Identification and Characterization of a Mycobacterial (2R,3R)-2,3-Butanediol Dehydrogenase

Bacterial strain B-009, capable of using racemic 1,2-propanediol (PD), was identified as a rapid-growing member of the genus Mycobacterium. The strain is phylogenetically related to M. gilvum, but has slightly different physiological characteristics. An NAD⁺-dependent enantioselective alcohol dehydrogenase, which acts on R-PD, was purified from the strain. The enzyme was a homodimer of a peptide coded by a 1047-bp gene (mbd1). A highly conserved sequence for medium-chain dehydrogenase/reductases with a preference for secondary alcohols was found in the gene. Hydroxyacetone was produced from R-PD by an enzymatic reaction, indicating that position 2 of the substrate was oxidized. The enzyme activity was highest for (2R,3R)-2,3-butanediol (R,R-BD), enabling the enzyme to be identified as (2R,3R)-2,3-butanediol dehydrogenase (R,R-BD-DH). A homology search revealed M. gilvum, M. vanbaalenii, and M. semegmatis to have ORFs similar to mbd1, suggesting the widespread distribution of genes encoding R,R-BD-DH among mycobacterial strains.     

Enantioselective disposition of oral amlodipine in healthy volunteers

Plasma concentrations of (R)- and (S)-amlodipine were measured after single oral administrations to 18 healthy volunteers of 20 mg amlodipine racemate. The contribution of the pharmacologically active (S)-enantiomer to the concentrations of total amlodipine (sum of enantiomers) was significantly higher than that of the inactive (R)-enantiomer, with mean values of 47% R to 53% S for the C_max and 41% R to 59% S for the AUC (range between 24% R:76% S and 50% R:50% S). The oral clearance of the active (S)-form was subject to much less intersubject variation (25% CV) than that of the inactive (R)-form (52% CV). (R)-Amlodipine was more rapidly eliminated from plasma than (S)-amlodipine, with mean terminal half-lives of 34.9 h (R) and 49.6 h (S). The terminal half-lives of total amlodipine (mean 44.2 h) were strongly correlated with—and thus highly predictive for—the half-lives of the (S)-enantiomer. It is proposed that the observed enantioselectivity of oral amlodipine is due to differences in the systemic blood clearance of the enantiomers. © 1994 Wiley-Liss, Inc.     

Synthesis and polymerization of benzyl (3R,4R)-3-methylmalolactonate via enzymatic preparation of the chiral precursor

β-methylaspartate ammonia-lyase, EC 4.3.1.2, (β-methylaspartase) from Clostridium tetanomorphum was used to produce a 40/60 molar ratio of (2S,3R) and (2S,3S)-3-methylaspartic acids, 2a and 2b , respectively, from mesaconic acid 1 as substrate, on a large scale. To prepare (3R,4R)-3-methyl-4-(benzyloxycarbonyl)-2-oxetanone (benzyl 3-methylmalolactonate) 6, 2a and 2b were transformed, in the first step, into 2-bromo-3-methylsuccinic acids 3a and 3b and separated. After three further steps, (2S,3S)- 3a yielded the α,β-substituted β-lactone (3R,4R) 6 with a very high diastereoisomeric excess (>95% by chiral gas chromatography). The corresponding crystalline polymer, poly[benzyl β-(2R,3S)-3-methylmalate] 8 , prepared by an anionic ring opening polymerization, was highly isotactic as determined by ¹³C NMR. Catalytic hydrogenolysis of lactone 6 yielded (3R,4R)-3-methyl-4-carboxy-2-oxetanone (3-methylmalolactonic acid) 7 , to which reactive, chiral, or bioactive molecules can be attached through ester bonds leading to polymers with possible therapeutic applications. Because of the ability of β-methylaspartase to catalyse both syn- and anti-elimination of ammonia from (2S,3RS)-3-methylaspartic acid 2ab at different rates, the (2S,3R)-stereoisomer 2a was retained and isolated for further reactions. These results permit the use of the chemoenzymatic route for the preparation of both optically active and racemic polymers of 3-methylmalic acid with well-defined enantiomeric and diastereoisomeric compositions. Chirality 10:727–733, 1998. © 1998 Wiley-Liss, Inc.     

