Enhancement of Enantioselectivity in the Bacillus subtilis Protease-catalyzed Hydrolysis of N-free Amino Acid Esters using the Ester Grouping-modification Approach

The generality of enantioselectivity enhancement through the modification of the alcohol moiety of a substrate ester was ascertained, for in the Bacillus subtilis protease-catalyzed hydrolysis of N-unprotected amino acid esters the enantioselectivity was enhanced largely by switching the conventional methyl ester to esters with a longer alkyl chain such as the isobutyl ester (from E = 3 to E = 130–170 in the case of 4-fluorophenylalanine esters) as in the enzymatic hydrolysis mediated by Aspergillus oryzae protease. There was indeed a profound dependence of E on the nature of the ester grouping.     

Synthetic esters recognized by glucuronoyl esterase from <Emphasis Type="Italic">Schizophyllum commune</Emphasis>

Glucuronoyl esterase is a novel carbohydrate esterase recently discovered in the cellulolytic system of the wood-rotting fungus Schizophyllum commune on the basis of its ability to hydrolyze methyl ester of 4-O-methyl-d-glucuronic acid. This substrate was not fully corresponding to the anticipated function of the enzyme to hydrolyze esters between xylan-bound 4-O-methyl-d-glucuronic acid and lignin alcohols occurring in plant cell walls. In this work we showed that the enzyme was capable of hydrolyzing two synthetic compounds that mimic the ester linkages described in lignin-carbohydrate complexes, esters of 4-O-methyl-d-glucuronic and d-glucuronic acid with 3-(4-methoxyphenyl)propyl alcohol. A comparison of kinetics of hydrolysis of methyl and 3-(4-methoxyphenyl)propyl esters indicated that the glucuronoyl esterase recognizes the uronic acid part of the substrates better than the alcohol type. The catalytic efficiency of the enzyme was much higher with the ester of 4-O-methyl-d-glucuronic acid than with that of d-glucuronic acid. Examination of the action of glucuronoyl esterase on a series of methyl esters of 4-O-methyl-d-glucopyranuronosyl residues α-1,2-linked to xylose and several xylooligosaccharides suggested that the rate of deesterification is independent of the character of the carbohydrate part glycosylated by the 4-O-methyl-d-glucuronic acid.     

The Collection and Elution of Radioactive Fatty Acid Methyl Esters During Quantitative Gas-Liquid Chromatography

Abstract

An improved procedure is described for the collection and elution of low levels of radioactive fatty acid methyl esters separated by gas-liquid chromatography. A gas chromatographic effluent splitter was employed to partition fatty acid methyl ester samples in the column effluent, Condensation of a portion of the eluted fatty acids was accomplished in borosilicate glass tubing collectors maintained at ?70°C, Quantitation of nanomolar levels of fatty acid methyl esters was accomplished by calibrating the gas chromatographic flame ionization detectors with the splitters opened or closed. The elution of condensed radioactive fatty acid methyl esters from the glass collectors was complete when benzene followed by a toluene based scintillation fluid were employed as solvents. The method described may be applicable to the analysis of cis-trans isomers of unsaturated fatty acids.     

Studies on Moss Spores. IV. Mass Spectrometric Identification of Saturated and Monoenoic Long Chain Fatty Acids in the Triglyceride Fraction of Polytrichum commune Spores

The saturated long chain fatty acid methyl esters of the triglyceride fraction of Polytrichum commune spores were separated by silver nitrate TLC and identified by a combination of gas chromatographic-mass spectrometric technique. The saturated fatty acid methyl esters were straight-chained, and even-numbered with carbon numbers ranging from 12 to 26 or odd-numbered with carbon numbers ranging from 13 to 25. The major components of the fraction containing saturated fatty acid methyl esters were methyl palmitate and methyl stearate. The fatty acid methyl esters of the monoenoic fraction isolated by silver nitrate TLC were converted to TMSO derivates which were analysed by gas chromatography-mass spectrometry. The analysis gave evidence of positional isomers. The fraction contained the following straight chain monoenoic fatty acid methyl ester isomers: methyl 7-cis-hexadecenoate, methyl 9-cis-hexadecenoate, methyl 9-cis-heptadecenoate, methyl 9-cis-octadecenoate, methyl 11-cis-octadecenoate, and methyl 11-cis-eicosenoate. The major components were methyl 9-cis-octadecenoate and methyl 7-cis-hexadecenoate.     

