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PubMed2001

Specific structural determinants are responsible for the antioxidant activity and the cell cycle effects of resveratrol.

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a natural phytoalexin found in grapes and wine, which shows antioxidant and antiproliferative activities. In this study we have investigated whether these properties are dependent on similar or different structural determinants of the molecule. To this purpose, resveratrol derivatives, in which all or each single hydroxylic function were selectively substituted with methyl groups, were synthesized. Analogues with the stilbenic double bond reduced or with the stereoisometry modified were also investigated. The antioxidant activity of these compounds was evaluated by measuring the inhibition of citronellal thermo-oxidation, or the reduction of 2,2-diphenyl-1-picrylhydrazyl radical. In addition, the protection against lipid peroxidation was determined in rat liver microsomes, and in human primary cell cultures. The antiproliferative activity was evaluated by a clonogenic assay, and by analysis of cell cycle progression and DNA synthesis. The results showed that the hydroxyl group in 4' position is not the sole determinant for antioxidant activity. In contrast, the presence of 4'-OH together with stereoisometry in the trans-conformation (4'-hydroxystyryl moiety) was absolutely required for inhibition of cell proliferation. Enzymatic assays in vitro demonstrated that inhibition of DNA synthesis was induced by a direct interaction of resveratrol with DNA polymerases alpha and delta.

Animals↗
PubMed2001

Inhibitory analogs of ubiquinol act anti-cooperatively on the Yeast cytochrome bc1 complex. Evidence for an alternating, half-of-the-sites mechanism of ubiquinol oxidation.

The cytochrome bc(1) complex is a dimeric enzyme that links electron transfer from ubiquinol to cytochrome c by a protonmotive Q cycle mechanism in which ubiquinol is oxidized at one center in the enzyme, referred to as center P, and ubiquinone is re-reduced at a second center, referred to as center N. To understand better the mechanism of ubiquinol oxidation, we have examined the interaction of several inhibitory analogs of ubiquinol with the yeast cytochrome bc(1) complex. Stigmatellin and methoxyacrylate stilbene, two inhibitors that block ubiquinol oxidation at center P, inhibit the yeast enzyme with a stoichiometry of 0.5 per bc(1) complex, indicating that one molecule of inhibitor is sufficient to fully inhibit the dimeric enzyme. This stoichiometry was obtained when the inhibitors were titrated in cytochrome c reductase assays and in reactions of quinol with enzyme in which the inhibitors block pre-steady state reduction of cytochrome b. As an independent measure of inhibitor binding, we titrated the red shift in the optical spectrum of ferrocytochrome b with methoxyacrylate stilbene and thus confirmed the results of the inhibition of activity titrations. The titration curves also indicate that the binding is anti-cooperative, in that a second molecule of inhibitor binds with much lower affinity to a dimer in which an inhibitor molecule is already bound. Because these inhibitors bind to the ubiquinol oxidation site in the bc(1) complex, we propose that the yeast cytochrome bc(1) complex oxidizes ubiquinol by an alternating, half-of-the-sites mechanism.

Anti-Bacterial Agents↗
PubMedDate not supplied

Oestrogen radioreceptor assay for multi-residue screening of bovine urine for oestrogenic anabolic compounds.

An improved radioreceptor assay (RRA), based on the method originally described by Korenman (1968), was used for the screening of urine samples of cattle for the presence of exogenous oestrogenic anabolic compounds, i.e. stilbenes and zeranol. The method includes extraction of the hormones from urine samples with a simultaneous purification using reversed-phase C18 cartridges. HPLC is used to isolate the anabolics from the naturally occurring oestrogens. Fractions containing the stilbenes and zeranol are collected and subsequently quantified using the RRA with the oestrogen receptor, isolated from immature calf uteri, as binder and tritiated 17 beta-oestradiol as tracer. Urine samples from untreated calves and cows, as well as samples from calves treated with zeranol/trenbolon acetate, dienoestrol or hexoestrol or samples containing diethylstilboestrol, were analysed using this RRA method. Sensitivity, specificity and predictive values were calculated at different classification levels (0.4, 0.5, 0.6 and 1.0 ng 'apparent' oestradiol per ml urine). An optimum sensitivity (89%) with a maximum specificity (95%) was reached at a classification level of 0.6 ng/ml. At this level the detection limits in urine samples are 0.5 ng/ml for hexoestrol, 0.6 ng/ml for diethylstilboestrol, 0.9 ng/ml for dienoestrol and 5.0 ng/ml for zeranol.

