and MS. The dominant components of synthesized esters were pentamer and heptamer, and both end groups of the pentamer and heptamer were hydroxyl.

The possible reaction sequence in synthesis of ester oligomer by Aspergillus niger lipase is described.     

Synthesis of 3-O-acyl esters of serine and threonine

The 3-O-acyl derivatives of serine and threonine have been prepared by reacting oleoyl chloride and palmitoyl chloride with N-t-butoxycarbonyl (N-T-BOC) serine and N-t-BOC threonine. The t-BOC group was removed by treatment with 4 N HCl in dioxane. The products were identified by proton magnetic resonance spectroscopy, infrared spectroscopy, elemental analysis and chromatographic properties. The O-acyl serines and O-acyl threonines were converted to their methyl esters by treatment with boron trifluoride in methanol and were converted to their dinitrophyl derivatives by treatment with dinitrofluorobenzen (DNFB). The yield of the dinitrophenyl derivatives was very high but the yield of methyl esters was low due mainly to methanolysis and loss of the fatty acyl group. The O-acyl serines and O-acyld threonines prepared will provide standards for researchers who are interested in identifying fatty acids esterified to serine and threonine hydroxyl groups in membrane proteins.     

Epicuticular waxes from Agropyron dasystachyum,agropyron riparium and Agropyron elongatum

Epicuticular waxes from whole plants of Agropyron dasystachyum var. psammophylum, A. riparium and A. elongatum contain hydrocarbons (5–8 %), long chain esters (12–15%) and free acids (2–5%). The major esters are C₃₄C₅₆ esters derived from C₁₆C₃₀ acids and alcohols (1-hexacosanol is the major alcohol) but C₃₁, C₃₃ and C₃₅ esters (3–11%) are also present. The latter esters are C₁₈ and C₂₀ acid esters of C₁₃ and C₁₅ 2-alkanols. A. dasystachyum wax contains 2% free alcohols, that of A. riparium contains 17% and that of A. elongatum 11% (1-hexacosanol is the major alcohol in each). Diesters (2%), C₈C₁₂ diols esterified by (E)-2-alkenoic acids, are present in A. riparium wax. Hentriacontane-14,16-dione is present: 29% in A. dasystachyum wax and 32% in A. riparium wax, but only 5% in A. elongatum wax. 25-Oxohentriacontane-14,16-dione forms 14% of A. dasystachyum wax and 27% of A. elongatum wax but the oxo β-diketones of A. riparium wax (5%) consist of both 10-oxo- and 25-oxohentriacontane-14,16-diones in the ratio 4:1. Hydroxy β-diketones of the waxes are 25- and 26-hydroxyhentriacontane-14,16-diones; in A. dasystachyum (20%) the ratio is 3:1, in A. elongatum (20%) the ratio is 9:1 but in A. riparium (5%) it is ca 1:2. The configuration of the hydroxyl group in the 26-hydroxy β-diketone is opposite to that in the 25-hydroxy derivative. The unusual composition of the oxygenated β-diketones of A. riparium confirms that this species should be regarded as separate from A. dasystachyum. Wax from A. elongatum also contains 4-hydroxy-25-oxohentriacontane-14,16-dione (4%) and an unusual oxo-β-ketol, 18-hydroxy-7,16-hentriacontanedione (2%), both these components are probably derived biosynthetically from the 25-oxo β-diketone which is the major component of this wax. Syntheses of racemic 18-hydroxy-7,16-hentriacontanedione and of a model β-ketol, 12-hydroxy-10-pentacosanone, are described.     

Novel and Highly Efficient Regioselective Route to Helicid Esters by Lipozyme TLL

Highly regioselective acylation of helicid with fatty acid vinyl esters catalyzed by the lipase from Thermomyces lanuginosus has been successfully performed for the first time. For the enzymatic caproylation of helicid, under the optimal conditions, initial reaction rate was 33.2 mM/h, and substrate conversion and regioselectivity were greater than 99%. In addition, the acyl recognition of the enzyme in the regioselective acylation of helicid was investigated. The results showed that although 6’-O-acyl derivatives of helicid were exclusively obtained with all the tested acyl donors, the enzymatic reaction rate varied widely with different acyl donors, presumably owing to their different interactions with the active site of the lipase. It is also interesting that the different configuration of only one hydroxyl group at C-3 in helicid couldn’t affect the lipase-catalyzed esterification and helicid has the same regioselectivity as that of D-glucose and arbutin.     

