Medicinal Chemistry - Volume 3, Issue 3, 2007

Agaritine, or β-N-[γ-L(+)-glutamyl]-4-hydroxymethylphenylhydrazine, is a Chinese herbal medicine, known having the antiviral and anticancer function. However, so far no reports whatsoever have been made for its potential as an anti-HIV agent. It was observed by docking experiments for more than 9,000 compounds extracted from various Chinese medicines that the compound agaritine distinguished itself from all the others in binding to the HIV protease with the most favorable free energy. Based on this, a series of derivatives were generated by modifying agaritine. It has been observed thru an extensive docking study that some of agaritine derivatives had markedly stronger binding interaction with the HIV protease than agaritine, suggesting that these derivatives might be good candidates for developing drugs for AIDS therapy.

HIV-1 reverse transcriptase inhibitory activity of a series of substituted pyridinone derivatives (nonnucleoside) was subjected to classical QSAR study by using mixed approach (Hansch and Free-Wilson). The study was carried out with indicator parameter encoding different group contributions and some physico chemical parameters namely hydrophobic (π), electronic (σ), steric (MR) and STERIMOL values of aromatic substitutents. The best generated models were validated by leave-one- out technique (LOO-internal validation) and predicting the activity of the test (external validation). Further bootstrapping method was adopted to assess the robustness of the models. The analysis explores the substitutional requirements of the pyridinone moiety of the compounds for effective inhibition of HIV-1 RT enzyme.

Neoplastic cells exhibit defects in their ability to differentiate; therefore, differentiation therapy represents a viable option to control cancer growth and progression. Rhabdomyosarcomas (RMS), a malignant tumor of skeletal muscle, is the most common soft tissue sarcoma in children and is characterized by its poor response to cytotoxic treatment and significant morbidity. Since modulation of α-tubulin and human leukocyte antigen (HLA) class I expression has been detected during malignant transformation, we analyzed in this study the expression pattern of both kinds of proteins after the treatment with 5-FU derivatives in the human RMS RD cell line. Cytotoxic assays, scanning and transmission electron microscopy, flow cytometry and immunocytochemical analyses were used. The compounds analyzed belonged to the following three categories: (a) symmetrical bis(5-fluorouracil-1-yl) derivatives with a linker that connects the N1 atoms of both pyrimidine moieties by means of two amide bonds; and (b) an ester with the 5-FU base. The whole structure corresponds to the terminal fragment of the molecules included in (a) and (c) 5-fluorouracil acyclonucleoside-like structures. 1- {[3-(3-Chloro-2-hydroxypropoxy)-1-methoxy]propoxy]propyl}-5-fluorouracil (2), that belongs to the class (a) produced the highest increment of tubulin and its intense capillary distribution throughout the cytoplasm. On the other hand, N,Nbis[ 3-(5-fluorouracil-1-yl)-3-methoxypropanoyl]-α,α diamino-m-xylene (5) and 2 that are included in the class (c) caused the major percentage of marked cells by the HLA class I proteins. In short, our results showed that the 5-FU derivatives increase HLA class I expression and showed greater microtubule stability with an important network of tubulin beams related with the degree of differentiation of RD cells. These results could mean a more favorable prognosis of the patients affected with these tumors.

Substituted amidoalkyl derivatives of 2,3-diarylacrylophenones carrying the amide chain on the 3-aryl residue have been prepared by reacting corresponding phenolic 2,3-diarylacrylophenones with haloalkyl carboxylic acid esters, their hydrolysis and subsequent treatment with different alkyl amines. Compounds thus prepared were evaluated for their relative binding affinity (RBA) towards estrogen receptors (ER), estrogen agonistic and antagonistic activities. Out of eleven amide derivatives thus prepared, compounds 7, 13, 15-19, 23, 24 showed significant estrogen antagonistic activity. Interestingly the phenolic compound 7 and the acid ester 18 also exhibited estrogen inhibiting property. Majority of the dimethoxy derivatives (R = OCH3) showed significantly high estrogenic activity. In order to throw light on their SAR, In silico docking of the acrylophenone derivatives in the ligand binding site of the ERα and their comparison with pure steroidal estrogen antagonist ICI-164,384 and the non-steroidal antiestrogen raloxifene, was carried out. Crystal structure of compound 6 revealed relative trans-geometry of the 2(B) and 3(C) phenyl rings.

Backgrounds: The postmortem and magnetic resonance imaging studies for schizophrenic patients showed neuropathological abnormalities including neuron loss and volume reduction in ventral hippocampus (VH), some longitudinal studies suggest these changes may be a neurodegenerative process. Objectives: The present study examined the effects of adult bilateral VH lesions on a dopaminergic stimulant, methamphetamine (METH)-induced and an N-methyl-Daspartate (NMDA) receptor antagonist, dizocilpine (MK-801)-induced behavioral and neurochemical changes in rats, in order to evaluate a potential of adult VH lesion animals for a model of schizophrenia. Methods: To study the behavioral effects after bilateral VH lesions in adult rats, locomotor activity was measured individually by an infra-red sensor. Extracellular concentrations of dopamine in the nucleus accumbens (NAc) were measured using in vivo brain microdialysis. Results: The bilateral adult VH lesion rats showed a significant enhanced hyperlocomotion in response to METH but no changes to MK-801 and phencyclidine; while bilateral adult VH lesion enhanced METH-induced increasing dopamine levels in the NAc. Conclusions: The bilateral adult VH lesions enhanced locomotor activity, which related to increased dopamine releases in the NAc, induced by a dopaminergic stimulant; these findings may suggest a potential of adult VH lesion animal for a model reflecting dopamine D2 receptor antagonist-responsive pathophysiology of schizophrenia by way of neurodegenerative processes.

