首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
(S)-(−)- and (R)-(+)-limonene was transformed to carvone via corresponding cis- and trans-carveol using Solanum aviculare and Dioscorea deltoidea plant cells. Both carveols and carvone formed were racemic in all biotransformations.  相似文献   

2.
The primary monoterpene accumulated in the glandular trichomes of spearmint (Mentha spicata) is the ketone (−)-carvone which is formed by cyclization of the C10 isoprenoid intermediate geranyl pyrophosphate to the olefin (−)-limonene, hydroxylation to (−)-trans-carveol and subsequent dehydrogenation. Selective extraction of the contents of the glandular trichomes indicated that essentially all of the cyclase and hydroxylase activities resided in these structures, whereas only about 30% of the carveol dehydrogenase was located here with the remainder located in the rest of the leaf. This distribution of carveol dehydrogenase activity was confirmed by histochemical methods. Electrophoretic analysis of the partially purified carveol dehydrogenase from extracts of both the glands and the leaves following gland removal indicated the presence of a unique carveol dehydrogenase species in the glandular trichomes, suggesting that the other dehydrogenase found throughout the leaf probably utilizes carveol only as an adventitious substrate. These results demonstrate that carvone biosynthesis takes place exclusively in the glandular trichomes in which this natural product accumulates.  相似文献   

3.
The aqueous substrate and product toxicity thresholds in the microbial biotransformation of (-)-trans-carveol to the fragrance/flavor compound (R)-(-)-carvone by Rhodococcus erythropolis were determined. Above aqueous phase concentrations of approx. 500 mg carveol/l and 200-600 mg carvone/l, the biotransformation activity of the biocatalyst was inhibited. This biotransformation was undertaken in a single aqueous phase 3 l [corrected] reactor in which a total of 5 ml carveol (mixture of isomers) was added before the biotransformation rate decreased significantly. The carvone volumetric productivity was 31 mg/lh. Although the growth of the organism post-exposure was not affected, dramatic morphological changes in response to the accumulation of the inhibitory substrate and product were observed.  相似文献   

4.
Treatment of 3,5,6-tri-O-benzoyl-- -glucofuranose 1,2-sulfite with an excess of bis(trimethylsil) uracil, in fusion processes without any catalyst, afforded an excellent yield of 1-(3,5,6-tri-O-benzoyl-2-O-trimethylsilyl-β- -glucofuranosyl)uracil, which was readily hydrolyzed in slightly acid conditions to give in almost quantitative yield 1-(3,5,6-tri-O-benzoyl-β- -glucofuranosyl)uracil. This new synthetic method for nucleosides unprotected at O-2′ was also tested in other sugar series. In some cases, only the 1′,2′-trans-nucleosides were obtained, but in others, small yields (3–10%) of 1′,2′-cis-nucleosides were detected. The -to-β ratio seems to be dependent on the reaction temperature. 2,4-Dimethoxypyrimidine also reacted with sugar 1,2-sulfites and 4-O-methyl-1-(3,5,6-tri-O-benzyl-β- -glucopyranosyl)-2-pyrimidinone was prepared in 85% yield from 3,5,6-tri-O-benzyl-- -glucopyranose 1,2-sulfite.  相似文献   

5.
Monoterpene biosynthesis pathway construction in Escherichia coli   总被引:3,自引:0,他引:3  
Four genes encoding sequential steps for the biosynthesis of the spearmint monoterpene ketone (-)-carvone from the C(5) isoprenoid presursors isopentenyl diphosphate and dimethylallyl diphosphate were installed in Escherichia coli. Inducible overexpression of these genes in the bacterial host allowed production of nearly 5 mg/l of the pathway intermediate (-)-limonene, which was mostly excreted to the medium such that products of the downstream steps, (-)-carveol and (-)-carvone, were not detected. Assay of pathway enzymes and intermediates indicated that flux through the initial steps catalyzed by geranyl diphosphate synthase and limonene synthase was severely limited by the availability of C(5) isoprenoid precursors in the host. Feeding studies with (-)-limonene, to overcome the flux deficiency, demonstrated the functional capability of limonene-6-hydroxylase and carveol dehydrogenase to produce the end-product carvone; however, uptake and trafficking restrictions greatly compromised the efficiency of these conversions.  相似文献   

