Synthesis,radiolabeling and preliminary biological evaluation of radiolabeled 5-methyl-6-nitroquipazine,a potential radioligand for the serotonin transporter

5-Methyl-6-nitroquipazine, a novel analogue of the potent and selective serotonin transporter inhibitor 6-nitroquipazine was synthesized and radiolabeled with tritium and the positron emitter carbon-11. [³H]5-methyl-6-nitroquipazine was found to have a K_d=51±7 pM. The high affinity and the facile labeling of [¹¹C]5-methyl-6-nitroquipazine makes it a promising radioligand for visualization of the serotonin transporter with positron emission tomography.     

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 4: 3-Alkyl-4-halo-6-nitroquipazines

On the basis of the structure-activity relationship (SAR) of 4-chloro-6-nitroquipazine (Ki = 0.03 nM) and 3-fluoropropyl-6-nitroquipazine (Ki = 0.32 nM), 3-alkyl-4-halo-6-nitroquipazines were synthesized and tested for their potential abilities in vitro to displace [3H]citalopram binding to the rat cortical membranes. Binding affinities of 3b and 4d were Ki = 2.70+/-0.32 and 2.23+/-0.46 nM, respectively. The syntheses of 3-alkyl-4-halo-6-nitroquipazine, their in vitro binding affinities, and the SAR of C3, C4 position in 6-nitroquipazine are described.     

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 2: 4-substituted 6-nitroquipazines

Eleven 4-substituted derivatives of 6-nitroquipazine were synthesized and evaluated for their abilities to displace [3H]citalopram binding to the rat cortical synaptic membranes. Among them, 4-chloro-6-nitroquipazine was shown to possess the highest binding affinity (K(i=)0.03 nM) which was approximately 6 times higher than that of 6-nitroquipazine (K(i)=0.17 nM) itself. In this paper, we describe the syntheses of 4-substituted 6-nitroquipazine derivatives, the results of corresponding biological evaluation and the SAR study.     

Decreased viscosity of rat-liver DNA treated by 3'-methyl-4-dimethylaminoazobenzene, detected with a new viscometric approach

DNA damage induced in vivo by 3'-methyl-4-dimethylaminoazobenzene (3'CH3DAB) was investigated with 2 differently sensitive techniques: the alkaline elution assay and the viscometric measurement of DNA damage. 3'CH3DAB appeared to be falsely negative with the alkaline elution assay, whereas with the viscometric approach, which is about 30-50 times more sensitive, it appeared positive, and the DNA damage was dose-dependent.     

Change in the mixed function oxidase system of liver microsomes in rats treated with 3'-methyl-4-dimethylaminoazobenzene.

The mixed function oxidase systems of plasma membranes, the Golgi apparatus, and smooth and rough endoplasmic reticula of the livers of rats fed on a standard diet containing 0.06% (w/w) 3'-methyl-4-dimethylaminoazobenzene were investigated. The components and activities of the mixed function oxidase systems of the smooth endoplasmic reticulum and Golgi apparatus were especially reduced by the carcinogen. The activities for hydroxylation of anilines and demethylation of p-nitroanisole and the contents of cytochromes P-450 and b5 of the submicrosomal fractions of the rats decreased considerably more than the activities of NADH- and NADPH-ferricyanide reductases. More than 90% of the ferri-cytochrome P-450 content of the 3'-methyl-4-dimethylaminoazobenzene induced microsomes at 20 K was in the low spin form.     

Synthesis and biological activity of fungal metabolite, 4-hydroxy-3-(3'-methyl-2'-butenyl)-benzoic acid

4-Hydroxy-3-(3'-methyl-2'-butenyl)-benzoic acid (HMBA) was previously isolated from Curvularia sp. KF119 as a cell-cycle inhibitor. However, the present study used a novel and practical synthetic method to prepare a large quantity of HMBA. The synthetic HMBA was found to inhibit the cell-cycle progression of HeLa cells with a comparable potency to the natural fungal metabolite. The inhibition of the cell-cycle progression by the synthetic HMBA involved both the activation of p21(WAFI) and the inhibition of cyclin Dl expression in the cells. Consequently, this new synthetic procedure provides an easy and convenient way to produce or manipulate the original fungal metabolite.     

Promoting effect of ovariectomy on hepatocellular tumorigenesis induced in mice by 3'-methyl-4-dimethylaminoazobenzene.

