Synthesis and calcium antagonist activity of 1,4-dihydropyridines containing phenylaminoimidazolyl substituents

Alkyl ester analogues of nifedipine, in which the ortho-nitrophenyl group at position 4 is replaced by 2-methylthio-1-phenylamino-5-imidazolyl substituent, were synthesized and evaluated as calcium-channel antagonists using the high K(+) contraction of guinea-pig ileal longitudinal smooth muscle. The results for the symmetrical esters showed that in the series of alkyl esters increasing the length of methylene chain in C-3 and C-5 ester substituents for more than two methylene units decreases activity. In the phenylalkyl ester series increasing the length of methylene chain also decreases activity. The results demonstrate that most of the compounds had similar activity to the reference drug nifedipine. In addition, two compounds, 5b and 5f were more active than the nifedipine.

Synthesis and Evaluation of Pharmacological Activities of 3, 5-Dialkyl 1, 4-Dihydro-2, 6-Dimethyl-4-Nitroimidazole-3, 5-Pyridine Dicarboxylates

New analogues of nifedipine, in which the 2-nitrophenyl group at position 4 is replaced by a 1-methyl-5-nitro-2-imidazolyl substituent, were synthesized. The symmetrical dialkyl 1, 4-dihydro-2, 6-dimethyl-4-(1-methyl-5-nitro-2-imidazolyl)-3, 5-pyridinedicarboxylates were prepared by a classical Hantzsch condensation. The asymmetrical analogues were synthesized using a procedure reported by Iwanami that involved the condensation of alkylacetoacetate with methyl-, ethyl- or isopropyl3-aminocrotonate and 1-methyl-5-nitroimidazole-2-carboxaldehyde. Calcium channel antagonist activities were determined in vitro using a guinea pig ileum longitudinal smooth muscle (GPILSM)assay. Many compounds exhibited superior, or equipotent, calcium antagonist activity (IC(50) = 10(-10) to 10(-13) M range) relative to the reference drug nifedipine (IC(50) = 1.09 +/- 0.12 x 10(-11) M). Antinociceptive effects of some compounds were evaluated by the mouse tail-flick assay in vivo. Results demonstrate that some of the compounds were active as an antinociceptive.

Synthesis and anti-inflammatory activity of new 1-methyl-4-(4-X-benzenesulfonyl)pyrrolo[2,3-d] imidazole-5-carboxylates

A series of 1-methyl-4-(4-X-arylsulfonyl)pyrrolo[2,3-d]imidazo-le-5-carboxylates were synthesized and tested as anti-inflammatory agents. Indomethacin was used as reference drug. Two of the synthesized compounds 7a and 7b had an effect equal to 0.1 of indomethacin. Our result showed that the electron-withdrawing substituents in the para position of the benzensulfonyl moiety increase activity.

Antifungal activity of the methanolic extract and alkaloids of Glaucium oxylobum

The methanolic extract and total alkaloids of the aerial parts of Glaucium oxylobum exhibited good activity against Microsporum gypseum, Microsporum canis, Trichophyton mentagrophytes and Epidermophyton floccosum. Four alkaloids, dicentrine, glaucine, protopine, and alpha-allocryptopine, were identified as the compounds responsible for the antifungal activity of this plant.

Direct labelling of octreotide with 99mTc: effect of different concentration of reducing agents and amount of sodium pertechnetate on radiolabelling efficiency

Octreotide, a synthetic analog of natural hormone somatostatin, was labelled with 99mTc. Labelling was accomplished by reduction of the cysteine bridge, which provided sulfhydryl groups for chelating with 99mTc. Sodium ascorbate and sodium dithionite in different concentrations were used as reducing agents. Different amounts of sodium pertechnetate were used for labelling of peptide. When the mass ratio of peptide and sodium ascorbate was 1:100 and the final concentration of dithionite in the labelling vial was 0.2-0.4 microg/microl with 0.18-1.48 GBq sodium pertechnetate more than 80% radiolabelling efficiency was confirmed by RP-HPLC, ITLC-SG and C18 Cartridge analysis. The stability of the 99mTc-peptide bond was evaluated by human serum challenge and that showed the stability was 90% after 4h.

