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1.
The sterol fraction from the marine worm Linneus torquatus Coe (phylum Nemertini, class Anopla, family Lineidae) has been isolated, separated by HPLC and preparative TLC on AgNO 3-impregnated silica gel, and sterols identified using GC, GC-MS and NMR spectroscopy. It was shown that the fraction contains at least 12 sterols belonging mainly to Δ 5,22, Δ 5,24(28) and Δ 5 series. The major sterol components were 24-methylcholesta-5,24(28)-dien-3β-ol, cholesta-5,22E-dien-3β-ol, 24-nor-cholesta-5,22-dien-3β-ol and cholesterol. 相似文献
2.
From the cyclohexane extract of the leaves of Murraya exotica, five novel phytosterols: (23 S)-23-ethyl-24-methyl-cycloart-24(24 1)-en-3β-ol; 3β-methoxy-(23 S)-23-ethyl-24-methyl-cycloart-24(24 1)-en-3β-ol; (23 S)-23-ethyl-24-methyl-cycloart-24(24 1)-3β-yl acetate; (23ξ)-23-isopropyl-24-methyl-cycloart-25-en-3β-ol and (23ξ)-23-isopropyl-24-methyl-cycloart-25-en-3β-yl acetate have been isolated. Structural elucidation of the isolated compounds is based on physical, chemical and spectral analysis including IR, 1H and 13CNMR and mass spectrometry. 相似文献
3.
Steroidal allenes, stigmasta-5,24(28),28-trien-3β-ol (allene-I) and cholesta-5,23,24-trien-3β-ol (allene-II), were tested for their inhibitory effects on growth, development, and steroid metabolism in the silkworm, Bombyx mori. The allenic analogue (I) of stigmasta-5,24(28)-dien-3β-ol (2) was found to be a specific inhibitor for the conversion of stigmast-5-en-3β-ol (1) to stigmasta-5, 24(28)-dien-3β-ol (2) and/or stigmasta-5,24(28)-dien-3β-ol (2) to 24,28-epoxy-stigmast-5-en-3β-ol (3) This inhibitor held the larvae in the second instar for more than 20 days without developing to the third instar, when administered alone or with the dietary sterols of stigmast-5-en-3β-ol (1) or stigmasta-5,24(28)-dien-3β-ol (2). The second allene (II) with a similar structure to cholesta-5,24-dien-3β-ol (4) was also found to be an inhibitor for insect growth and development, but it appeared not to be acting via inhibition of sterol dealkylation. 相似文献
4.
Kinetic results are reported for intramolecular PPh 3 substitution reactions of Mo(CO) 2(η 1-L)(PPh 3) 2(SO 2) to form Mo(CO) 2(η 2-L)(PPh 3)(SO 2) (L = DMPE = (Me) 2PC 2H 4P(Me) 2 and dppe=Ph 2PC 2H 4PPh 2) in THF solvent, and for intermolecular SO 2 substitutions in Mo(CO) 3(η 2-L)(η 2-SO 2) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH 2Cl 2 solvent. Activation parameters for intramolecular PPh 3 substitution reactions: Δ H≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; Δ S≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO 2 in MO(CO) 3(η 2-L)(η 2-SO 2) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO 2 to accept a pair of electrons from the metal, with its bonding transformations of η 2-SO 2 to η 1-pyramidal SO 2, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO) 2(dmpe)(PPh 3)(SO 2) was determined crystallographically: P2 1/ c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) Å 3, Z=4, R( F)=3.49%. 相似文献
5.
