Cis-stilbene Research Articles

Estrogenic activity of multicyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) in vitro assays

A representative group of multicyclic aromatic hydrocarbons (MAHC) which can be further classified as bridged-ring (bridged-MAHC) or fused-ring (fused-MAHC) were examined for their ability to interact with the estrogen receptor of rainbow trout (rtER) in a hepatic cytosolic estrogen receptor competitive binding assay (cyto rtERαβ) and the vitellogenin (Vtg) mRNA gene activation liver slice assay. All five fused-MAHCs; naphthalene (NAFT), fluorene (FE), Fluoranthene (FAT), pyrene (PY), and 9,10-dihydroanthracene (DAC) had no estrogenic activity in the in vitro assays used. Five of the eight bridged-MAHCs; triphenylethylene (3PE), o-terphenyl (OTP), triphenylmethane (TPM), 1,1-diphenylethylene (DPE), and cis-stilbene (CSB) were positive in the rtER-binding assay. The additional three bridged-MAHC’s; trans-stilbene (TSB), tetraphenylethylene (4PE), and 4,4-di-tertbutylphenyl (DtBB) were determined to be non-binders due to isomeric configuration, solubility limitation, and possible steric hinderance. It is possible that the bridged-MAHCs bind to the rtER through a proposed aromatic-aromatic stacking (π-π interaction) facilitated by perpendicular ring orientation achieved through free rotation of the bridged rings. The fused-ring structures are locked in a planar configuration which doesn’t allow for rotation of rings perpendicular to one another. This first report of the rtER-binding of bridged-MAHCs in fish demonstrates binding for a class of chemicals normally not thought of as having an affinity for the estrogen receptor and further supports the versatility or promiscuity of ER ligand selectivity.

Trans- and cis-stilbene isolated in cryogenic argon and xenon matrices

Monomers of trans- (TS) and cis-stilbene (CS) were isolated in cryogenic argon and xenon matrices, and their infrared (IR) spectra were fully assigned and interpreted. The interpretation of the vibrational spectra received support from theoretical calculations undertaken at the DFT(B3LYP)/6-311++G(d,p) level of theory. In situ broadband UV irradiation of the matrix-isolated CS led to its isomerization to TS, which appeared in the photolysed matrices in both non-planar and planar configurations. The non-planar species was found to convert into the more stable planar form upon subsequent annealing of the matrices at higher temperature. TS was found to be photostable under the used experimental conditions. The structure of the non-planar TS form was assigned based on the comparison of its observed IR spectrum with those theoretically predicted for different conformations of TS. Chemometrics was used to make this assignment. Additional reasoning on the structure of the studied stilbenes is presented taking as basis results of the Natural Bond Orbital analysis.

Ring-Closing and Dehydrogenation Reactions of Highly Excited cis-Stilbene: Ultrafast Spectroscopy and Structural Dynamics

The ultrafast dynamics of highly excited cis-stilbene (CS) in a molecular beam is explored using femtosecond time-resolved mass spectrometry and structure-sensitive photoelectron spectroscopy. cis-Stilbene is initially pumped by a 6 eV photon to the 7(1)B state and the reaction is followed by ionization with a time-delayed 3 eV probe pulse. Upon excitation, cis-stilbene rapidly decays to the 3(1)B state, where it undergoes a ring-closing reaction to form 4a,4b-dihydrophenanthrene (DHP). Whereas 14% of the ionized CS molecules dissociate one hydrogen atom to form hydrophenanthrene, the ionized DHP molecules completely dehydrogenate in the ion state to produce hydrophenanthrene and phenanthrene with a 1:1 ratio. We determined the lifetimes of the 7(1)B state and the 3(1)B state of CS to be 167 and 395 fs, respectively.

Synthesis and biological evaluation of some stilbene derivatives

Several trans and cis stilbenes with substitution on the olefinic bridge were synthesized and characterized by IR, NMR and mass spectroscopy in an effort to obtain substances that could be more readily formulated. All the synthesized compounds were screened against Molt4/C8, CEM and L1210 cell lines. None of these compounds were endowed with pronounced cytostatic activity. However, Schiff derivatives emerged as cytostatic agents (IC50: 0.77–10 μg/ml) that deserve further investigation.