Synthesis and calcium channel antagonist activities of 3-nitrooxyalkyl, 5-alkyl 1,4-dihydro-2,6-dimethyl-4-(1-methyl-5-nitro-2-imidazolyl)-3, 5-pyridinedicarboxylates

A group of racemic 3-[(2-nitrooxyethyl), (3-nitrooxypropyl), (4-nitrooxybutyl) or (1,3-dinitrooxy-2-propyl)], 5-methyl (ethyl or propyl) 1,4-dihydro-2,6-dimethyl-4-(1-methyl-5-nitro-2-imidazolyl)-3,5-pyridinedicarboxylates (18-29) were synthesized using modified Hantzsch reaction that involved the condensation of 2-nitrooxyethyl (8), 3-nitrooxypropyl (9), 4-nitrooxybutyl (10) or 1,3-dinitrooxy-2-propyl (13) acetoacetate with methyl (14), ethyl (15) or isopropyl (16) 3-aminocrotonate and 1-methyl-5-nitroimidazole-2-carboxaldehyde (17). In vitro calcium channel antagonist activities were determined using a guinea pig ileum longitudinal smooth muscle assay. Compounds 18-29 exhibited superior, or equipotent, calcium antagonist activity (IC50= 10(11) - 10(-13) M range) relative to the reference drug nifedipine (IC50 = 1.07 +/- 0.12 x 10(-11) M), which could serve as potential probes to investigate the in vivo release of nitric oxide which induces vascular muscle relaxation.

Synthesis and calcium antagonist activity of new 1,4-dihydropyridines containing nitrobenzylimidazolyl substituent in guinea-pig ileal smooth muscle

New alkyl ester analogues of nifedipine, in which the ortho-nitrophenyl group of position 4 is replaced by 1-(4-nitrobenzyl)-5-imidazolyl or 2-methylthio-1-(4-nitrobenzyl)-5-imidazolyl substituent, were synthesized and evaluated as calcium-channel antagonists using the electrically induced contraction of guinea-pig ileal longitudinal smooth muscle. Our results demonstrate that all compounds inhibited the contractile response of guinea-pig ileum to electrical stimulation and the IC50 value of the most potent compounds 6a and 6f were significantly lower than that of nifedipine. Therefore, they are more potent than nifedipine.

Radioprotective effects of 2-iminothiazolidine derivatives against lethal doses of gamma radiation in mice

Although thiol-containing compounds have long been known to possess radioprotective properties, their therapeutics utility is limited by their side effects at radioprotective doses. In this study, a series of 2-iminothiazolidine derivatives were prepared and their toxicity and radioprotective effects in NMRI mice were determined using the LD50/30 end point. The LD50 values, as determined by a Probit analysis, were between 11 and 14 mg/kg. For studying radioprotective effects, one-sixth of the toxic LD50 values were used, namely 2 and 2.2 mg/kg. To evaluate the radioprotective capabilities, mice were exposed to lethal doses of cobalt-60 gamma-radiation alone or in the presence of compounds. The percentage survival of mice at 30 days for these compounds compared to control mice were 10 to 30% when injected 15 and 30 minutes before gamma-irradiation. They were significant compared to the control group (P < 0.05). 2-Imino-3-(benzoylmethyl)thiazolidine derivatives showed different radioprotective effects when injected at different times before irradiation, but were not statistically significant from each other (P > 0.05).

Synthesis and calcium channel antagonist activity of nifedipine analogues containing 4(5)-chloro-2-methyl-5(4)-imidazolyl substituent