The examination of macrophyte, water and sediment samples, collected at depths less than 1.5 m from 50 different sites along the North Aegean coasts, has revealed, for the first time in Greek coastal waters, the presence of two Ostreopsis species ( O. ovata and O. cf. siamensis) and Coolia monotis in the majority of the sampling sites (94% and 100%, respectively). Other epiphytic dinoflagellates of the genera Prorocentrum and Amphidinium and diatoms were accompanying species in this epiphytic community. Morphometric features, plate formula and thecal ornamentation were used for species identification. O. ovata cells were smaller in dorsoventral (DV) diameter and width ( W) (26.18–61.88 μm and 13.09–47.60 μm, respectively) in comparison with O. cf. siamensis (35.70–65.45 μm and 23.80–49.98 μm, respectively). In contrast, the anterioposterior (AP) diameter of O. cf. siamensis was smaller (14.28–26.18 μm) resulting in DV/AP ≈ 3, whereas the above ratio for O. ovata was less than 2 (AP ranging between 14.28–35.70 μm). Moreover, the theca of O. ovata cells was ornamented with scattered pores, which fluctuated in a wider range (0.07–0.32 μm) than those of O. cf. siamensis (0.23–0.29 μm). Coolia monotis cells were almost round with average DV diameter 26.88 μm, AP 25.66 μm and width 26.76 μm. Small and large cells were recorded in both field and culture populations of Ostreopsis spp. and C. monotis, while hyaline cysts were observed for O. ovata. The presence of O. ovata and O. cf. siamensis exhibited a clear seasonal pattern dominating (maximum abundance up to 4.05 × 10 5 cells gr −1 fwm) the period from midsummer to late autumn in years 2003 and 2004, while C. monotis was found also in winter and spring months. 相似文献
6.
The effect of long-term in vivo estrogen treatment on in vitro steroidogenesis by the testes of a young man was investigated. In vitro incubation of testicular tissue of this man with 3H-pregnenolone, 3H-progesterone, 3H-androstenedione and 3H-testosterone demonstrated suppression of 17-hydroxylase activity, with little or no effect of the treatment on Δ 5-3 β-hydroxysteroid oxidoreductase, 5 a-reductase and aromatase. Increased 20 -hydroxysteroid oxidoreductase activity was observed. Determination of intratesticular steroid concentrations led to similar conclusions. 相似文献
7.
Previous in vitro experiments showed that both, Taenia crassiceps and Taenia solium cysticerci have the ability to metabolize exogenous androstenedione to testosterone. Here we evaluate on the capacity of both cysticerci to synthesize several sex steroid hormones, using different hormonal precursors. Experiments using thin layer chromatography (TLC) showed that both cysticerci were able to produce 3H-hydroxyprogesterone, 3H-androstenedione and 3H-testosterone when 3H-progesterone was used as the precursor. They also synthesized 3H-androstenediol and 3H-testosterone when 3H-dehydroepiandrosterone was the precursor. In addition, both cysticerci interconverted 3H-estradiol and 3H-estrone. These results, strongly suggest the presence and activity of the Δ4 and Δ5 steroid pathway enzymes, 3β-hydroxysteroid dehydrogenase/Δ 5-4 isomerase-like enzyme (3β-HSD), that converts androstenediol into testosterone; and the 17β-hydroxysteroid dehydrogenase that interconverts estradiol and estrone, in both types of cysticerci. 相似文献
8.
1. 1. By varying the redox potential of a chloroplast suspension, we obtained new evidence for an equilibrium between states S0 and S1 in the model of Kok, B., Forbush, B. and McGloin, N. (1970, Photochem. Photobiol. 11, 457–475). The mid-point potential of the S0 to S1 couple is close to that for the pool of the electron acceptor of System II, A to A−. 2. 2. The limiting steps between two consecutive photoreactions of System II in Chlorella and spinach chloroplasts, have been studied. 2.1. (a) The limiting step from S1 to S2 (noted γ1 (Δt)) is not exponential. Its temperature coefficient becomes greater as the reaction proceeds. The shape of the kinetics is an intrinsic property of each center. Chloroplasts fixed with 2% glutaraldehyde, show simple first order kinetics. 2.2. (b) The limiting step from S0 to S1 (γ0 (Δt)) exhibits the same characteristics as γ1 (Δt)). 2.3. (c) The limiting step from S2 to S3 (γ2 (Δt)) shows sigmoidal kinetics; two reactions are involved. One of the reactions exhibits the same properties as γ0 (Δt) and γ1 (Δt). 2.4. (d) The limiting step from S3 to S0 (γ3 (Δt)) is a first order reaction, two times slower than the other transitions. This reaction is interpretated in terms of oxygen release.