Anabolic Agents↗
PubMed1982

Stoichiometry of a half-turnover of band 3, the chloride transport protein of human erythrocytes.

The kinetics of human red blood cell Cl transport have been studied under nonequilibrium conditions to determine whether or not an outward Cl gradient can recruit the transport protein from an inward-facing to an outward-facing configuration. Three kinds of evidence are consistent with this outward recruitment. First, the initial net Cl efflux into a Cl-free phosphate medium is independent of the intracellular Cl concentration in the range 20-170 mM. Second, an outward Cl gradient strongly enhances the inhibitory potency of DNDS (4,4'-dinitro-2,2'-stilbene disulfonate), which suggests that DNDS binds primarily to outward-facing states. Finally, we have estimated the number of Cl ions transported during the putative outward recruitment. Resealed red cell ghosts containing only 70 muM 36Cl were resuspended at 0 degrees C in a Cl-free, HCO3-free Na2SO4 medium. In the first 10 s, or approximately 10(6) Cl ions per ghost, followed by a much slower further loss of Cl. The rapid loss of 10(6) Cl ions per ghost, which is abolished by pretreatment with DIDS (4,4'-diisothiocyano-2,2'-stilbene disulfonate), appears to represent the Cl that is transported during the first half-turnover of the transport cycle. These data are strong evidence that the influx and efflux events in the catalytic cycle for anion transport do not take place simultaneously, and that the stoichiometry of the transport cycle is close to one pair of anions exchanged per band 3 monomer.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1986

Oxidative microsomal metabolism of 1-nitropyrene and DNA-binding of oxidized metabolites following nitroreduction.

1-Nitropyrene is an environmental mutagen and carcinogen which undergoes both oxidative and reductive metabolism. We have previously shown that nitroreduction to N-hydroxy-1-aminopyrene leads to the formation of arylamine--DNA adducts. In the present study, we have investigated the oxidative metabolism of 1-nitropyrene and the subsequent binding of ring-oxidized metabolites to DNA. In vitro incubations were conducted using hepatic microsomes from uninduced rats or from rats pretreated with phenobarbital, Aroclor 1254, 3-methylcholanthrene, or 3-methylcholanthrene and trans-stilbene oxide. H.p.l.c. analysis of the incubation mixtures indicated the presence of the previously reported metabolites, 1-aminopyrene, 3-, 6-, and 8-hydroxy-1-nitropyrene, and 1-nitropyrene trans-4,5-dihydrodiol. In addition, 1-nitropyrene 4,5-oxide, 1-nitropyrene 9,10-oxide, 1-nitropyrene trans-9,10-dihydrodiol and 1-pyrenol were identified. The formation of both K-region dihydrodiols could be increased by trans-stilbene oxide induction of microsomal epoxide hydrase. Formation of the K-region epoxides was greatest using phenobarbital- and Aroclor-induced microsomes and increased with increasing oxygen tension, while 1-pyrenol formation was highest in 3-methylcholanthrene-induced microsomal incubations and was not affected by the oxygen tension. When calf thymus DNA was added to the microsomal incubations, similar levels of DNA-binding occurred in incubations conducted under oxygen, air, argon or anaerobic conditions. H.p.l.c. analysis of the enzymatically hydrolyzed DNA indicated the presence of multiple DNA adducts with the major product coeluting with N-(deoxyguanosin-8-yl)-1-aminopyrene. The K-region oxides bound directly to DNA to give adducts similar to the minor products detected in the microsomal incubations. Incubation of the K-region oxides with the nitroreductase, xanthine oxidase, increased the DNA-binding and resulted in an additional adduct which coeluted with N-(deoxyguanosin-8-yl)-1-amino pyrene. 3-Hydroxy-1-nitropyrene bound extensively to DNA upon nitroreduction by rat liver cytosol or xanthine oxidase, while 6- and 8-hydroxy-1-nitropyrene bound only slightly. None of these oxidized metabolites was activated to DNA-binding species by cytosolic nitroreduction followed by AcCoA-dependent acetylation. The fact that oxidized metabolites of 1-nitropyrene are reduced to DNA-binding derivatives more easily than 1-nitropyrene itself may be important in vivo where 1-nitropyrene has been shown to be readily oxidized.