6.
Four monoterpenoids, (−)- and (+)-menthols, terpinolene and carvotanacetone were biotransformed by Aspergillus niger and several related species. Aspergillus niger converted (−)-menthol to 1-, 2-, 6-, 7-, and 9-hydroxymenthols and the mosquito repellent-active 8-hydroxymenthol. On the other hand, (+)-menthol was smoothly biotransformed by A. niger to give 7-hydroxymenthol. Aspergillus cellulosae biotransformed (−)-menthol specifically to 4-hydroxymenthol. Terpinolene and (−)-carvotanacetone were converted by A. niger to two , β-unsaturated ketones, a fenchane-type compound and diastereoisomeric p-menthane-2,9-diols and 8-hydroxycarvomenthol, respectively.  相似文献   

7.
Leaves of Virola pavonis yielded a (7,7′β,8β,8′)-4,4′-dihydroxy-3,3′5,5′-tetramethoxy-7,7′-epoxyligna (−)-di-de-O-methylgrandisin.  相似文献   

8.
The optimization of a continuous enzymatic reaction yielding (R)-(−)-phenylacetylcarbinol ((R)-PAC), a key intermediate of the (1R,2S)-(−)-ephedrine synthesis, is presented. We compare the suitability of different mutants of the pyruvate decarboxylase (PDC) from Zymomonas mobilis with respect to their application in biotransformation using pyruvate or acetaldehyde and benzaldehyde as substrates, respectively. Starting from 90 mM pyruvate and 30 mM benzaldehyde, (R)-PAC was obtained with a space time yield of 27.4 g/(L·day) using purified PDCW392I in an enzyme-membrane reactor. Due to the high stability of the mutant enzymes PDCW392I and PDCW392M towards acetaldehyde, a continuous procedure using acetaldehyde instead of pyruvate was developed. The kinetic results of the enzymatic synthesis starting from acetaldehyde and benzaldehyde demonstrate that the carboligation to (R)-PAC is most efficiently performed using a continuous reaction system and feeding both aldehydes in equimolar concentration. Starting from an inlet concentration of 50 mM of both aldehydes, (R)-PAC was obtained with a space-time yield of 81 g/(L·day) using the mutant enzyme PDCW392M. The new reaction strategy allows the enzymatic synthesis of (R)-PAC from cheap substrates free of unwanted by-products with potent mutants of PDC from Z. mobilis in an aqueous reaction system.  相似文献   

9.
A stereospecific high-performance liquid chromatography method for the determination of trans-(−)-paroxetine and its enantiomer in bulk raw material and pharmaceutical formulations was developed and validated. The enantiomeric separation was achieved, without any derivatization, on a carbamate derivative-based column (Chiralpak AD). The effect of the organic modifiers, 2-propanol and ethanol, in the mobile phases was optimised to obtain enantiomeric separation. Limits of detection and quantitation of 2 and 6 ng, respectively, were obtained for both of the enantiomers. The linearity was established in the range of 5–41 μg for trans-(−)-paroxetine and in the range of 10–160 ng for trans-(+)-paroxetine. The accuracy of the method was 102.3% (mean value) for trans-(−)-paroxetine and 99.9% (mean value) for trans-(+)-paroxetine. For the precision (repeatability), a relative standard deviation value of 1.5% (mean value) for trans-(−)-paroxetine and of 2.1% (mean value) for trans-(+)-paroxetine was found. The method is capable of determining a minimum limit of 0.2% of trans-(+)-isomer in commercial samples.  相似文献   

10.
The phosphinoalkenes Ph2P(CH2)nCH=CH2 (n= 1, 2, 3) and phosphinoalkynes Ph2P(CH2)n C≡CR (R = H, N = 2, 3; R = CH3, N = 1) have been prepared and reacted with the dirhodium complex (η−C5H5)2Rh2(μ−CO) (μ−η2−CF3C2CF3). Six new complexes of the type (ν−C5H5)2(Rh2(CO) (μ−η11−CF3C2CF3)L, where L is a P-coordinated phosphinoalkene, or phosphinoalkyne have been isolated and fully characterized; the carbonyl and phosphine ligands are predominantly trans on the Rh---Rh bond, but there is spectroscopic evidence that a small amount of the cis-isomer is formed also. Treatment of the dirhodium-phosphinoalkene complexes with (η−CH3C5H4)Mn(CO)2thf resulted in coordination of the manganese to the alkene function. The Rh2---Mn complex [(η−C5H5)2Rh2(CO) (μ−η11−CF3C2CF3) {Ph2P(CH2)3CH=CH2} (η−CH3C5H4)Mn(CO)2] was fully characterized. Simi treatment of the dirhodium-phosphinoalkyne complexes with Co2(CO)8 resulted in the coordination of Co2(CO)6 to the alkyne function. The Rh2---Co2 complex [(η−C5H5)2Rh2(CO) (μ−η11−CF3C2CF3) {Ph2PCH2C≡CCH3}Co2(CO)2], C37H25Co2F6O7PRh2, was fully characteriz spectroscopically, and the molecular structure of this complex was determined by a single crystal X-ray diffraction study. It is triclinic, space group (Ci1, No. 2) with a = 18.454(6), B = 11.418(3), C = 10.124(3) Å, = 112.16(2), β = 102.34(3), γ = 91.62(3)°, Z = 2. Conventional R on |F| was 0.052 fo observed (I > 3σ(I)) reflections. The Rh2 and Co2 parts of the molecule are distinct, the carbonyl and phosphine are mutually trans on the Rh---Rh bond, and the orientations of the alkynes are parallel for Rh2 and perpendicular for Co2. Attempts to induce Rh2Co2 cluster formation were unsuccessful.  相似文献   