The treatment of female C57BL/6 x DS-F1 mice with 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) at 10, 12, 14, 16 and 18 days of age resulted in the development of hepatocellular adenomatous nodules after 10 months of age. Ovariectomy in these mice at 1 month of age hastened the development of adenomatous nodules, which then first appeared at 8 months of age. The incidence of adenomatous nodules in females ovariectomized at the age of 1 month was much higher than that in intact females of the same age. These results showed that the ovaries exerted a suppressive effect on the development of adenomatous nodules. To determine the time from which the ovaries exert this suppressive effect, females were ovariectomized at 4, 6, 8, and 10 months of age, and the incidences of adenomatous nodules were compared at 10 and 12 months of age. Delayed ovariectomy after 8 months of age did decrease the incidence of adenomatous nodules at 10 and 12 months of age, but ovariectomy after 4 and 6 months of age did not. When the incidence of adenomatous nodules in females ovariectomized at 10 months of age was examined over the subsequent 6 months, it became significantly higher after 14 months of age compared with that in intact females. The results show that the ovariectomy has the promoting effect on the development of adenomatous nodules in the liver induced by 3'-Me-DAB after 6 months of age.     

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 1

6-Nitroquipazine has been known as one of the most potent and selective inhibitors of serotonin transporter in vitro and in vivo. Nine derivatives of 6-nitroquipazine were synthesized and tested for their potential abilities to displace [3H]citalopram binding to the rat cortical membranes.     

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 5: 2'-Substituted 6-nitroquipazines

Five C2'-substituted 6-nitroquipazine (6-NQ) derivatives were prepared and evaluated in terms of their biological abilities (K(i)) to displace [(3)H]citalopram binding to serotonin transporter. The relationship between their structure and biological activities revealed that shorter alkyl groups tend to possess higher binding affinity. Both compounds 12a and 12c were found to have the equally highest binding affinity (K(i)=0.43+/-0.02 nM).     

Synthesis and monoamine transporter binding properties of 2beta-[3'-(substituted benzyl)isoxazol-5-yl]- and 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes

A series of 2beta-[3'-(substituted benzyl)isoxazol-5-yl]- and 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes were prepared and evaluated for affinities at dopamine, serotonin, and norepinephrine transporters using competitive radioligand binding assays. The 2beta-[3'-(substituted benzyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes (3a-h) showed high binding affinities for the dopamine transporter (DAT). The IC(50) values ranged from 5.9 to 22nM. On the other hand, the 2beta-[3'-methyl-4'-(substituted phenyl)isoxazol-5-yl]-3beta-(substituted phenyl)tropanes (4a-h), with IC(50) values ranging from 65 to 173nM, were approximately 3- to 25-fold less potent than the corresponding 2beta-[3'-(substituted benzyl)isoxazol]tropanes. All tested compounds were selective for the DAT relative to the norepinephrine transporter (NET) and serotonin transporter (5-HTT). 3Beta-(4-Methylphenyl)-2beta-[3'-(4-fluorobenzyl)isoxazol-5-yl]tropane (3b) with IC(50) of 5.9nM at the DAT and K(i)s of 454 and 113nM at the NET and 5-HTT, respectively, was the most potent and DAT-selective analog. Molecular modeling studies suggested that the rigid conformation of the isoxazole side chain in 4a-h might play an important role on their low DAT binding affinities.     

Synthesis of a fluorine-18-labelled derivative of 6-nitroquipazine,as a radioligand for the in vivo serotonin transporter imaging with PET

Considerable efforts have been engaged in the design, synthesis and pharmacological characterization of radioligands for imaging the serotonin transporter, based on its implication in several neuropsychiatric diseases, such as depression, anxiety and schizophrenia. In the 5-halo-6-nitroquipazine series, the fluoro derivative has been designed for positron emission tomography (PET). The corresponding 5-iodo-, 5-bromo- and 5-chloro N-Boc-protected quipazines as labelling precursors, as well as 5-fluoro-6-nitroquipazine as a reference compound have been synthesized. 5-[(18)F]Fluoro-6-nitroquipazine has been radiolabelled with fluorine-18 (positron-emitting isotope, 109.8 min half-life) by nucleophilic aromatic substitution from the corresponding N-Boc protected 5-bromo- and 5-chloro-precursors using K[(18)F]F-K(222) complex in DMSO by conventional heating (145 degrees C, 2 min) or microwave activation (50 W, 30-45 s), followed by removal of the protective group with TFA. Typically, 15-25 mCi (5.5-9.2 GBq) of 5-[(18)F]fluoro-6-nitroquipazine (1-2 Ci/micromol or 37-72 GBq/micromol) could be obtained in 70-80 min starting from a 550-650 mCi (20.3-24.0 GBq) aliquot of a cyclotron [(18)F]F(-) production batch (2.7-3.8% non decay-corrected yield based on the starting [(18)F]fluoride). Ex vivo studies (biodistribution in rat), as well as PET imaging (in monkey) demonstrated that 5-[(18)F]fluoro-6-nitroquipazine ([(18)F]-1d) readily crossed the blood brain barrier and accumulated in the regions rich in 5-HT transporter (frontal- and posterial cortex, striata). However, the low accumulation of the tracer in the thalamus (rat and monkey) as well as the comparable displacement of the tracer observed with both citalopram, a -HT re-uptake inhibitor and maprotiline, a norepinephrine re-uptake inhibitor (rat), indicate that 5-[(18)F]fluoro-6-nitroquipazine ([(18)F]-1d) does not have the suggested potential for PET imaging of the serotin transporter (SERT).     