Activation of Protein Kinase C by Phorbol Esters and Arachidonic Acid Required for the Optimal Potentiation of Glutamate Exocytosis

Abstract: The effects of arachidonic acid and phorbol esters in the Ca²⁺-dependent release of glutamate evoked by 4-aminopyridine (4-AP) in rat cerebrocortical synaptosomes were studied. In the absence of arachidonic acid, high concentrations (500 n M ) of 4β-phorbol dibutyrate (4β-PDBu) were required to enhance the release of glutamate. However, in the presence of arachidonic acid, low concentrations of 4β-PDBu (1–50 n M ) were effective in potentiating glutamate exocytosis. This potentiation of glutamate release by phorbol esters was not observed with the methyl ester of arachidonic acid, which does not activate protein kinase C. Moreover, pretreatment of synaptosomes with the protein kinase inhibitor staurosporine also prevented the stimulatory effect by arachidonic acid and phorbol esters. These results suggest that the activation of protein kinase C by both arachidonic acid and phorbol esters may play a role in the potentiation of glutamate exocytosis.     

In situ lipase-catalyzed reactive extraction of oilseeds with short-chained dialkyl carbonates for biodiesel production

Dimethyl/diethyl carbonate was adopted as extraction solvent and transesterification reagent at the same time for in situ lipase-catalyzed reactive extraction of oilseeds for biodiesel production in this work. Fatty acid methyl esters and ethyl esters were respectively obtained with higher yields than those achieved by conventional two-step extraction/transesterification. The augment ranged from 15.7% to 31.7%. The key parameters such as solvent/seed ratio and water content were further investigated to find their effects on the in situ reactive extraction. The highest yields of Pistacia chinensis Bunge methyl ester, P. chinensis Bunge ethyl ester, Jatropha curcas L methyl ester and J. curcas L ethyl ester could attain 89.6%, 90.7%, 95.9% and 94.5%, respectively under the optimized conditions.     

Sterculic Acid and Its Analogues Are Potent Inhibitors of Toxoplasma gondii

Toxoplasmosis is a serious disease caused by Toxoplasma gondii, one of the most widespread parasites in the world. Lipid metabolism is important in the intracellular stage of T. gondii. Stearoyl-CoA desaturase (SCD), a key enzyme for the synthesis of unsaturated fatty acid is predicted to exist in T. gondii. Sterculic acid has been shown to specifically inhibit SCD activity. Here, we examined whether sterculic acid and its methyl ester analogues exhibit anti-T. gondii effects in vitro. T. gondii-infected Vero cells were disintegrated at 36 hr because of the propagation and egress of intracellular tachyzoites. All test compounds inhibited tachyzoite propagation and egress, reducing the number of ruptured Vero cells by the parasites. Sterculic acid and the methyl esters also inhibited replication of intracellular tachyzoites in HFF cells. Among the test compounds, sterculic acid showed the most potent activity against T. gondii, with an EC₅₀ value of 36.2 μM, compared with EC₅₀ values of 248-428 μM for the methyl esters. Our study demonstrated that sterculic acid and its analogues are effective in inhibition of T. gondii growth in vitro, suggesting that these compounds or analogues targeting SCD could be effective agents for the treatment of toxoplasmosis.     

Synthesis and Immunostimulating Activity of Cysteine-Containing Derivatives of Glycyrrhizic Acid

New cysteine-containing derivatives of glycyrrhizic acid were synthesized by its coupling with Cys(Bzl) esters or the Cys(Bzl)-Val-OBu ^t dipeptide by the active ester method (DCC/HOSu) or by Woodward's reagent K. The derivatives with Cys(Bzl) and Cys(Bzl)-Val residues attached to the carbohydrate part of the molecule stimulated the primary immune response and the reaction of delayed-Type hypersensitivity in mice at a dose of 2 mg/kg.     