Dihydropyridine having substituted imidazole at 4-position in conjunction with various C3, C5 diesters have calcium channel antagonist activity. In this paper a group of dialkyl, dicycloalkyl and diaryl ester analogues of nifedipine, in which the ortho-nitro phenyl group at position 4 replaced by 2-methyl-4(5)-chloro-5(4)-imidazolyl substituent, were synthesized and evaluated as calcium channel antagonists using the high K+ contraction of guinea-pig ileal longitudinal smooth muscle (GPILSM). The results for the symmetrical ester series showed that increasing the length chain in C3 and C5 ester substituents increased activity. When increasing of the length or lipophilicity accompany with increasing the hindrance, the activity decreased. In asymmetrical diester series, the results showed when R1 is methyl or ethyl, increasing of the lipophilic property in R substituent increases the activity if this high lipophilicity don't accompany with steric hindrance. Our results demonstrate that in symmetrical and asymmetrical series aromatic compounds were more active than aliphatic compounds. In symmetrical diesters compounds, the most active compound was diphenylethyl ester derivative, that it was more active than the reference drug nifedipine. These structure activity data indicate that the 2-methyl-4(5)chloro-5(4)-imidazolyl moiety is bioisoester of 2-nitrophenyl and 2-chlorophenyl moieties.

Antituberculosis agents, I: Synthesis and antituberculosis activity of 2-aryl-1,3,4-thiadiazole derivatives

The design, synthesis and antituberculosis activity of a series of 2-aryl-5-methylthio-1,3,4-thiadiazoles (5a-b), ethyl alpha-(5-aryl)-1,3,4-thiadiazole-2-ylthio)acetates (8a-b) and related compounds are described. All of the compounds were tested against Mycobacterium tuberculosis strain H37Rv in comparison to rifampicin. Six compounds exhibited a very good activity (MIC < 6.25 micrograms/ml, % Inhibition = 100).

Antituberculosis agents II. Evaluation of in vitro antituberculosis activity and cytotoxicity of some 2-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole derivatives

Using the radiometric BACTEC 460-TB methodology, the minimum inhibitory concentration (MIC) of a series of 2-(1-methyl-5-nitro-2-imidazolyl-1,3,4-thiadiazole-5-alkylsulfides, alkylsulfoxides and alkylsulfones which had been reported previously as antifungal agents, were determined. Active compounds were also screened by serial dilution to assess toxicity to a VERO cell line. The results indicate that compounds bearing a primary alkylthio substitution displayed good antituberculosis activity (MIC = 3.13-6.25 microg/ml). Oxidation to sulfone abolished the antituberculosis activity in methyl and propyl derivatives while the ethylsulfonyl analogue was active (MIC = 1.56 microg/ml). The cytotoxic effects indicate that 2-(1-methyl-5-nitro-2-imidazolyl)-5-methylthio-1,3,4-thiadiazole was the least toxic compound (IC50 > 10 microg/ml). Generally, all compounds showed a low selectivity index.

The complestatins as HIV-1 integrase inhibitors. Efficient isolation, structure elucidation, and inhibitory activities of isocomplestatin, chloropeptin I, new complestatins, A and B, and acid-hydrolysis products of chloropeptin I

From the screening of a microbial extract library, isocomplestatin (1), a new axial-chiral isomer of complestatin (2) which is a known rigid bicyclic hexapeptide, was identified as a potent natural product inhibitor of HIV-1 integrase, a unique enzyme responsible for viral replication. Isocomplestatin showed inhibitory activities (IC(50)) in coupled 3'-end processing/strand transfer (200 nM), strand transfer (4 microM), and HIV-1 replication (200 nM) in virus-infected cells. Attempted large-scale isolation of 1 by the literature method, used for the isolation of complestatin, led to lower yield and limited availability. We have developed several new, two-step, high-yielding absorption/elution methods of isolation based on reverse-phase chromatography at pH 8 that are applicable to scales from one gram to potential industrial quantities. We have also discovered and determined the structure of two new congeners of 1, namely, complestatins A (4) and B (5), with almost equal HIV-1 integrase activity. They differ from 1 at C2' and C3' of the tryptophan moiety (residue F). Selective acid hydrolysis of chloropeptin I (3), itself a known acid-catalyzed rearranged isomer of 1 and 2 (8'- vs 7'-substitution in tryptophan residue F, respectively), an isomer of complestatin, and isocomplestatin resulted in a number of fragments (6-10) with retention of most of the HIV-1 integrase activity. The structure-activity relationship as revealed by these compounds could possibly lead to the design of better inhibitors or understanding of the HIV-1 integrase target.