3-Geranyl-4-hydroxy-5-(3'-methyl-2'-butenyl)benzoic acid as an anti-inflammatory compound from Myrsine seguinii.

Bioassay-guided isolation of anti-inflammatory compounds from the methanol extract of Myrsine seguinii yielded an anti-inflammatory compound (1). The structure of compound 1 was elucidated to be 3-geranyl-4-hydroxy-5-(3'-methyl-2'-butenyl)benzoic acid on the basis of its spectroscopic data. Compound 1 strongly suppressed 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation on mouse ears at a dose of 500 micrograms (inhibitory effect (IE): 65%). The acetate and the methyl ether of 1 showed moderate activity at a 500-microgram application, with IE 38% and 27%, respectively. However, the methyl ester and the dimethyl derivative of 1 did not show activity at the same dose. The related compounds of 1, o-, m- and p-hydroxybenzoic acids also did not exhibit notable activity. These results indicate that the carboxylic acid and lipophilic terpene moieties of 1 were significant structural features for anti-inflammatory activity.     

Bioactive constituents of Artemisia monosperma

During a study on the chemistry and biological activity of Kuwaiti plants, new metabolites including 4,6-dihydroxy-3-[3'-methyl-2'-butenyl]-5-[4'-hydroxy-3'-methyl-2'-butenyl]-cinnamic acid (1), the 3R,8R stereoisomer of the C17 polyacetylene dehydrofalcarindiol (2) and a C10 polyacetylene glucoside (3) were characterised by spectroscopic means. Additionally, the previously characterised natural products 1,3R,8R-trihydroxydec-9-en-4,6-yne (4), spathulenol (5) and eriodyctiol-7-methyl ether (6) were also isolated. Compounds 2, 3, and 4 were evaluated for their ability to inhibit the enzyme 12-lipoxygenase and 3 and 4 showed moderate activity at 30 microg/ml. Compound 2 was evaluated against a panel of colorectal and breast cancer cell lines and IC50 values ranged from 5.8 to 37.6 microg/ml. Against a panel of fast-growing mycobacteria and a standard ATCC strain of Staphylococcus aureus, compound 6 exhibited minimum inhibitory concentrations in the range of 64-128 microg/ml.     

Biosynthetic origins of the isoprene units of gaudichaudianic acid in Piper gaudichaudianum (Piperaceae)

The biosynthesis of (2S)-2-methyl-2-(4'-methyl-3'-pentenyl)-8-(3'-methyl-2-butenyl)-2H-1-benzopyran-6-carboxylic acid (gaudichaudianic acid), the major metabolite in leaves and roots of Piper gaudichaudianum Kunth (Piperaceae), has been investigated employing [1-(13)C]-D-glucose as precursor. The labelling pattern in the isolated gaudichaudianic acid was determined by quantitative (13)C NMR spectroscopy analysis and was consistent with involvement of both mevalonic acid and 2-C-methyl-D-erythritol-4-phosphate pathways in the formation of the dimethylallyl- and geranyl-derived moieties. The results confirmed that both plastidic and cytoplasmic pathways are able to provide isopentenyl diphosphate units for prenylation of p-hydroxybenzoic acid.     

Chemoenzymatic synthesis and antiviral evaluation of conformationally constrained and 3'-methyl-branched carbanucleosides using both enantiomers of the same building block

Starting from both enantiomers of a readily available building block, a straightforward enantioselective approach to constrained 3'-methyl-2',3'-alpha-oxirane-fused and 3'-methyl-3',4'-alpha-oxirane-fused carbanucleosides bearing different purine base analogues is described. The title compounds were evaluated as potential antiviral agents against important viruses. None of the new compounds had significant antiviral activity at a concentration of 100 microg/mL, which was the highest concentration tested.     

A chromene and prenylated benzoic acid from Piper aduncum.