Production of a new terpenoid from biotransformation of (-)-isolongifolanol by Aspergillus niger and suppression of SOS-inducing activity

Abstract

The stereoselective oxidation of (—)-isolongifolanol (1) with a longifolene skeleton by Aspergillus niger (NBRC 4414) as a biocatalyst and suppressive effect on umuC gene expression by chemical mutagens furylfuramid and AFB1 of the SOS response in Salmonella typhimurium TA1535/pSK1002 were investigated. Compound 1 was converted to a new terpenoid, (-)-(2S,8R)-8,12-dihydroxy-isolongifolanol (2). Its structure was determined by NMR, IR, specific rotation and mass spectrometry. The metabolites suppressed the SOS-inducing activity of furylfuramid and AFB₁ in the umu test. Compound 1 suppressed 51% of the SOS-inducing activity against furylfuramid at < 1.0 mM. Compound 2 suppressed 15% and 24% of the SOS-inducing activity against furylfuramid and AFB1 at < 1.0 mM respectively.     

红豆杉一内生真菌化学成分的研究

从药用植物红豆杉(Taxus chinensis (Pilg.) Rehd.)的内生真菌--粘帚霉属真菌(Gliocladium sp., 简称F菌)菌丝体中分离到3个化合物, 根据光谱方法确定了它们的结构.其中,(20S,22S)-4a-同-22-羟基-4-氧杂麦角甾-7, 24 (28)-二烯-3-酮为新化合物,化合物4, 8, 12, 16-四甲基-1, 5, 9, 13-四氧杂环十六烷-2, 6, 10, 14-四酮为首次从该属真菌中分离到, 6,9-环氧麦角甾-7,22-二烯-3-羟基为首次从F菌中分离到.     

A new model to account for the order in which enantiomers of alkylarylcarbinols elute from a Pirkle chiral HPLC column: preparation, absolute stereochemistry, and chromatographic properties of (+)-1,2-benzocyclononen-3-ol and (+)-1,2-benzocyclodecen-3-ol

Samples enriched in (-)- and (+)-1,2-benzocyclononen-3-ol were prepared by microbially mediated reactions. An enriched sample of (+)-1,2-benzocyclodecen-3-ol was prepared by fractional crystallization of the diastereoisomeric camphanates, followed by hydrolysis. The absolute stereochemistry of both alcohols was established by chemical transformations. The elution order of their enantiomers from a chiral Pirkle HPLC column [(R)-N-(3,5-dinitrobenzoyl)phenyl glycine ionically bound to gamma-aminopropyl silanized silica] was determined. The information in conjunction with other data was used to formulate a rule to predict the configuration of an enantiomer of an alkylarylcarbinol from its elution order from this column.     

Synthesis of the Racemate and Both Enantiomers of Massoilactone

A simple and efficient synthesis of (±)-massoilactone (1) as a key substance for the butter and milk flavor was accomplished from n-hexanal in only a few steps. Application of its racemic synthesis enabled natural (R)-(?)- and unnatural (S)-(+)-massoilactone (1a, 1b) to be synthesized by starting from commercially available (R)-(+)-1,2-epoxyheptane (5).     

Production and Characterization of a Pressure-induced Gel from Freeze-concentrated Milk

A process was developed to produce a characteristic milk gel. Raw and market milk samples were freeze-concentrated using bacterial ice nuclei. The concentrates were kept at 5°C and compressed at 300–600 MPa for 5 min. The combination of the freeze concentration and the pressurization gave a milk gel without adding any gelling agents. The addition of sugar at 10% to the concentrated milk improved its gel strength and viscoelasticity. The gel was characterized by a phase transition at about 62–75°C.     