3. 3. We also studied the limiting steps in the presence of low concentrations (50 μM) of hydroxylamine. The results favor the binding of two molecules of hydroxylamine to every photochemical center.
Abbreviations: DCIP, dichlorophenolindophenol 相似文献
9.
Bark, wood and leaves of Ocotea catharinensis contain respectively 10 (average yield 0.7%.), 15 (average yield 0.004%.) and one (yield 0.4%.) neolignans of the bicyclo[3.2.1]octanoid and the hydrobenzofuranoid structural types, including the new rel-(7 S,8 R,1′ R,4′ S,5′ R,6′ R)-Δ 8′-4′,6′-dihydroxy-5′-methoxy-3,4-methylenedioxy-3′-oxo-8.1′,7.5′-neolignan, (7 S,8 S)-Δ 1′,3′,5′,8′-5,3′,5′-trimethoxy-3,4-methylenedioxy-8.1′,7.O.6′,4.O.7′-neolignan, (7 R,8 S,1′ R,3′ R)-Δ 5′,8′-3,4,3′,5′-tetramethoxy-4′-oxo-8.1′,7.O.6′-neolignan and rel-(7 R,8 S,1′ R,2′ S)-Δ 4′,8′-2′-hydroxy-3,4-dimethoxy-3′-oxo-8.1′,7.O.2′-neolignan. 相似文献
10.
The methanothermal reactions of M(CO) 6 (M = Mo, W) with Na 2S 2 gave a series of homonuclear clusters [{M(CO) 4} n(MS 4)] 2− (M=Mo, W; N=1, 2), i.e. (Ph 4P) 2[(CO) 4Mo(MoS 4)] (I), (Ph 4P) 2[(CO) 4W(WS 4)] (II), (Ph 4P) 2[(CO) 4Mo(MoS 4)Mo(CO) 4] (III) and (Ph 4P) 2[(CO) 4W(WS 4)W(CO) 4] (IV). The two dimers, I and II, as well as the two trimers, III and IV, are isostructural to each other, respectively. All compounds crystallize in the triclinic space group
with Z=2. The cell dimensions are: a=12.393(8), b=19.303(9), c=11.909(6) Å, =102.39(5), β=111.54(5), γ=73.61(5)°, V=2522(3) Å 3 at T=23 °C for I; a=12.390(3), b=19.314(4), c=11.866(2) Å, =102.66(2), β=111.49(1), γ=73.40(2)°, V=2511(1) Å 3 at T=23 °C for II; a=11.416(3), b=22.524(4), c=10.815(4) Å, =91.03(2), β=100.57(3), γ=88.96(2)°, V=2733(1) Å 3 at T=−100 °C for III, a=11.498(1), b=22.600(4), c=10.864(3) Å, =90.92(2), β=100.85(1), γ=88.58(1)°, V=2771(2) Å 3 at T=23 °C for IV. The dimers are each formed by the coordination of the tetrathiometalate as a bidentate chelating ligand to an M(CO) 4 fragment while addition of another M(CO) 4 fragment to the dimers results in the trimers. All compounds contain both tetrahedral and octahedral metal centers with the formal 6+ and 0 oxidation states, respectively. 相似文献
11.