Surface-Isomerization Dynamics of trans-Stilbene Molecules Adsorbed on Si(100)-2×1

Photoinduced trans-cis isomerization studies of stilbene molecules in the gas phase have led to a precise understanding of the corresponding molecular dynamics. Yet, when such molecules are adsorbed on surfaces, these reactions are expected to be strongly modified as compared to what is know in the gas phase. In this work, a low temperature (5 K) scanning tunneling microscope (STM) is used to image the trans-stilbene molecules deposited on a Si(100)-2 x 1 surface at 12 K. trans-Stilbene undergoes conformational changes during the adsorption process such that four different stilbene conformers are observed: trans-stilbene (TS), cis-stilbene (CS), and two new conformers I(1) and I(2). Furthermore, electronic excitation of individual stilbene molecules, by means of tunnel electrons, is shown to activate specific reversible molecular surface isomerization (TS <--> I(1) and CS <--> I(2)) combined with diffusion across the surface. Calculated STM topographies, using the tight binding method, indicate that the CS and TS molecules are physisorbed. The molecular conformations of the surface isomers I(1) and I(2) are suggested to be analogous to transient states conformations of the stilbene molecule when stabilized by the silicon surface. The measurements of the molecular surface isomerization and diffusion reaction yields are used to build a qualitative potential energy surface of the various stilbene reactions. The molecular surface-isomerization dynamics is shown to be influenced by the type of dopant (n or p). This is related to surface charging, which reveals modifications in the stilbene ionization potential.

Synthesis of Binary Ti-Si Mixed Oxides Nanoparticles with Rutile Structure as Selective Catalyst for Epoxidation of Alkenes

The nanoparticles of Ti-Si mixed oxides (NTSO) with Rutile structure were prepared by sol-gel method in a mixture of alcohol and water as solvent. The solid product was characterized by XRD, FTIR, SEM, TEM, UV, TGA and laser Raman spectroscopy. The catalytic activity of NTSO (5-10 nm) was investigated in the epoxidation of cis stilbene, trans stilbene, and norbornene by using oxidants such as tert-butylhydroperoxide (TBHP), molecular oxygen (O2)/isobutyraldehyde (IBA) and hydrogen peroxide (H2O2). It was found that epoxides of trans-stilbene and norbornene were formed quantitatively with the green H2O2 oxidant during 12 h.

C1score-level photoemission spectra of stilbene onSi(100)2×1surface from first-principles calculations

Adsorption of the cis and trans stilbene on the $\mathrm{Si}(100)2\ifmmode\times\else\texttimes\fi{}1$ surface was studied using plane waves density functional theory (DFT). Configurations across a silicon dimer, along the dimers and along the channels between dimers were probed for the two isomers. Trans and cis stilbene both bind preferentially across the dimers. In the former case only the ethylenic carbon atoms are involved and the aromatic character is preserved. In the latter case the adsorption interaction involves also the two phenyl rings with the conversion to two 1,3-cyclohexadiene, yielding a more stable local minimum. The corresponding calculated C $1s$ core level shifts are distributed in an energy range of about $2.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The overall shape of the spectra of the two adsorbed isomers shows differences consistent with chemical changes observed upon adsorption. There is a good agreement between the simulated and the experimentally observed spectrum of trans stilbene on the Si surface.

Belt‐Shaped Unsaturated Cyclophanes: Synthesis and Properties of Benzannulenes Composed of cis‐Stilbene Units

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Experimental evidence for multiple oxidation pathways in the (salen) Mn-catalyzed epoxidation of alkenes.

The substrate electronic effects on the selectivity in the catalytic epoxidation of para-substituted cis stilbenes 2a-i were investigated by using (R,R)-[N,N'-bis(3,5-di-tBu-salicylidene)-1,2-cyclohexanediamine]manganese(III) chloride 1 in benzene as the catalyst with iodosobenzene as the terminal oxidant. A Hammett study of the selectivity results reveals a stronger electrophilic character than previously assumed in the (salen)Mn-catalyzed reaction. In general, the best correlations with the experimental values were obtained by using the Hammett sigma + values, which gave rho = -1.37 for the rate of cis-epoxide formation and rho = -0.43 for the rate of the stepwise process leading to the corresponding trans product. The reaction involves two separate pathways as indicated also by the competitive breakdown of the intermediate on the path to trans epoxide for methoxy-substituted substrates. The asynchronicity in the concerted pathway leading to cis epoxide is apparent for 4-methoxy-4'-nitrostilbene, which yields cis epoxide with 75% ee entirely as a result of electronic effects.