Acetylation↗
PubMed2005

Does resveratrol prevent free radical-induced acute pancreatitis?

OBJECTIVE: The purpose of this study was to examine protective and antioxidative effect of stilbene derivatives, resveratrol and diethylstilbestrol, in experimental acute pancreatitis (EAP). METHODS: EAP was induced in male Wistar rats by retrograde injection of tert-butyl hydroperoxide (ButOOH) solution, a well-known prooxidant agent, into the common bile pancreatic duct. After a 3-hour observation, the animals were killed. Blood samples were collected. Each pancreas was removed and weighed. Tissue samples were taken for microscopic studies. The carbonyl and sulfhydryl (SH) group levels were estimated in the homogenate. RESULTS: Examination using light microscopy revealed morphologic changes in pancreata removed from EAP rats, namely focal edema, acinar cell vacuolization, and focal necrosis of pancreatic acini. The electron microscopic analysis also showed changes in their subcellular structures: dilated cisternae of the rough endoplasmic reticulum, swollen mitochondria, and "debris" of mitochondrial cristae. These changes corresponded with higher activities of serum amylase and tissue carbonyl groups levels and decreased SH group level compared with controls. Changes in pancreata were much less pronounced in the rats that received resveratrol or diethylstilbestrol for 8 days prior to ButOOH injection. CONCLUSION: Stilbene derivatives prevent pancreatic cells from structural changes during ButOOH-induced acute pancreatitis.

Acute Disease↗
PubMed2006

Pathway engineering for healthy phytochemicals leading to the production of novel flavonoids in tomato fruit.

Flavonoids are a large family of plant polyphenolic secondary metabolites. Although they are widespread throughout the plant kingdom, some flavonoid classes are specific for only a few plant species. Due to their presumed health benefits there is growing interest in the development of food crops with tailor-made levels and composition of flavonoids, designed to exert an optimal biological effect. In order to explore the possibilities of flavonoid engineering in tomato fruits, we have targeted this pathway towards classes of potentially healthy flavonoids which are novel for tomato. Using structural flavonoid genes (encoding stilbene synthase, chalcone synthase, chalcone reductase, chalcone isomerase and flavone synthase) from different plant sources, we were able to produce transgenic tomatoes accumulating new phytochemicals. Biochemical analysis showed that the fruit peel contained high levels of stilbenes (resveratrol and piceid), deoxychalcones (butein and isoliquiritigenin), flavones (luteolin-7-glucoside and luteolin aglycon) and flavonols (quercetin glycosides and kaempferol glycosides). Using an online high-performance liquid chromatography (HPLC) antioxidant detection system, we demonstrated that, due to the presence of the novel flavonoids, the transgenic tomato fruits displayed altered antioxidant profiles. In addition, total antioxidant capacity of tomato fruit peel with high levels of flavones and flavonols increased more than threefold. These results on genetic engineering of flavonoids in tomato fruit demonstrate the possibilities to change the levels and composition of health-related polyphenols in a crop plant and provide more insight in the genetic and biochemical regulation of the flavonoid pathway within this worldwide important vegetable.

Antioxidants↗
PubMed1997

Distance-dependent electron transfer in DNA hairpins.