Tricarbonyl-η 5-2,4-dimethyl-2,4-pentadien-1-yl-manganese (1) forms upon UV irradiation in THF at 208 K solvent stabilized dicarbonyl-η 5-2,4-dimethyl-2,4-pentadien-1-yl-tetrahydrofurane-manganese (2). With butynedioic acid dimethyl ester (3) and diphenylacetylene (5) complex 2 yields tricarbonyl-η 5-1,2-dimethoxycarbonyl-4,6-dimethyl- cyclohepta-2,4-dien-1-yl-manganese (4) and tricarbonyl-η-4,6-dimethyl-1,2-diphenyl-cyclohepta-2,4-dien-1-yl- manganese (6) in a formal [5+2] cycloaddition. Addition of carbon monoxide and a 1,4-H shift completes the reaction. Propynoic acid methyl ester (7) forms the 2:1 adduct dicarbonyl-η 5:2-1,3-dimethyl-6-methoxycarbonyl-6- ( E-2′-methoxycarbonylvinyl)-cyclohepta-2,4-dien-1-yl-manganese (8). The crystal and molecular structure of 8 was determined by X-ray structure analysis. The molecular structures of the complexes 4 and 6 were established by IR and NMR spectroscopy. Formation mechanisms of 4, 6 and 8 are discussed. Crystal data for 8: monoclinic space group P2 1/ c, a=802.6(3), b=1136.6(1), c=8872.3(3) pm, β=93.14(2)°, V=1.705 nm 3, Z=4. 相似文献
12.
A detailed record (≈2-kyr intervals) of the difference in stable carbon isotopes (Δδ 13C) between Globigerina bulloides and Globigerinoides ruber (pink) is used to reconstruct changes in upwelling intensity off the Congo River for the last 190,000 yr. Comparisons of the oxygen and carbon isotope data from this core with records from the Niger Fan and from pelagic cores in the eastern equatorial South Atlantic indicate that the Congo Fan isotope records do not contain a strong freshwater signal as is described off other major rivers. The temporal pattern of the Δδ 13C signal correlates with the marine organic carbon record from the Congo Fan. Thus the planktonic Δδ 13C record, reflecting past changes in upwelling intensity and nutrient content, corroborates the signal provided by sedimentary organic carbon, which is presumed to indicate changes in the amount of biological productivity and export flux to the seafloor. The planktonic Δδ13C signal is characterized by a dominant 23-kyr periodicity which provides evidence for a strong response of upwelling fluctuations off the Congo to precessional forcing. Minima in the Δδ13C record are aligned with periods of minimum boreal summer insolation over Central Africa reflecting an increase of upwelling and biological productivity off the Congo at periods of enhanced zonal intensity of southeast trades and corresponding weak southeast monsoon over the eastern South Atlantic. A strong response to changes in river discharge probably did not occur, indicating that fertilization by river-derived nutrients has played only a minor role with respect to Late Quaternary changes in the total amount of primary productivity off the Congo. 相似文献
13.
The chemical examination of Acnistus breviflorus afforded nine withanolides, four of which are new and were established as 2,3,24,25-tetrahydro-27-desoxywithaferin A (4β-hydroxy-5β,6β-epoxy-1-oxo-22 R-withanolide), 2,3-dihydro-27-desoxywithaferin A (4β-hydroxy-5β,6β-epoxy-22 R-witha-24-enolide), 5,6-desoxywithaferin A (4β,27-dihydroxy-1-oxo-22 R-witha-2,5,24-trienolide) and 2,3-dihydro-5,6-desoxywithaferin A (4β,27-dihydroxy-1-oxo-22 R-witha-5,24-dienolide). The five known compounds were: withaferin A; 2,3-dihydrowithaferin A; 24,25-dihydro-27-desoxywithaferin A and withaferin A-6,5β-chlorohydrin. 相似文献
14.
Carbon isotope ratios ( 13C/ 12C) were measured for the leaves of the seagrass Thalassia testudinum Banks ex König and carbonates of shells collected at the seagrass beds from seven sites along the coast of southern Florida, U.S.A. The δ 13C values of seagrass leaves ranged from −7.3 to −16.3‰ among different study sites, with a significantly lower mean value for seagrass leaves from those sites near mangrove forests (−12.8 ± 1.1‰) than those far from mangrove forests (−8.3 ± 0.9‰; P < 0.05). Furthermore, seagrass leaves from a shallow water area had significantly lower δ 13C values than those found in a deep water area ( P < 0.01). There was no significant variation in δ 13C values between young and mature leaves ( P = 0.59) or between the tip and base of a leaf blade ( P = 0.46). Carbonates of shells also showed a significantly lower mean δ 13C value in the mangrove areas (−2.3 ± 0.6‰) than in the non-mangrove areas (0.6 ± 0.3‰; P <0.025). In addition, the δ 13C values of seagrass leaves were significantly correlated with those of shell carbonates (δ 13C seagrass leaf = −9.1 + 1.3δ 13C shell carbonate ( R2 = 0.83, P < 0.01)). These results indicated that the input of carbon dioxide from the mineralization of mangrove detritus caused the variation in carbon isotope ratios of seagrass leaves among different sites in this study. 相似文献
15.