In addition to nerolidol, 2',6'-dihydroxy-4'-methoxydihydrochalcone, methyl 2,2-dimethyl-8-(3'-methyl-2'-butenyl)-2H-1-chromene-6-carboxylate, methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate and methyl 8-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate, two new natural products were isolated from the leaves of Piper aduncum, 2,2-dimethyl-2H-1-chromene-6-carboxylic acid and 3-(3',7'-dimethyl-2',6'-octadienyl)-4-methoxybenzoic acid. The structures of the isolates were established based on analysis of spectroscopic data, including ES-MS. The DNA-damaging activity of the isolated compounds was also investigated against mutant strains of Saccharomyces cerevisiae.     

Protein composition of nuclear ribonucleoprotein particles isolated from liver of rats in the early stages of feeding of 3'-methyl-4-dimethylaminoazobenzene and from hepatoma induced by the same carcinogen.

The feeding of carcinogenic 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) in the early stages results in a change in the protein composition of the nuclear ribonucleoprotein particles of the rat liver. These particles are associated with newly synthesized RNA and it is assumed that they are involved in the processing and in the transport of this RNA. After 6 weeks of feeding of this azocarcinogen, the amount of one of the main polypeptides (apparent molecular weight 42 000) is decreased and after 10 weeks of feeding the particles are devoid of this polypeptide completely. Feeding of the non-carcinogenic p-aminoazobenzene (AB) is without any effect. The loss of this polypeptide is not characteristic for the malignant transformation. In the nuclear ribonucleoprotein particles isolated from hepatoma which has been induced by 3'-MeDAB this polypeptide is present in even higher proportion to other polypeptides than it is in particles isolated from liver cells of control animals. The 3'-MeDAB binds to the proteins of the liver nuclear ribonucleoprotein particles and interferes with the RNA processing. It is proposed that the changes in the composition of the protein moiety of the particles reflect changes in the population of liver cells leading finally to the selection of hepatoma cells which are resistant to the toxic effect of 3'-MeDAB on RNA processing.     

Xanthones from the bark of Garcinia merguensis

The bark of Garcinia merguensis yielded 10 xanthones, merguenone, 1,5-dihydroxy-6'-methyl-6'-(4-methyl-3-pentenyl)-pyrano(2',3':3,2)-xanthone, subelliptenone H, 8-deoxygartanin, rheediaxanthone A, morusignin G, 6-deoxyjacareubin, 1,3,5-trihydroxy-4,8-di(3-methylbut-2-enyl)-xanthone, rheediachromenoxanthone and 6-deoxyisojacareubin. The structure of merguenone was determined using spectroscopic techniques, mainly 1D and 2D NMR spectroscopy.     

A novel isoindoline,porritoxin sulfonic acid,from Alternaria porri and the structure-phytotoxicity correlation of its related compounds

Novel zinniol-related compound 3, named porritoxin sulfonic acid, with an isoindoline skeleton was isolated from the culture liquid of Alternaria porri. The structure was determined to be 2-(2"-sulfoethyl)-4-methoxy-5-methyl-6-(3'-methyl-2'-butenyloxy)-2,3-dihydro-1H-isoindol-1-one. The phytotoxic activities of three isoindolines (1-3) were evaluated in a seedling-growth assay against stone leek and lettuce.     

Synthesis of some newer derivatives of substituted quinazolinonyl-2-oxo/thiobarbituric acid as potent anticonvulsant agents

5-[1'-[3"-Aminoacetyl-2"-methyl-6",8"-dihalosubstitutedquinazolin-4"(3"H)-onyl]-thiosemicarbazido]-2-oxo/thiobarbituric acids 3a-3h and 5-[2'-amino-5'-[3"-aminomethylene-2"-methyl-6",8"-dihalosubstitutedquinazolin-4"(3"H)-onyl]-1',3',4'-thiadiazol-2'-yl]-2-oxo/thiobarbituric acid 5a-5h were prepared by incorporating 1-[3'-aminoacetyl-2'-methyl-6",8"-dihalosubstituted-quinazolin-4'(3'H)-onyl]-thiosemicarbazides 2a-2d and 2-amino-5-[3'-aminomethylene-2'-methyl-6',8'-dihalosubstituted-quinazolin-4'(3'H)-onyl]-1,3,4-thiadiazoles 4a-4 h respectively at 5(th) position of 2-oxo/thiobarbituric acids (via Mannich reaction). All the newly synthesized compounds were screened for their anti-convulsant activity in MES and PTZ models and were compared with standard drugs phenytoin sodium and sodium valproate. Interestingly, these compounds were found to be devoid of sedative and hypnotic activities when tested. Out of the compounds studied, the most active compound 5h, that is 5-[2'-amino-5'-[3"-aminomethylene-2"-methyl-6",8"-dibromoquinazolin-4"(3"H)-onyl]-1',3',4'-thiadiazol-2'-yl]-2-thiobarbituric acid showed activity (90%) more potent than the standard drug.