An evaluation of ibuprofen bioinversion by simulation.

Using a pharmacokinetic model recently proposed to explain ibuprofen disposition in man, plasma concentrations of pure ibuprofen enantiomers were simulated following oral administration of (-)-(R)-ibuprofen, (+)-(S)-ibuprofen, or rac-ibuprofen. Simulated and literature values for AUC's were used to compare S/R ratios for different cases of the model and for different methods of calculating the fraction of R bioinverted to S. Numerical simulation using STELLA confirmed previous results for different cases of bioinversion. Simulated S/R AUC ratios, for administration of the racemate, ranged from 4.0 (presystemic bioinversion) to 1.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 1.53 +/- 0.2 for administration of the racemate; therefore, systemic bioinversion was concluded to be representative of ibuprofen disposition. Additional simulations of S/R AUC ratios, for administration of (-)-(R)-ibuprofen only, ranged from 1.5 (presystemic bioinversion) to 0.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 0.50 +/- 0.9 for administration of (-)-(R)-ibuprofen only, which again supported conclusions of systemic bioinversion. Using different equations for estimation of fraction of R inverted to S (FR----S), results based on simulated data were identical; however, FR----S values based on literature data were different. Therefore, assumptions made for different FR----S equations do not appear to be rigorous. Calculations of FR----S, based on literature data, averaged 0.52 overall, indicating bioavailability of (+)-(S)-ibuprofen may be similar for a 150 mg dose of (+)-(S)-ibuprofen compared to a 200 mg dose of racemate.     

A FMRFamide-like peptide is associated with the myotropic ovulation hormone in Rhodnius prolixus.

The protocerebral neurosecretory cells previously shown to be the source of the myotropin controlling ovulation in Rhodnius prolixus react in an immunocytochemical assay using an antiserum against FMRFamide. When the same antiserum was injected into fed mated females at the appropriate time the timing of oviposition was delayed, but the total number of eggs developed was unaffected compared to controls injected with pre-immune rabbit serum. The titer of FMRFamide-like peptide (assayed by RIA) in the hemolymph of mated and virgin females was found to fluctuate with the egg laying cycle, and to reflect earlier determinations of the titer of myotropic activity. Western blots of SDS-PAGE revealed a FMRFamide-immunoreactive peptide of approximately 8.5 kDa in both hemolymph and extracts of the ovulation hormone cells.     

Synthesis of sterols oxygenated in the terminal fragment of their side chains

Methods of stereoselective synthesis of oxysterols are considered by the examples of (25R)-26-hydroxycholesterol, (24S)-24,25-epoxycholesterol, and (24S)-24-hydroxycholesterol containing functional groups in the terminal fragments of their side chain. Special attention is paid to the problems of construction of chiral centers C24 and C25.     

Stereochemistry of Female-Specific Normonoterpenes,Sex Pheromone Candidates from the Acarid Mite,Tyreophagus sp. (Astigmata: Acaridae)

Two normonoterpenes were detected from an unidentified Tyreophagus sp. as new female-specific components. Both planar structures were identified to be 2,6-dimethyl-5-heptenal (1) and 2,6-dimethyl-5-hepten-1-ol (2) by GC/MS co-chromatography with synthetic 1 and 2. The stereochemistry of 2 was determined to be R by a GC analysis with a chiral column, while that of 1 was presumed to be similar to 2 based on the biosynthetic aspects.     