The distance dependence of photoinduced electron transfer in duplex DNA was determined for a family of synthetic DNA hairpins in which a stilbene dicarboxamide forms a bridge connecting two oligonucleotide arms. Investigation of the fluorescence and transient absorption spectra of these hairpins established that no photoinduced electron transfer occurs for a hairpin that has six deoxyadenosine-deoxythymidine base pairs. However, the introduction of a single deoxyguanosine-deoxycytidine base pair resulted in distance-dependent fluorescence quenching and the formation of the stilbene anion radical. Kinetic analysis suggests that duplex DNA is somewhat more effective than proteins as a medium for electron transfer but that it does not function as a molecular wire.

Base Composition↗
PubMed1989

Conductive pathways for HCO3- in basolateral membrane of salamander intestinal cells.

To understand the route of HCO3- exit across the basolateral membrane of Amphiuma small intestinal cells during active H+ secretion the influence of bath HCO3- on serosal membrane potential (Vs) was measured using conventional microelectrodes. The villus sheet preparation was used, which allowed direct access to the basal membrane for microelectrode impalement. When tissues were incubated in Cl(-)-free (SO2-4 based) medium, Vs averaged -85.8 mV. Elevation of serosal bath [HCO3-] at constant CO2 increased Vs; reduction of the [HCO3-] reduced Vs and increased the fractional resistance of the serosal membrane. When serosal bath HCO3- and CO2 were completely replaced, Vs was -44.8 mV. The serosal membrane was also depolarized on complete replacement of medium HCO3- and CO2 when bath pH was buffered with phosphate. 4,4'-Dinitro-2,2'-stilbene disulfonate (DNDS) and acetazolamide blocked the decline in Vs produced by lowering serosal medium [HCO3-]. Replacement of serosal Na+ reduced Vs 32.7 mV. DNDS blocked this response. It is concluded that a Na+-dependent, stilbene-sensitive HCO3- exit pathway resides in the basolateral membrane of the intestinal cells. Possibly there is also a parallel, conductive pathway for HCO3-.

Acetazolamide↗
PubMed1991

Colonic Cl channel blockade by three classes of compounds.

We compared the potency and inhibitory actions of three different classes of organic acids on a Cl channel derived from colonic enterocyte plasma membrane vesicles. Chloride channels were incorporated into planar lipid bilayer membranes to examine the effects of the anthranilic acids, diphenylamine 2-carboxylic acid (DPC) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), the indanyl alkanoic acids, 2-[(2-cyclopentyl-6,7-dichloro-2,3-dihydro-2-methyl-1-oxo-1H-inden -5-yl)oxy] acetic acid (IAA-94) and its stereoenantiomer IAA-95, and the disulfonic stilbene, 4,4'-dinitro-stilbene-2,2'-disulfonic acid (DNDS). Except for DNDS, each of the blockers was equipotent from both the outer membrane and the cytoplasmic side of the channel protein. The potency order from the outmembrane side was DNDS greater than IAA-94 = IAA-95 greater than NPPB much greater than DPC. In contrast, the potency order from the cytoplasmic side was IAA-94 = IAA-95 greater than NPPB greater than DNDS much greater than DPC. DPC and NPPB caused a concentration-dependent decrease in the single-channel conductance (fast block). DNDS, IAA-94, and IAA-95 caused a flickery-type block and a concentration-dependent decrease in open-channel probability. Kinetic analysis revealed that blockade could be explained by a linear closed-opened-blocked kinetic scheme. Similarities in the electrostatic potential maps of these open-channel blockers suggest they may bind to a single shared binding site within the channel protein.

Animals↗
PubMed1992

Chloride is required for fluid transport by the rabbit corneal endothelium.