Kinetic parameters of lymphocyte microsomal epoxide hydrolase in carbamazepine hypersensitive patients: Assessment by radiometric HPLC

Idiosyncratic hypersensitivity reactions with carbamazepine have been postulated to be due to a deficiency of microsomal epoxide hydrolase (HYL1), although this is based on indirect evidence. Using 3H- cis stilbene oxide: (0.5 Ci/mmol) as a substrate, we have developed a radiometric HPLC assay sensitive enough to measure the kinetic parameters of HYL1 in lymphocytes. The intra-assay coefficient of variation was 8%. Enzyme activity has been measured in lymphocytes from six carbamazepine hypersensitive patients, six patients on carbamazepine without any adverse effects, and twelve drug-naive healthy volunteers. No significant difference was observed in three kinetic parameters of the enzyme among these three groups. The values for K m , V max, and intrinsic clearance ranged from 6.1–89.9 μM, 3.0–23.2 pmoles diol formed/min/mg protein, and 0.147–0.493 μl/min/mg protein. There was no difference in enzyme activity between patients currently on carbamazepine and healthy volunteers, indicating a lack of induction of lymphocyte HYL1 by carbamazepine. Co-incubation of lymphocytes with 1,1,1-trichloropropene oxide, an inhibitor of hepatic HYL1, resulted in an 82% inhibition of activity, similar to that observed with the hepatic enzyme. The healthy volunteers were genotyped as being either GSTM1 positive ( n = 6) or GSTM1 negative ( n = 6). This did not affect the kinetic parameters of lymphocyte microsomal epoxide hydrolase. Our results suggest that there is normal HYL1 activity in lymphocytes of hypersensitive patients using cis-stilbene oxide as a substrate.

Photosensitizers covalently anchored to the silica surface: Modulation of the excited state efficiency through electron transfer from the linking arm or from the surface

Benzophenone derivatives have been anchored on silica in different ways. The so obtained heterogeneous as well as the corresponding homogeneous triplet photosensitizers have been tested in the triplet state isomerization of trans to cis stilbene. A photoinduced electron transfer originating from the amino groups on the linking arm or on the silica surface is found to modulate the sensitizer efficiency.

PHOSPHORUS PENTACHLORIDE REACTIONS WITH CONJUGATED CARBONYL COMPOUNDS AND CONJUGATED OLEFINS

Abstract Phosphorus pentachloride was reacted with conjugated aromatic and carbonyl compounds. The conjugated aromatic compounds were cis and trans stilbene, and the carbonyl compounds were diphenylketene and 2,3,4,5,-tetraphenylcyclopentadiene. Two solvents used for these reactions were 1,1,2,2-tetrachlorethane and methylene chloride. Phosphorus pentachloride can dissociate into phosphorus trichloride and chlorine and our results indicated this was the reaction mechanism for phosphorus pentachloride reacting with 1,1,2,2-tetraphenylcyclopentadiene. With stilbene, cis and trans, the mechanism with phosphorus pentachloride was the sp3d2 octahedral complex mechanism. With diphenylketene the mechanism was the dissociation of phosphorus pentachloride into the phosphorus tetrachloro cation and the phosphorus hexachloro anion.

Epoxide hydrolase in the bulb mite Rhizoglyphus robini: properties and induction

Using styrene oxide as substrate, most of the epoxide hydrolase (EH) activity monitored in the bulb mite Rhizoglyphus robini was associated with the microsomal compartment. The microsomal and cytosolic EHs did not display any significant preference in hydrating trans stilbene oxide (TSO) and cis stilbene oxide (CSO). The microsomal EH, which has a Km value of 5×10-5M and pH optimum of 7.8, was sensitive to ethanol and its activity was inhibited to a moderate extent by 4-fluorochalcone oxide, TSO, CSO and trans-chalcone oxide at a level of 10-4M. Microsomal EH was considerably induced (4–5-fold) in mites feeding garlic and onion, or ingesting TSO-impregnated filter papers. Other epoxides like CSO, 2,4-dichlorostilbene oxide, methyl chalcone oxide and heptachlor epoxide displayed moderate induction levels (1.4–2.6-fold). Of the toxicants assayed only sodium phenobarbital was a potent inducer. Lindane, malathion and DDT did not stimulate EH activity and 3-methyl-cholanthrene was even inhibitory. A decrease in EH activity was observed with a number of phytochemicals tested such as sinigrin, flavone, menthol, trans-β-carotene, chalcone, allyl sulphide and trans-cinnamic acid.

ChemInform Abstract: Synthesis and Evaluation of Analogues of Z-1-(4-Methoxyphenyl)-2-(3,4, 5-trimethoxyphenyl)ethene as Potential Cytotoxic and Antimitotic Agents.