Synthesis of mixed esters of ascorbic acid using methyl esters of palm and soybean oils

Mixed esters of ascorbic acid were synthesized using methyl esters of palm and soybean oils as acyl donors, in acetone at 50 degrees C, and catalyzed by Novozym 435. A conversion of 62% was obtained with palm oil methyl ester at an ascorbic acid to acyl donor molar ratio of 1:4; the mixed ester contained 45.89% ascorbyl palmitate, 42.59% ascorbyl oleate and 10.1% ascorbyl linoleate. Acylation with soybean oil methyl ester resulted in 17% conversion, yielding a mixed ester containing 10.08% ascorbyl palmitate, 20.68% ascorbyl oleate, and 64.96% of ascorbyl linoleate. The mixed esters of ascorbic acid can find direct use in food and cosmetics.     

A novel regulatory mechanism for amino acid absorption in lepidopteran larval midgut

A number of methyl and ethyl esters of naturally occurring amino acids exert a potent stimulatory effect on the cotransport system responsible for the absorption of most essential amino acids along the midgut of the silkworm Bombyx mori. L-Leucine methyl ester (Leu-OMe), one of the most effective activators, induces a large increase of the initial rate of leucine uptake in midgut brush border membrane vesicles (BBMV) from the anterior-middle (AM) region, and a small effect in BBMV from the posterior (P) region. Nonetheless, the methyl ester causes in both regions a relevant K(+)-, Deltapsi- and pH-independent increase of the intravesicular accumulation of the amino acid. The activation by Leu-OMe proves that amino acid absorption can be modulated all along the B. mori larval midgut and that the AM region, where the ability to transport and concentrate the substrate is very low, is more susceptible than the P region. Leucine uptake in AM-BMMV can be activated by amino acid methyl esters with definite structural requisites, with the following order of potency: L-leucine>L-phenylglycine>L-methionine>L-phenylalanine>L-norleucinez.Gt;L-isoleucine. The activation is stereospecific and occurs also with some ethyl esters (e.g. leucine and phenylalanine). No activation was observed with esters of amino acids with short hydrophobic or polar side-chains. The activation mechanism here described plays a fundamental role in larval growth since silkworms reared on artificial diets supplemented with leucine or methionine methyl esters reach maximum body weight 12-18 h before control larvae and spin cocoons with a larger shell weight. This novel regulatory mechanism of an amino acid transport protein appears to be widespread among lepidopteran larvae.     

Adverse effects of extracts of Artocarpus altilis Park,and Azadirachta indica (A. Juss) on the reproductive physiology of the adult female tick,Boophilus microplus (Canest.)

Summary

Adverse effects of extracts from the plants Artocarpus altilis and Azadirachta indica on egg laying and hatching in the tick Boophilus microplus were quantified. A 50% inhibition of egg laying was achieved by a dose of 0.54 and 0.46 μg crude ethanol extract per tick, respectively. These doses also caused a 65% and 80% hatching failure, respectively. Extracts, particularly those of A. indica, inhibit protein and lipid sequestration by ovaries and oocytes. GC-MS analyses revealed reductions in the quantities of four methyl esters sequestered from the ovaries into the oocytes oviposited on the 12th day of engorgement by the treated ticks in the order of (A. indica effects are in parentheses): undecanoic acid 10-methyl-,methyl ester 40% (100%); tetradecanoic acid, methyl ester 100% (100%); tetradecanoic acid, 12-methyl-,methyl ester 100% (100%) and pentadecanoic acid, 14-methyl-,methyl ester 30% (75%).     