[Ru II(Me 2edda)(H 2O) 2] (1), Me 2edda 2− = N, N′-dimethylethylenediaminediacetate, exhibits a sterically-controlled molecular recognition in forming η 2 and η 4 olefin complexes. 1 exists with an N 2O 2 in-plane set of chelate donors and axial H 2O ligands. The two CH 3 functionalities of Me 2edda 2− are poised above and below the N 2O 2 plane of the glycinato rings. Studies herein of the 2,2′-bipyridine complex, [Ru II(Me 2edda)(bpy)], with bidentate bpy chelation as established via 1H NMR and electrochemical methods show 1 to be ligated in the S,S configuration with the glycinato rings in-plane as a cis-O form. 1 is sterically discriminating in forming η 2 complexes with smaller olefins (ethylene, 2-propene, cis-2-butene, methyl vinyl ketone and 3-cyclohexene-1-methanol), but rejects larger decorated ring structures and branched olefins (1,2-dimethyluracil, cyclohexene-1-one 2-methyl-2-propene). η 2 complexes of 1 have characteristic Ru II/III DPP waves near 0.55 V which vary slightly with olefin structure. Potentially bidendate dienes (1,3-butadiene, 1,3-cyclohexadiene and 2,5-norbornadiene (nbd) form η 4 complexes as shown by Ru II/III waves between 0.94 and 1.30 V, indicate of a highly stabilized Ru II center by π-backboning. An η 2η 4 ‘equilibrium’ with apparent K = 22 at 25 °C is observed for nbd coordinated to 1. (The η 2 and η 4 distribution may be a kinetic one and not a thermodynamic one). To allow formation of the cis η 4 complexes, 1 must undergo a shift of one or both glycinato donors from the N 2O 2 plane into the axial site away from the dimethyl functionalities. η 4 chelation by 1,3-butadiene has been confirmed by 1H NMR spectral assignments of two [Ru II(Me 2edda)] isomers, one in the axial rans-O glycinato configuration, e.g. 1,3-butadiene is bidentate in the original N 2O 2 plane and a second unsymmetrical glycinato arrangement with in-plane and axial glycinato as well as in-plane and axial η 4-1,3-butadiene coordination. [Ru II(hedta)(H 2O)] − (2), hedta 3− = N-hydrpxyethylenediaminetriacetate, is less discriminating for olefin structures, forming η 2 complexes with all eleven olefins and dienes mentioned for studies with 1. However, 2 does not undergo displacement of a carboxylate donor by the second olefin unit of a diene [Ru II(hedta)(diene)] − complexes possess a pendant non-coordinated olefin and on η 2-bound olefin in the complex, indicated by a normal Ru II(pac)(olefin)Ru II/III wave near 0.55 V. 相似文献
16.
The synthesis of the 3-heptyl, and the eleven isomeric 3-methylheptyl-Δ 8-tetrahydrocannabinols (3–7, R and S methyl epimers, and 8) has been carried out. The synthetic approach entailed the synthesis of substituted resorcinols, which were subjected to acid catalyzed condensation with trans- para-menthadienol to provide the Δ 8-THC analogue. The 1′-, 2′- and 3′-methylheptyl analogues (3–5) are considerably more potent than Δ 8-THC. The 4′-, 5′- and 6′-methylheptyl isomers (6–8) are approximately equal in potency to Δ 8-THC. 相似文献
17.