A series of stilbenes has been prepared and tested for cytotoxicity in the five human cancer cell lines A-549 non-small cell lung, MCF-7 breast, HT-29 colon, SKMEL-5 melanoma, and MLM melanoma. The cis stilbenes 6a-f proved to be cytotoxic in all five cell lines, with potencies comparable to that of combretastatin A-4. These cytotoxic compounds were all potent inhibitors of tubulin polymerization. The corresponding trans stilbenes 7b-f were inactive as tubulin polymerization inhibitors and were significantly less cytotoxic in the five cancer cell lines. In the dihydro series, 8b, 8c, and 8f were inactive as tubulin polymerization inhibitors, while 8a, 8d, and 8e were less active than the corresponding cis compounds 6a, 6d, and 6e. The lack of tubulin polymerization inhibitory activity and cytotoxicity displayed by the phenanthrene 23b, which was synthesized as a conformationally rigid analogue of the lead compound 1, indicates that the activity of the stilbenes is not due to a totally planar conformation. Similarly, inactivity of the conformationally restricted analogue 26 suggests that the biologically active conformation of 1a resembles that of the cis alkene 1. Additional inactive compounds prepared include the benzylisoquinoline series 28-32 as well as the protoberberines 38 and 39. Shortening the two-carbon bridge of 1a to a one-carbon bridge in the diphenylmethane 20 resulted in a decrease in cytotoxicity and tubulin polymerization inhibitory activity. Although the corresponding benzophenone 18 was as active as 1a as a tubulin polymerization inhibitor, it was less cytotoxic than 1a, and the benzhydrol 19 was essentially inactive. With the exception of the amide 15c, which displayed low antitubulin activity, all of the phenylcinnamic acid derivatives 14a-c and 15a-f were inactive in the tubulin polymerization inhibition assay. The acid 14b and the ester 15a were cytotoxic in several of the cancer cell cultures in spite of their inactivity as tubulin polymerization inhibitors.

Comparative studies of the effects of stilbene compounds on hepatic ornithine decarboxylase and S-adenosylmethionine decarboxylase induction in rats

trans-Stilbene oxide (TSO, 2 mmol/kg, ip.) induced ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) to 60-fold and 5-fold of the controls, respectively, in the liver of rats. Parallel to ODC induction, there was a marked increase in putrescine content to 50-fold of the control levels. cis-Stilbene oxide (CSO), a stereoisomer of TSO, also produced the induction of ODC and SAMDC and the increase in putrescine content. There was no difference in the ability to induce ODC and SAMDC between TSO and CSO with respect to the extents of induction and the time needed to reach maximal levels. trans-Stilbene (TS), a mother compound of TSO, did not show such an effect on ODC, while cis-stilbene (CS) induced both ODC and SAMDC. Treatment with glutathione inhibited TSO- and CSO-mediated induction of ODC and SAMDC. These findings add new information concerning the abilities of TSO, CSO and CS on hepatic polyamine metabolism.

Triplet energy transfer to cis and trans stilbene. A quantum mechanical approach

The T—T energy transfer from aromatic hydrocarbons to trans and cis stilbene has been treated by applying the Ulstrup and Jortner quantum mechanical description of electron transfer reactions. This approach, incorporating the relevant spectroscopic and theoretical information, accounts well for the experimental behavior of the energy transfer of trans and cis stilbene. The main features of the process appear to be determined by the (low frequency) twisting mode and by the (high frequency) stretching CC modes of donor and acceptor molecules.

Alkaloids of Tylophora II: Structural Studies

Structural studies on the six alkaloids isolated from Tylophora crebriflora (N. O. Asclepiadacease) are described here. Spectral data indicate that five of these alkaloids (A-E) possess the dibenzo[f, h]-pyrrolo[1,2b]isoquinoline skeleton known to be present in tylocrebrine. They differ in the number, nature, and distribution of the oxygen-bearing substiuents and in the presence or absence of a benzylic-type hydroxyl. An oxygen substitution pattern of 3, 4, 6, and 7 is suggested for Alkaloids A, B, and C and that of 2, 3, 4, 6, and 7 for Alkaloids D and E. Alkaloid F is shown to be a seco analog of tylocrebrine with a 1,2-diphenyl cis stilbene skeleton.

Studies of the elimination of 1,2-diaryl-4-dimethylaminobutan-2-ols—III

Abstract Configurations are assigned to isomeric 1,2-diaryl-4-dimethylamino-3-methylbut-1-enes on the basis of differences in the PMR characteristics of isomeric pairs. To aid the work, the influence of α-substituents upon vinylic chemical shifts in a series of cis and trans α-substituted stilbenes has been determined and interpreted in terms of probable conformations.

Zum Mechanismus der photochemischen Dehydrocyclisierung von Stilben

The photochemical dehydrocyclization of stilbene resulting in phenanthrene has been examined quantitatively. From measurements of rate and quantum yields, it follows that the reaction only starts from the cis form of the stilbene molecule. A new mechanism was suggested involving the short-lived first excited singlet state of cis stilbene.

The Oxidation of trans- and cis-Stilbene by tert-Butylhydroperoxide

The Oxidation of trans- and cis-Stilbene by tert-Butylhydroperoxide