红豆杉一内生真菌化学成分的研究(英文)

从药用植物红豆杉 (Taxuschinensis (Pilg.)Rehd .)的内生真菌———粘帚霉属真菌 (Gliocladiumsp .,简称F菌 )菌丝体中分离到 3个化合物 ,根据光谱方法确定了它们的结构。其中 ,(2 0S ,2 2S)_4a_同_2 2_羟基_4_氧杂麦角甾_7,2 4 (2 8)_二烯_3_酮为新化合物 ,化合物 4 ,8,12 ,16_四甲基_1,5 ,9,13_四氧杂环十六烷_2 ,6 ,10 ,14_四酮为首次从该属真菌中分离到 ,6 ,9_环氧麦角甾_7,2 2_二烯_3_羟基为首次从F菌中分离到。     

Enantiomeric cuparene-type sesquiterpenoids from Bazzania pompeana

Two enantiomeric cuparene-type sesquiterpenoids, (R)-(−)-cuparene (1) and (R)-(−)-δ-cuparenol (2), have been isolated from the liverwort, Bazzania pompeana. The structures and absolute configurations of the two compounds have been determined.     

Kinetics of acetophenone reduction to (R)-1-phenylethanol by a whole-cell Pichia capsulata biocatalyst

(R)-1-phenylethanol is an important substance in fragrance and flavor industry. In this work, the reduction of acetophenone to (R)-1-phenylethanol in an aqueous medium was examined using Pichia capsulata as a whole-cell biocatalyst. Progress curve and initial rate measurements were used to obtain kinetic data. The experiments were carried out at pH 5, temperature of 25?°C, and in the presence of glucose to maintain in vivo regeneration of NADH. A model of the reversible reaction kinetics considering the substrate inhibition of the forward reaction was developed. Five kinetic parameters of this model were determined by a simultaneous fit of a reaction rate dependence on substrate concentration and 18 substrate and product concentration progress curves with very good accuracy. Equilibrium constant of the reaction and equilibrium conversion of acetophenone to (R)-1-phenylethanol were 13.7 and 93%, respectively.     

Purification and Properties of UDP-galactose 4-Epimerase from Bifidobacterium bifidum

UDP-galactose 4-epimerase (EC 5.1.3.2) was purified to a homogeneous state from Bifidobacterium bifidutn grown on a glucose medium. The molecular weight was estimated to be about 90,000. The purified enzyme was very stable and 60 % of its initial activity survived three months of storage at 4°C even at a low protein concentration (0.2 mg/ml). The optimum pH was 9.0, and the Km values for UDP-galactose and UDP-glucose were 5.4 × 10^-4 M and 1.4×10 ^-3 M. UDP was a competitive inhibitor. The enzyme activity was stimulated by various sugar phosphates, but was slightly inhibited by fructose 1,6-diphosphate (FDP). A high concentration of galactose or glucose, which had no effect by itself, inhibited the activity in combination with UMP. The inhibition by FDP was also enhanced by combination with UMP.     

来自普哥滨珊瑚的一株Talaromyces sp.真菌的活性次生代谢产物

利用硅胶柱层析、制备型HPLC和重结晶等手段从普哥滨珊瑚分离的一株Talaromyces sp.真菌C21-1中筛选得到2个活性化合物,运用核磁共振、质谱和圆二色谱等技术鉴定这两个化合物分别为(R)-(-)-hydroxysydonic acid（1）和homodimeric WIN 64821（2）,补充完善了化合物2的核磁共振信号归属,并对化合物进行抗菌活性和乙酰胆碱酯酶抑制活性的测定,发现化合物1对白色假丝酵母Canidia albicans和耐甲氧基青霉素的金黄色葡萄球菌Methicillin-resistant Staphylococcus aureus（MRSA）具有一定的抑制作用,其最低抑菌浓度（MIC）分别为0.075mmol/L和0.2mmol/L,对副溶血弧菌Vibrio parahemolyticus的抑制活性较弱,在0.2mmol/L浓度下的抑制率为17%;化合物2最大浓度0.2mmol/L条件下对这3种菌均没有明显的抑制效果。化合物2表现出剂量依赖的乙酰胆碱酯酶抑制活性,0.5mmol/L时抑制率达到35.1%。