11.
The effect of eye carotenoid content, light conditions and retinoid supply on the biosynthesis of opsin, as well as the ability to isomerize of exogenous all-trans-retinal to 11-cis-retinal were investigated in the photoreceptors of blowfly Calliphora. SDS-PAGE of digitonin extracts from isolated rhabdom fractions of carotenoid-fortified and carotenoid-deficient animals revealed, on heavily loaded gels, that in both cases opsin forms faint minor bands similar to the patterns of “R-flies” described as “vitamin A-deficient flies” (Paulsen and Schwemer, Biochim. biophys Acta 557, 358–390, 1979) or “carotenoid-deficient flies” (Paulsen and Schwemer, Eur. J. Biochem. 137, 609–614, 1983. Similar opsin patterns were obtained in flies subjected to continuous 72 h blue or yellow-green light or to a 12 h: 12 h white light:dark cycle, or total darkness, irrespective of the carotenoid content in their eyes. 11-cis-retinal and, to a lesser extent, all-trans-retinal, when included in the diet or painted on the cornea, were found to stimulate opsin biosynthesis in the dark. 11-cis-retinal in the dark or all-trans-retinal after illumination of the flies with blue light were the most effective, as compared with the effect of all-trans-retinal in the dark. Exogenous all-trans-retinal in the dark can be partially converted into a mixture of 11-cis-retinal (26%) and 13-cis-retinal (74%) by fly retina homogenate in vitro. It was concluded that Calliphora opsin biosynthesis is not strongly dependent on the carotenoid supply or on light: dark conditions and is triggered by the 11-cis aldehyde form of the chromophore, which can be produced in the fly retina either by an isomerase system in the dark or as a result of photoisomerization.  相似文献   

12.
Anne Joliot 《BBA》1974,357(3):439-448
The fluorescence yield has been measured on spinach chloroplasts at low temperature (−30 to −60°C) for various dark times following a short saturating flash. A decrease in the fluorescence yield linked to the reoxidation of the Photosystem II electron acceptor Q is still observed at −60°C. Two reactions participate in this reoxidation: a back reaction or charge recombination and the transfer of an electron from Q to Pool A. The relative competition between these two reactions at low temperature depends upon the oxidation state of the donor side of the Photosystem II center:

1. (1) In dark-adapted chloroplasts (i.e. in States S0+S1 according to Kok, B., Forbush, B. and McGloin, M. (1970) Photochem. Photobiol. 11, 457–475), Q, reduced by a flash at low temperature, is reoxidized by a secondary acceptor and the positive charge is stabilized on the Photosystem II donor Z. Although this reaction is strongly temperature dependent, it still occurs very slowly at −60°C.

2. (2) When chloroplasts are placed in the S2+S3 states by a two-flash preillumination at room temperature, the reoxidation of Q after a flash at low temperature is mainly due to a temperature-independent back reaction which occurs with non-exponential kinetics.

3. (3) Long continuous illumination of a frozen sample at −30°C causes 6–7 reducing equivalents to be transferred to the pool. Thus, a sufficient number of oxidizing equivalents should have been generated to produce at least one O2 molecule.

4. (4) A study of the back reaction in the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) shows the superposition of two distinct non-exponential reactions one temperature dependent, the other temperature independent.