Accurate and precise determination of phospholipid composition by 31P NMR spectroscopy requires correct assignments and adequate spectral resolution. Because temperature and pH may affect chemical shifts ( δ), our first aim was to establish the temperature coefficient (Δ δ/Δ T) of common phospholipid classes when using sodium cholate as detergent. This parameter can then be used to aid in resonance assignments. The second goal was to investigate the pH dependence of δ so that, in addition to temperature, pH control can be used to minimize spectral overlap. For phosphatidylcholine, sphingomyelin, dihydrosphingomyelin and phosphatidylglycerol, δ values were invariant with pH and temperature. Whereas the Δ δ/Δ T for phosphatidylinositol was 4 × 10 −3 ppm/°C, regardless of pH, these coefficients were highly pH-dependent for phosphatidic acid, phosphatidylethanolamine and phosphatidylserine, exhibiting maximal variations with the deprotonation of the headgroup, particularly for phosphatidic acid. These trends indicate the importance of H-bonding on δ and Δ δ/Δ T for phospholipid resonances. 相似文献
18.
Magnetic field-dependent recombination measurements together with magnetic field-dependent triplet lifetimes (Chidsey, E.D., Takiff, L., Goldstein, R.A. and Boxer, S.G. (1985) Proc. Natl. Acad. Sci USA 82, 6850–6854) yield a free energy change Δ G(P +H − − 3P*) = 0.165 eV ±0.008 at 290 K. This does not depend on whether nuclear spin relaxation in the state 3P* is assumed to be fast or slow compared to the lifetime of this state. This value, being (almost) temperature independent, indicates Δ G(P +H − − 3P*) Δ H(P +H − − 3P*) and is consistent with Δ G( 1P* − P +H −) and Δ H( 1P* − 3P*) from previous delayed fluorescence and phosphorescence data, implying Δ G Δ H for all combinations of these states. 相似文献
19.
The reversible equilibrium conversion under H 2 of [RuCl(dppb) (μ-Cl)] 2 (1) to generate (η 2-H 2) (dppb) (μ-Cl) 3RuCl(dppb) in CH 2Cl 2 (dppb = Ph2P( CH2) 4PPh2) has been studied at 0–25 °C by UV-Vis and 31P{ 1H} NMR spectroscopy, and by stoppe kinetics; the equilibrium constant and corresponding thermodynamic parameters, and the forward and reverse rate constants at 25 °C have been determined. A measured Δ H° value of 0 kJ mol −1 allows for an estimation of an exothermicity of 60 kJ mol −1 for binding an η 2-H 2 at an Ru(II) centre; a Δ S° value of 60 J mol −1 K −1 indicates that in solution 1 contain s coordinated CH 2Cl 2. The kinetic and thermodynamic data are compared to those obtained from a previously studied hydrogenation of styrene catalyzed by 1. Preliminary findings on related systems containing Ph 2P(CH 2) 3PPh 2 and (C 6H 11) 2P(C 6H 11) 2 are also noted. 相似文献
20.
An improved synthetic procedure for pentabenzylcyclopentadiene Bz 5C 5H was developed. Six new organomolybdenum and organotungsten halides η 5-Bz 5C 5M(CO) 3X(M = Mo, W; X = Cl, Br, I) were syntesized through the reaction of η 5-Bz 5C 5M(CO) 3Li (derived from Bz 5C 5H, n-BuLi and M(CO) 6) with PCl 3, PBr 3 or I 2 and characterized by elemental analysis, IR and 1H NMR spectroscopy. The structure of η 5-Bz 5C 5Mo(CO) 3I was determined by single-crystal X-ray diffraction techniques. It crystallized in the monoclinic space groupp P2/ c with cell parameters a = 13.294(4), B = 15.147(4), C = 19.027(3) Å, β = 108.32(2)°, V = 3637(2) Å 3, Z = 4 and Dx = 1.50 g cm −3. The final R value was 0.035 for 4564 observed reflections. 相似文献
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