Synthesis of a [18F]labeled chelidonine derivative as a possible antitumor agent

[(+/-)-[5bRS-(5b alpha, 6beta, 12b alpha)]-5b,6,7,12b,13,14-hexahydro-13-methyl[1,3]benzodioxolo[5,6-c]-1,3-dioxolo[4,5-1] phenanthridin-6-yl]-4-[18F]fluorobenzoate (6b) an aromatic ester of chelidonine was prepared as a possible PET radiotracer. Compound (6b) was prepared in no-carrier-added (n.c.a) form from the 4-N,N,N-trimethylanilinium triflate derivative (5) in one step. The best results were obtained using Kryptofix(2.2.2)/[18F] and DMSO as the solvent at 90 degrees C. Column chromatography afforded the desired compound in overall radiochemical yield of 65-70% (EOS) with a specific activity of about 3000 Ci/mmole and radiochemical purity greater than 95% in 15 min.

Synthesis and in vitro antifungal and cytotoxicity evaluation of thiazolo-4H-1,2,4-triazoles and 1,2,3-thiadiazolo-4H-1,2,4-triazoles

The increasing clinical importance of drug-resistant fungal pathogens has lent additional urgency to microbiological and antifungal research. Various thiazolo(or 1,2,3-thiadiazolo)thiosemicarbazides (2a-2e), 3-thiono-1,4-dihydrotriazolothiazoles-(or 1,2,3-thiadiazoles) (3a-3e), their related substituted thio-4H-1,2,4-triazoles (4a-4p) and sulfones (5a-5o) were synthesized. Most of the compounds tested for antifungal activity exhibited significant effects against Cryptococcus neoofrmans and Sacchromyces cerevisiae at MIC ranges of 0.53 to 12.5 micrograms/mL, whereas their activities were moderate against Candida albicans and weak against Aspergillus fumigatus. At 10 ppm concentration, all compounds showed low toxicity on brine shrimps (higher than 80% survival), except compounds 4c and 2c. At 100 ppm concentration most of the compounds showed toxicity except compounds 2b, 2e, 3c, 3d, 3e, and 4e. Compounds 4b, 4c, and 4h showed in vitro cytotoxicity against Kbalb cell lines and compounds 4c and 4g against 143B cell lines at 0.1 mM concentration.

Inhibition of retinal angiogenesis by peptides derived from thrombospondin-1

PURPOSE

Thrombospondin (TSP)1 is a tumor suppressor with activity that is associated with its ability to inhibit neovascularization. Previous studies have mapped this antiangiogenic activity to the type 1 repeats and the amino-terminal portion of the molecule within the procollagen-like domain. The present study was performed to investigate the ability of TSP-1 and peptides derived from the type 1 repeats to inhibit retinal angiogenesis.

METHODS

TSP-1 and peptides with tryptophan-rich, heparin-binding sequences and transforming growth factor (TGF)-beta1 activation sequences were evaluated in two models of retinal angiogenesis: a retinal explant assay and a rat model of retinopathy of prematurity (ROP).

RESULTS

Platelet-derived TSP-1 inhibited angiogenesis in both experimental models. Peptides from the native TSP-1 sequence, which contained both the tryptophan-rich repeat and the TGF-beta1 activation sequence, were the most potent inhibitors of endothelial cell outgrowth in the retinal explant assay. In contrast, a peptide containing only the tryptophan-rich, heparin-binding sequence was most active in inhibiting neovascular disease in the rat ROP model.

CONCLUSIONS

These results indicate that the type 1 repeats of TSP-1 contain two subdomains that may independently influence the process of neovascularization, and that peptides derived from these type 1 repeats may be promising pharmacologic agents for treatment of retinal angiogenesis.

New pyrrolizidine alkaloids from Heliotropium crassifolium

Heliotropium crassifolium Boiss, (Boraginaceae) from a population of Ilam, western region of Iran was studied for pyrrolizidine alklaoids (PAs). Four alkaloids have been identified: europine 1, europine N-oxide 2 and a new pyrrolizidine alkaloids ilamine 3 and its N-oxide 4, respectively. Their structures were elucidated by IR, 1H-NMR and EIMS data.