Abbreviations: DCMU; 3(3; 4-dichlorophenyl)-1; 1-dimethylurea  相似文献   


13.
The activity and enantioselectivity of Candida rugosa lipase were investigated in chiral solvents, (–)-, (+)- and racemic carvone, for the resolution of 2-chloro-propionic acid with n-butanol via esterification. The activity of the enzyme studied was about 50% higher in (–)-carvone than in (+)-carvone, however the enantioselectivity was similar.  相似文献   

14.
A useful preparative route to nitrogen-containing, carbocyclic derivatives is described from (−)-quinic acid. (−)-Quinic acid was converted via the 3,4-O-cyclohexylidene-lactone into 1- -3-O-tosyl-5-C-tosyloxymethylcyclohexane-1,2,5/3-tetrol (5) by sequential reduction with sodium borohydride, toluene-p-sulphonylation, and acid hydrolysis. Reaction of the disulphonate 5 with methanolic sodium methoxide afforded 1- -1,2:5,7-dianhydro-5-C-hydroxymethylcyclohexane-1,2,3,5/0-tetrol (6). The ring-opening reactions of the diepoxide 6 with azide ion furnished a mixture of two diazides 9 and 13 in the ratio 4 to 1. The structure and conformation of the derived dibenzoates 10 and 14 have been determined by n.m.r. spectroscopy.  相似文献   

15.
Complexes of type A4[VO(tart)]2·nH2O, where A = Rb or Cs and tart =d,l-tartrate(4−) (n = 2) or d,d-tartrate(4−) (n = 2 for Rb and n = 3 for Cs), were prepared from an aqueous mixture of V2O5, AOH and H4tart. These complexes were studied by single-crystal X-ray diffraction methods: Rb4[VO(d,l-tart)]2·2H2O, space group P1 with a = 8.156(1),b = 8.246(1),c = 8.719(1)Å, = 66.09(1)°, β = 65.07(1)°, γ = 82.40(1)°,Z = 2, 1917 observed reflections, and final Rw = 0.035; Cs4[VO(d,l-tart)]2·2H2O, space group P21/c with a = 9.350(1),b = 13.728(2),c = 8.479(1)Å, β = 106.77(1)°,Z = 4, 2235 observed reflections, and final Rw = 0.054; Rb4[VO(d,d-tart)]2·2H2O, space group P4122 with a = 8.072(1),c = 32.006(3)Å,Z = 8, 1014 observed reflections and final Rw = 0.038; Cs4[VO(d,d-tart)]2·3H2O, space group P122 with a = 8.184(1),c = 33.680(5)Å,Z = 8, 1310 observed reflections, and final Rw = 0.063. Bulk magnetic susceptibility data (1.5–300 K) for these compounds and A4[VOl,l-tart)]2·nH2O (A = Rb, Cs) were obtained on polycrystalline samples. These data were analyzed in terms of a Van Vleck exchange coupled S = 1/2 model which was modified to include an interdimer exchange parameters Θ. Analysis of the low-temperature (1.5–20 K) susceptibility data gave 2J = +1.30 cm−1 and Θ = −1.86 K for Rb4[VO(d,l-tart)]2·2H2O, 2J = +1.16 cm−1 and Θ = −1.69 K for Cs4[VO(d,l-tart)]2·2H2O, 2J = +1.90 cm−1 and Θ = −0.82 K for Rb4[VO(d,d-tart)]2·2H2O, 2J = +2.04 cm−1 and Θ = −0.80 K for Rb4[VO(l,l-tart)]2·2H2O, 2J = +1.52 cm−1 and Θ = −0.25 K for Cs4[VO(d,d-tart)]2·3H2O, and 2J = +1.64 cm−1 and Θ = −0.31 K for Cs4[VO(l,l-tart)]2·3H2O. These results suggest the magnitudes of intradimer (ferromagnetic and interdimer (antiferromagnetic) exchange interactions are similar in these complexes, as observed for the analogous Na salts.  相似文献   

16.
Oxygenation of [CuII(fla)(idpa)]ClO4 (fla=flavonolate; IDPA=3,3′-iminobis(N,N-dimethylpropylamine)) in dimethylformamide gives [CuII(idpa)(O-bs)]ClO4 (O-bs=O-benzoylsalicylate) and CO. The oxygenolysis of [CuII(fla)(idpa)]ClO4 in DMF was followed by electronic spectroscopy and the rate law −d[{CuII(fla)(idpa)}ClO4]/dt=kobs[{CuII(fla)(idpa)}ClO4][O2] was obtained. The rate constant, activation enthalpy and entropy at 373 K are kobs=6.13±0.16×10−3 M−1 s−1, ΔH=64±5 kJ mol−1, ΔS=−120±13 J mol−1 K−1, respectively. The reaction fits a Hammett linear free energy relationship and a higher electron density on copper gives faster oxygenation rates. The complex [CuII(fla)(idpa)]ClO4 has also been found to be a selective catalyst for the oxygenation of flavonol to the corresponding O-benzoylsalicylic acid and CO. The kinetics of the oxygenolysis in DMF was followed by electronic spectroscopy and the following rate law was obtained: −d[flaH]/dt=kobs[{CuII(fla)(idpa)}ClO4][O2]. The rate constant, activation enthalpy and entropy at 403 K are kobs=4.22±0.15×10−2 M−1 s−1, ΔH=71±6 kJ mol−1, ΔS=−97±15 J mol−1 K−1, respectively.  相似文献   