Simultaneous quantitation of indole 3-acetic Acid and abscisic Acid in small samples of plant tissue by gas chromatography/mass spectrometry/selected ion monitoring

Indole 3-acetic acid (IAA) was analyzed in apple, orange, and prune tissue by GC-MS by monitoring the protonated molecular ion of its methyl ester at mass to charge ratio (m/z) 190 together with the major fragment ion at m/z 130 and the corresponding ions from the methyl esters of either [²H₄]IAA (m/z 194, 134) or [²H₅]IAA (m/z 195, 135). Abscisic acid (ABA) was analyzed by monitoring the major fragment ions of its methyl ester at m/z 261 and m/z 247 and the corresponding ions from the methyl ester of [²H₃]ABA (m/z 264, 250). Detection limits for IAA and ABA were 1 and 10 picograms, respectively using standards and 1 nanogram per gram dry weight for both phytohormones in plant tissue.     

Profiling the Lipophilic Fractions of Pithecellobium dulce Bark and Leaves Using GC/MS and Evaluation of Their Antioxidant,Antimicrobial and Cytotoxic Activities

Pithecellobium dulce has been used in traditional medicine to treat various ailments owing to its restorative properties. The biological activities and chemical profiles of the lipophilic fraction of P. dulce bark and leaves were assessed herein. Fatty acid methyl esters (FAME) and unsaponifiable matter (USM) were prepared and analyzed by GC/MS. A total of 40 compounds were identified in the bark saponifiable fraction, whereas 9 compounds were annotated in the leaves. Palmitic acid methyl ester was the major compound identified accounting for 41.48 % of the bark and 19.03 % of the leaves composition. Besides, linolenic acid methyl ester (22.40 %) and linoleic acid (12.69 %) were annotated in the leaves saponifiable fraction. A total of 63 compounds were detected in the bark USM and 4 compounds were identified in the leaves. Phytol represented the major component in the leaves (52.57 %) followed by lupeol (20.68 %) and lupenone (8.60 %). Meanwhile, n‐dodecane dominated in the bark USM accounting for 24.69 % of the total composition. The leaves and bark lipophilic fractions revealed moderate antioxidant and antibacterial activities. Both extracts showed no antifungal activity. No cytotoxicity was observed for both lipophilic fractions. P. dulce offers a good source of antioxidant compounds that can be introduced to food and pharmaceutical industry.     

The Synthesis of Some 5-Vinyluracil-Nucleoside Analogues

Abstract

The reaction of 5-iodouridine with esters of acrylic acid in the palladium-catalysed Heck reaction was used to generate a series of esters of the acid (E) -5- (2-carboxyvinyl)uridine in poor to moderate yield. An alternative method starts from the acid by protection of the sugar moiety followed by in situ generation of the acid chloride then ester formation followed by simultaneous sugar deprotection. Treatment of the methyl ester with ammonia and methylamine gave the corresponding amides, while treatment with dimethylamine gave 5-(1-dimethylamino-2-carboxy)ethyluridine as the major product.     

Structures of Monohydroperoxides Produced from Chlorophyll Sensitized Photooxidation of Methyl Linoleate

The effects on growth and mortality of larvae of pink bollworm (Pectinophora gossypiella, Saunders), bollworm (Heliothis zea, Boddie) and tobacco budworm (Heliothis virescens, F.) of adding selected C₁₀–C₁₂ fatty acid methyl esters to a standard diet were determined. The antibiotic activity of straight chain saturated esters was compared to the activity of esters with an olefinic bond either at C-2 or terminally or with a terminal acetylenic or cyclopropyl group. The ester with the greatest activity was the naturally occurring compound methyl (Z,Z)-deca-2,8-diene-4,6-diynoate (matricaria ester) which was lethal to all pink bollworm larvae at 0.01% in the diet and lethal to all bollworm and tobacco budworm larvae at 0.05%.     

Biochemical Effects of Fatty Acid and its Derivatives on l-Glutamic Acid Fermentation

It has been found that although Brevibacterium lactofermentum No. 2256 is incapable of accumulating l-glutamic acid in a biotin sufficient medium, it produces a large quantity of the acid in the presence of sucrose fatty acid ester. In a biotin deficient medium, however, the ester brought the unfavorable diminution of l-glutamic acid accumulation caused by the decrease of glucose consumption in an incubation period. The undesirable effects were practically lost when the ester was added to the culture medium after more than eight hours in the course of incubation. This fact suggests that the ester is concerned with the growth of microorganism. It is very interesting to elucidate the interrelation between sucrose fatty acid ester and biotin. For the maximum accumulation of l-glutamic acid corresponding increase in amount of the ester to the increasing concentration of biotin was necessary. The proportional relation did not extend to excedingly high levels of the two implicating factors. The further observations concerning the effects of the individual fatty acid esters such as sucrose stearate remain unsatisfactory.     