Enzymatic synthesis of 1,3-dihydroxyphenylacetoyl-sn-glycerol: Optimization by response surface methodology and evaluation of its antioxidant and antibacterial activities

In this study, the enzymatic synthesis of phenylacetoyl glycerol ester was carried out as a response to the increasing consumer demand for natural compounds. 1,3-dihydroxyphenylacetoyl-sn-Glycerol (1,3-di-HPA-Gly), labeled as “natural” compound with interesting biological properties, has been successfully synthesized for the first time in good yield by a direct esterification of glycerol (Gly) with p-hydroxyphenylacetic acid (p-HPA) using immobilized Candida antarctica lipase as a biocatalyst. Spectroscopic analyses of purified esters showed that the glycerol was mono- or di-esterified on the primary hydroxyl group. These compounds were evaluated for their antioxidant activity using two different tests. The glycerol di-esters (1,3-di-HPA-Gly) showed a higher antiradical capacity than that of the butyl hydroxytoluene. Furthermore, compared to the p-HPA, synthesized ester (1,3-di-HPA-Gly) exhibited the most antibacterial effect mainly against Gram + bacteria. Among synthesized esters the 1,3-di-HPA-Gly was most effective as antioxidant and antibacterial compound. These findings could be the basis for a further exploitation of the new compound, 1,3-di-HPA-Gly, as antioxidant and antibacterial active ingredient in the cosmetic and pharmaceutical fields.     

The analysis of biogenic amines in the thoracic nervous system of the locust,Schistocerca gregaria,by gas-chromatography negative ion chemical ionization mass spectrometry (GC-NICIMS)

Biogenic amines in single ventral thoracic nerve cords of the locust, Schistocerca gregaria, have been identified and quantified by an extraction-derivatization procedure involving their reaction with ditrifluoromethylbenzoyl chloride (DTFMB) in the aqueous phase followed by extraction into an organic solvent, hydrolysis of phenolic esters and conversion of free hydroxyl groups to trimethylsilyl ethers. Subsequent analysis of these DTFMB-TMS derivatives by GC-NICIMS revealed that the molecular ion carried most (> 60%) of the ion current which made the method highly specific and gave a limit of detection below the picogram level. This publication establishes unequivocally that the principal amines in locust ventral thoracic nerve cord are p-tyramine, p-octopamine, dopamine and noradrenaline. 5-Hydroxytryptamine was determined using a previously published GC-NICIMS technique (Markey et al., Biomed. Mass Spectromet. 7, 301–304, 1981).     

Targeting (cellular) lysosomal acid ceramidase by B13: Design,synthesis and evaluation of novel DMG-B13 ester prodrugs

Acid ceramidase (ACDase) is being recognized as a therapeutic target for cancer. B13 represents a moderate inhibitor of ACDase. The present study concentrates on the lysosomal targeting of B13 via its N,N-dimethylglycine (DMG) esters (DMG-B13 prodrugs). Novel analogs, the isomeric mono-DMG-B13, LCL522 (3-O-DMG-B13·HCl) and LCL596 (1-O-DMG-B13·HCl) and di-DMG-B13, LCL521 (1,3-O, O-DMG-B13·2HCl) conjugates, were designed and synthesized through N,N-dimethyl glycine (DMG) esterification of the hydroxyl groups of B13. In MCF7 cells, DMG-B13 prodrugs were efficiently metabolized to B13. The early inhibitory effect of DMG-B13 prodrugs on cellular ceramidases was ACDase specific by their lysosomal targeting. The corresponding dramatic decrease of cellular Sph (80–97% Control/1 h) by DMG-B13 prodrugs was mainly from the inhibition of the lysosomal ACDase.