17.
Carvone has previously been found to highly inhibit its own production at concentrations above 50 mM during conversion of a diastereomeric mixture of (−)-carveol by whole cells of Rhodococcus erythropolis. Adaptation of the cells to the presence of increasing concentrations of carveol and carvone in n-dodecane prior to biotransformation proved successful in overcoming carvone inhibition. By adapting R. erythropolis cells for 197 h, an 8.3-fold increase in carvone production rate compared to non-adapted cells was achieved in an air-driven column reactor. After an incubation period of 268 h, a final carvone concentration of 1.03 M could be attained, together with high productivity [0.19 mg carvone h−1 (ml organic phase)−1] and high yield (0.96 g carvone g carveol−1).  相似文献   

18.
Measurements of chromosomal DNA fiber replication of cells of cultured pea root meristems in early S via autoradiography showed a 3-fold increase in rate of fork movement in the first 2 h. The initial rate was 4.5–6 μm h−1 but forks active after 90 min moved at nearly 18 μm h−1. The faster movement was not characteristic of all replicons. Certain fibers consisted of replicons of a smaller mean size (38–42 μm) with slowly moving forks (4.5–6 μm h−1 fork−1) and others had replicons almost 50 μm long with forks that moved more rapidly.  相似文献   

19.
1,25(OH)2D3 and two stereoisomers of retinoic acid, all trans and 9-cis retinoic acid, are regulators of cell proliferation and differentiation. The aim of this study was to evaluate the effects of a combination of 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) on proliferation and cell differentiation of the human promyelocytic leukemia cell line HL60, and to test the reversibility of the induced differentiation. Cell proliferation was inhibited as expected by 1,25(OH)2D3 and all trans retinoic acid alone (IC50 of cell survival was 4 × 10−7 M, 9 × 10−6 M and 9 × 10−7 M for 1,25(OH)2D3, all trans and 9-cis retinoic acid, respectively). Combination of 1,25(OH)2D3 and either form of retinoic acid resulted in a partially additive decrease in cell proliferation. 1,25(OH)2D3 induced a monocytic differentiation (100% CD14+ cells with 10−7 M 1,25(OH)2D3), while retinoic acid led to a predominantly granulocytic differentiation (36 and 42% CD67+ cells with 10−6 M all trans and 9-cis retinoic acid, respectively). Additive effects on differentiation were observed upon combination of subtherapeutical doses of the drugs, achieving a mainly monocytic population, demonstrating the dominant role of 1,25(OH)2D3 in determining the direction of differentiation. The effects on proliferation and differentiation of the solitary drugs were reversible, while the proliferation arrest and differentiation induced by the combination persisted and even progressed after withdrawal of the drugs. We conclude that 1,25(OH)2D3 and retinoic acid (all trans or 9-cis) exert additive effects on inhibition of proliferation and induction of cell differentiation of HL60 cells, leading to a persistent differentiation, even after drug withdrawal.  相似文献   

20.
To date, plantlet culture has not been explored as a means to obtain secondary metabolites in vitro. However, plantlets readily produce desirable secondary metabolites, which may not be produced in cell suspension or callus cultures. To optimize plantlet growth in vitro, the influences of various physical environments on the growth (fresh weight), morphogenesis (leaf, root, and shoot number), and volatile carbon metabolites (i.e. monoterpene, (−)-carvone) of Mentha spicata L. (spearmint) plants were studied. The carvone content in different portions of sterile plantlets was analyzed. Carvone was only produced from the foliar regions of cultured plantlets and was absent in the callus and roots. The influence of physical support (e.g., agar, glass gravel, liquid, platform or sponge), frequency of media replacement, and culture vessel capacity on spearmint plantlets growth and carvone production was tested. A comparative study was conducted testing the growth, morphogenesis, and secondary metabolism occurring with three different spearmint cultivars grown in either culture tubes containing 25 ml agar medium or in an automated plant culture system (APCS; a sterile hydroponics system) employing a 1-l medium reservoir. Increasing the number of media immersions (4, 8, 12 or 16 immersions d−1) of plantlets growing in the APCS increased growth and morphogenesis responses. Generally, higher culture growth rates resulted in lower carvone treatment−1 (mg carvone g-FW−1); however, overall total carvone ((mg carvone g-FW−1) × g culture FW) increased because of the production of greater biomass obtained per vessel.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号