The role of chloride in fluid transport of the rabbit corneal endothelium was examined by measuring changes in corneal thickness following ion substitutions or addition of ion transport inhibitors in media superfusing the isolated tissue. Normal fluid transport is indicated by maintenance of constant thickness in a fresh cornea or thinning (deturgescence) of a preswollen deepithelialized cornea to its initial thickness at approximately 40 microns/h. These patterns are seen when tissues are superfused with HCO(3-)-Ringer containing 114 mM Cl-. When Cl- was substituted with gluconate, glucuronate, or SO4(2-) fresh and preswollen corneas immediately thinned at greater than 150 microns/h to a value less than 300 microns and then began to swell at 30 microns/h to above their original thickness. Substitution of Cl- with NO3- or Br- had a negligible immediate thinning effect, but fresh corneas subsequently swelled and preswollen corneas failed to deturgesce fully. The rapid thinning (called a "downtransient") observed with gluconate, glucuronate, and SO4(2-) also occurred in these media when ion and fluid transport were completely inhibited with ouabain or stilbenes or by absence of HCO3-, indicating that the thinning results from osmotic gradients induced by ionic reflection coefficients different from that of Cl-. When the downstransient was avoided in deepithelialized corneas by preswelling with the same Cl(-)-free media on both sides of the cornea, corneas maintained a constant but swollen thickness in gluconate and in NO3- or Br- deturgesced slowly and incompletely; ouabain or stilbenes caused further swelling in all media. We conclude that absence of Cl- partially impairs fluid transport, most probably via its role in a Cl(-)-HCO3- exchanger which has been proposed in a recent model of endothelial fluid transport.

Animals↗
PubMed1996

Substrate and inhibitor specificities of the monocarboxylate transporters of single rat heart cells.

We have used the intracellular pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to characterize the substrate and inhibitor specificity of monocarboxylate transport into isolated rat heart cells. Further evidence was obtained for the presence of two lactate carriers present in heart cells (Wang et al., Biochem. J. 290: 249-258, 1993) both distinct from the recently cloned monocarboxylate transporter isoform 1 (MCT-1) found in many other cell types. Only one isoform was potently inhibited by alpha-cyano-4-hydroxycinnamate [CHC; inhibitor constant (Ki) 190 microM] and the stilbene disulfonates 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (Ki 79 microM) and 4,4'-dinitrostilbene-2,2'-disulfonate (Ki of cis- and trans-isomers 38 and 171 microM, respectively; neither isomer inhibits MCT-1). The second carrier had a Ki of approximately 3 mM for CHC and 0.5-2 mM for the stilbene disulfonates. Thus, unlike in many other tissues, in rat heart cells these inhibitors are not effective at blocking lactate transport totally unless used at very high concentrations. Both carriers were inhibited by 3-isobutyl-1-methylxanthine (Ki 340 microM) and neither by 5-nitro-2-(3-phenylpropylamino)benzoate (a potent inhibitor of MCT-1). The overall Michaelis constant (Km) and maximum reaction rate (Vmax) for transport of a variety of substituted monocarboxylates (C2-C5) were determined, although it was not possible to elucidate the kinetic parameters of the two isoforms. Of physiological interest, the ketone bodies D-beta-hydroxybutyrate and acetoacetate had K(m) values of 10 and 5.4 mM, respectively. Vmax values were similar to those of L-lactate and pyruvate and indicate that transport could limit rates of utilization of ketone bodies. No stereoselectivity for L-over D-isomers of 2-chloro or 2-hydroxy acids was observed.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Inorganic anion transport in kidney and intestinal brush border and basolateral membranes.

The efflux of inorganic anions from purified brush border and basolateral membrane vesicles from dog kidney cortex was measured under equilibrium exchange conditions. Marked differences in temperature sensitivity and effects of inhibitors were found between the Cl and SO4 transport pathways and between the two types of membranes. SO4 transport in both brush border and basolateral membranes was markedly reduced by cooling, but significant inhibition by 4,4'-diisothiocyano-2,2'-disulfonic stilbene (DIDS) was only observed in basolateral vesicles. In contrast, Cl efflux from both types of vesicles was neither substantially inhibited by DIDS nor by lowering the temperature to 0 degrees C. Phosphate efflux from basolateral membrane vesicles was found to be only partially sensitive to DIDS. Attempts to label the stilbene-sensitive SO4 pathway in basolateral vesicles using [3H2]DIDS as a marker were unsuccessful due to the nonspecific labeling of many membrane components. The asymmetry in inorganic anion transport behavior exhibited by brush border and basolateral membrane vesicles from dog renal proximal tubule was also observed in equivalent vesicles prepared from rat small intestine.