Curtius Rearrangement Using Ultrasonication: Isolation of Isocyanates of Fmoc-Amino Acids and Their Utility for the Synthesis of Dipeptidyl Ureas

An efficient conversion of N^α-[(9–fluorenylmethyl)oxy]carbonyl (Fmoc) amino acid azides to the corresponding isocyanates using ultrasound is described. The Curtius rearrangement was accomplished using acid azides in toluene solution as well as solid powder at room temperature. All isocyanates synthesized have been obtained as crystalline solids and were characterized. Coupling of isocyanates with amino acid methyl ester hydrochloride salts in presence of N-methylmorpholine (NMM) resulted in Fmoc-protected dipeptidyl urea esters, which have been well characterized by ¹H NMR, ¹³C NMR and mass spectrometry.     

Enantioselective Liquid–Liquid Extraction of Zopiclone With Mandelic Acid Ester Derivatives

Enantioselective liquid–liquid extraction of zopiclone was conducted by employing a series of (R)‐mandelic acid esters as chiral extractants. The effects of concentration of extractant, concentration of zopiclone, type of organic solvent, pH value, and temperature on the extraction efficiency were investigated. (R)‐o‐chloromandelic acid propyl ester was demonstrated to be an efficient chiral extractant for zopiclone resolution with a maximum enantioselectivity of 1.6. Chirality 25:952–956, 2013. © 2013 Wiley Periodicals, Inc.     

Resolution of racemic carboxylic acids via the lipase‐catalyzed irreversible transesterification of vinyl esters

The lipase‐catalyzed irreversible transesterification procedure using vinyl esters was applied to the resolution of racemic 2‐phenoxypropanoic acids. Aspergillus niger lipase showed high enantioselectivities and reasonable reaction rates. The enantioselectivity was found to be affected profoundly by several variables, e.g., the alcohol as nucleophile, the organic solvent used, and the reaction temperature. A gram‐scale resolution of (RS)‐2‐phenoxypropanoic acid was achieved after optimization of the reaction conditions. Then this irreversible transesterification procedure was applied to the resolution of some related 2‐substituted carboxylic acids. Thus, racemic 2‐methoxy‐2‐phenylacetic acid was resolved via the A. niger lipase‐catalyzed transesterification of the corresponding vinyl ester. 2‐Phenylpropanoic acid and 2‐phenylbutanoic acid were resolved using Pseudomonas sp. lipase. A gram‐scale resolution of 2‐phenylbutanoic acid was achieved by this procedure coupled with the porcine liver esterase‐catalyzed hydrolysis of the resulting methyl ester. Chirality 11:554–560, 1999. © 1999 Wiley‐Liss, Inc.     

Fatty acid composition of seeds of Satureja thymbra and S. cuneifolia

The chemical composition of fatty acid methyl esters (FAMEs) from seeds of S. thymbra and S. cuneifolia were analyzed by GC/MS. 7 FAMEs were identified from the seeds of S. thymbra mainly as 9-octadecenoic acid methyl ester (43.9%), hexadecanoic acid methyl ester (11.4%), 9,12,15-octadecatrienoic acid methyl ester (Z,Z,Z) (30.2%), and octadecanoic acid methyl ester (14.1%), while from the seed of S. cuneifolia 10 FAMEs were obtained with the main components, similar to S. thymbra. These were identified as 9-octadecenoic acid methyl ester (10.1%), hexadecanoic acid methyl ester (methyl palmitate, 34.6%), 9,12,15-octadecatrienoic acid methyl ester (Z,Z,Z) (6.3%) and octadecanoic acid methyl ester (1.8%).