Alkaline Phosphatase↗
PubMed2007

Pterostilbene, an active constituent of blueberries, suppresses aberrant crypt foci formation in the azoxymethane-induced colon carcinogenesis model in rats.

PURPOSE: Epidemiologic studies have linked the consumption of fruits and vegetables to reduced risk of several types of cancer. Laboratory animal model studies have provided evidence that stilbenes, phenolic compounds present in grapes and blueberries, play a role in inhibiting the risk of certain cancers. Pterostilbene, a naturally occurring stilbene from blueberries, was tested for its preventive activity against colon carcinogenesis. EXPERIMENTAL DESIGN: Experiments were designed to study the inhibitory effect of pterostilbene against the formation of azoxymethane-induced colonic aberrant crypt foci (ACF) preneoplastic lesions in male F344 rats. Beginning at 7 weeks of age, rats were treated with azoxymethane (15 mg/kg body weight s.c., once weekly for 2 weeks). One day after the second azoxymethane treatment, rats were fed experimental diets containing 0 or 40 ppm of pterostilbene. At 8 weeks after the second azoxymethane treatment, all rats were sacrificed, and colons were evaluated for ACF formation and for inhibition of inducible nitric oxide synthase (iNOS) and proliferating cell nuclear antigen. Effects on mucin MUC2 were also determined. RESULTS: Administration of pterostilbene for 8 weeks significantly suppressed azoxymethane-induced formation of ACF (57% inhibition, P < 0.001) and multiple clusters of aberrant crypts (29% inhibition, P < 0.01). Importantly, dietary pterostilbene also suppressed azoxymethane-induced colonic cell proliferation and iNOS expression. Inhibition of iNOS expression by pterostilbene was confirmed in cultured human colon cancer cells. CONCLUSIONS: The results of the present study suggest that pterostilbene, a compound present in blueberries, is of great interest for the prevention of colon cancer.

Animals↗
PubMed1979

Effects of anion-transport inhibitors on NaCl reabsorption in the rat superficial proximal convoluted tubule.

The effects of anion-transport inhibitors on volume reabsorption, and total CO(2) concentrations were examined by in vivo microperfusion of superficial proximal convoluted tubules of rats. The luminal perfusion solution was a high-chloride, low-bicarbonate solution like that in the in vivo late proximal tubule. The anion-transport inhibitors were only added to the luminal perfusion solutions. In tubules perfused with the control high-chloride solution, the rate of volume reabsorption (J(v)) was 2.3+/-0.2 nl/mm.min (n = 18), and the collected total CO(2) concentration was 4.0+/-0.3 mM. Furosemide (3 mM) caused a marked reduction in volume reabsorption to 0.8+/-0.3 nl/mm.min (n = 20) and only a slight increase in the total CO(2) concentration of collected samples of perfusate (7.8+/-0.5 mM). 0.8 mM acetazolamide caused a more pronounced rise in the collected total CO(2) concentrations to 10.7+/-0.5 mM but only a slight fall in J(v) to 1.7+/-0.3 nl/mm.min (n = 19). Hence, we inferred that inhibition of carbonic anhydrase only partially accounted for the inhibition of J(v) by furosemide. 4-acetamido-4'-iso-thiocyanato-stilbene-2,2'-disulphonic acid (0.1 mM), a well-characterized inhibitor of erythrocyte anion exchange mechanisms, also reduced J(v) to 1.6+/-0.3 nl/mm.min (n = 15) without changing the total CO(2) concentrations of the collected perfusates (3.6+/-0.4 mM). The effect of 4-acetamido-4'-iso-thiocyanato-stilbene-2,2'-disulphonic acid on volume reabsorption could not be explained by carbonic anhydrase inhibition because there was no increase in the total CO(2) concentration of the collected fluids. Furosemide did not significantly inhibit the rate of tracer glucose efflux out of the tubules, which suggests that the effect of furosemide on volume reabsorption was not a result of some nonspecific depression of active sodium transport. These results are discussed with respect to the possible effects of anion-transport inhibitors on the paracellular shunt pathway, active sodium reabsorption, and neutral sodium chloride transport.

Absorption↗
PubMed1995

Evaluation of the generation of genotoxic and cytotoxic metabolites of benzo[a]pyrene, aflatoxin B1, naphthalene and tamoxifen using human liver microsomes and human lymphocytes.

1. The ability of model stable epoxides and metabolites generated by human liver microsomes from benzo[a]pyrene, aflatoxin B1, naphthalene and tamoxifen to produce cytotoxicity and genotoxicity in human peripheral lymphocytes has been investigated. 2. The stable epoxides 1,1,1 trichloropropene-2,3-oxide (100 microM) and trans stilbene oxide (100 microM) as well as metabolites generated from aflatoxin B1 (30 microM) and naphthalene (100 microM) by an extracellular metabolising system were toxic to isolated resting mononuclear leucocytes (MNLs), whereas glycidol (100 microM), benzo[a]pyrene (100 microM) and tamoxifen (50 microM) were not. 3. The stable epoxides 1,1,1 trichloropropene-2,3-oxide (100 microM) and trans stilbene oxide (100 microM) but not glycidol (100 microM) were toxic to dividing lymphocytes only after a 72-h exposure. Tamoxifen (30 microM), aflatoxin B1 (30 microM) and their metabolites were also toxic to dividing lymphocytes. Benzo[a]pyrene (100 microM) and naphthalene (100 microM) were not toxic either in the absence or presence of the extracellular metabolising system. 4. Benzo[a]pyrene (100 microM) and aflatoxin B1 (30 microM) were directly genotoxic to lymphocytes, this genotoxicity was significantly enhanced by the presence of the extracellular metabolising system. This indicates that both intracellular and extracellular bioactivation of these two compounds can produce genotoxicity. In contrast, naphthalene and tamoxifen were non-genotoxic.

1-Propanol↗
PubMed2006

Studies on nepalese crude drugs. XXVIII. Chemical constituents of Bhote Khair, the underground parts of Eskemukerjea megacarpum HARA.

From the underground parts of Eskemukerjea megacarpum HARA, two new stilbenes (14, 15) were isolated, together with a known coumarin, 5,7-dihydroxycoumarin (1), a tyramine derivative, trans-feruloyltyramine (2), two pyrogallol derivatives, gallic acid (3) and beta-glucogallin (4), four flavonoids, trifolin (5), hyperin (6), myricetin 3-O-beta-D-galactopyranoside (7), and myricitrin (8), five stilbenes, resveratorol (9), astringenin (10), piceid (11) astringin (12), and resveratorol 3-O-beta-D-(6-O-galloyl)glucopyranoside (13), a flavan-3-ol, (-)-epigallocatechin 3-O-gallate (16), two proanthocyanidins, catechin-(4alpha-->8)-epigallocatechin 3-O-gallate (17) and epicatechin 3-O-gallate-(4beta-->8)-epigallocatechin 3-O-gallate (18), and an anthocyanin, idaein (19). Compounds 14 and 15 were identified as (E)-3,5,3',4'-tetrahydroxystilbene 3-O-beta-D-(6-O-galloyl)glucopyranoside and (E)-3,5,4'-trihydroxystilbene 3-O-beta-D-(6-O-galloyl)glucopyranoside, respectively, based on spectral and chemical data.

Coumarins↗
PubMed2003

A common structure of substrate shared by lignostilbenedioxygenase isozymes from Sphingomonas paucimobilis TMY1009.

A common structure of substrates of lignostilbenedioxygenases was investigated using synthesized stilbenes. Cell-free extracts of Sphingomonas paucimobilis TMY1009 degraded only trans-4-hydroxystilbene and trans-4-hydroxy-3-methoxystilbene. Other stilbenes that had no 4-hydroxyl group and had a cis structure were not substrates for lignostilbenedioxygenases. These results indicate that a 4-hydroxyl group and trans-structure is necessary for the common structure for substrates of lignostilbenedioxygenases.

Cell Extracts↗