The implications of oxidative stress in the pathogenesis of many chronic human diseases has led to the widely accepted view that low molecular weight antioxidants could be beneficial and postpone or even prevent these diseases. Small molecules of either plant or synthetic origins, which contain Michael acceptor functionalities (olefins or acetylenes conjugated to electron-withdrawing groups) protect against the toxicity of oxidants and electrophiles indirectly, i.e., by inducing phase 2 cytoprotective enzymes. Some of these molecules, e.g., flavonoid and curcuminoid analogues that have phenolic hydroxyl groups in addition to Michael acceptor centers, are also potent direct antioxidants, and may therefore be appropriately designated: bifunctional antioxidants. By use of spectroscopic methods we identified phenolic chalcone and bis(benzylidene)acetone analogues containing one or two Michael acceptor groups, respectively, as very efficient scavengers of two different types of radicals: (a) the nitrogen-centered 2,2'-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS +) radical cation, and (b) the oxygen-centered galvinoxyl (phenoxyl) radical. The most potent scavengers are those also bearing hydroxyl substituents on the aromatic ring(s) at the ortho-position(s). The initial reaction velocities are very rapid and concentration-dependent. In the human keratinocyte cell line HaCaT, the same compounds coordinately increase the intracellular levels of glutathione, glutathione reductase, and thioredoxin reductase. Thus, such bifunctional antioxidants could exert synergistic protective effects against oxidants and electrophiles which represent the principal biological hazards by: (i) scavenging hazardous oxidants directly and immediately; and (ii) inducing the phase 2 response to prevent and resolve the consequences of hazardous processes that are already in progress, i.e., acting indirectly, but with much more diverse and long-lasting effects.

A new series of N-substituted 2-butyl-5-chloro-3H-imidazole-4-carbaldehyde derivatives were synthesized by using the different bioactive heteroaralkyl halides with 2-butyl-4-chloro-1H-imidazole-5-carbaldehyde in presence of powdered potassium carbonate in DMF medium. These compounds were screened for their antitumor activity. Our results show that treatment of imidazole derivatives inhibit proliferation EAT cells, decreases the ascites volume and increases the survivability of the animals in vivo. These compounds also inhibited the cellular proliferation of HUVEC cells in vitro by MTT assay. Further, these compounds could induce apoptosis, which is evident by the nuclear condensation of imidazole derivatives treated EAT cells in vivo by the cytological analysis. We have identified that pyrrolidine substituted imidazole derivative as potent anti-tumor compound. These inhibitors could represent as promising candidates for anticancer therapies, where the formation of peritoneal malignant ascites is a major cause of morbidity and mortality.

The radical-ionic coupling of chloropyrazine-2-carboxylic acid derivatives with methoxybenzenethiols, carried out in the presence of a heterogeneous copper catalyst, provided the series of 6- or 5- or 3-(4-methoxyphenyl)sulfanylpyrazine- 2-carboxylic acid derivatives as well as 6- or 5- or 3-(3-methoxyphenyl)sulfanylpyrazine-2-carboxylic acid derivatives. The prepared compounds were evaluated as potential antifungal agents and new antituberculotics. Their preliminary in vitro evaluation of antimycobacterial activity according to the international program with the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) is presented. Several compounds showed an interesting activity in the preliminary screening with a percentage growth inhibition of the virulent Mycobacterium tuberculosis H37Rv between 50 to 100% at the concentration 6.25 μg/mL. Structure-activity relationships among the chemical structure, the physical properties and the biological activities of the evaluated compounds are discussed in the article.

Objective: Selenium (Se) in the form of selenocysteine is an essential component of the family of the detoxifying enzymes glutathione peroxidase (Gpx) and of the iodothyronine selenodeiodinases that catalyze the extrathyroidal production of tri-iodothyronine (T(3)). Thus, Se deficiency may seriously influence the generation of free radicals, the conversion of thyroxine (T(4)) to T(3) and a thyroidal autoimmune process. The aim of this study was to investigate whether serum Se levels may influence the outcome of Graves' disease (GD). Design And Methods: 83 patients (77 women, 6 men) with active GD were retrospectively analyzed (mean age 40,0 years). Twenty-four GD patients went into remission and were euthyroid during follow-up (median follow-up: 20.1 months), whereas 59 patients did not go into remission or developed relapse over the following 24 months. TSH receptor autoantibodies (TRAb) were measured using the second generation assay on the basis of human TSH receptor. Se levels were determined at the first visit in our outpatient clinic and were correlated with TRAb levels and clinical outcome of these patients. Results: Median TRAb levels in the group of remission were significantly (p<0.0001) lower than TRAb values in the relapse group (2.1 as compared to 8.6 IU/l). By comparing mean serum Se levels in the remission and relapse group no significant differences were seen (73.0 vs. 71.7 ug/l). Detailed analyses of both groups of patients, however, revealed that highest serum Se levels (>120 ug/l) were seen in the remission group, indicating a positive effect of Se levels on the outcome of GD. In addition, we also compared these results with TRAb levels of these patients. We could show that TRAb levels and serum Se values were positively correlated in the relapse group, whereas a negative correlation of both parameters were seen in the remission group, supporting the idea of a positive effect of Se on thyroidal autoimmune process. Conclusion: Our data indicate that high serum Se levels (>120 ug/l) may influence the outcome of GD. This is important, as Se administration trials in GD, which are under discussion need to be performed with Se supplementation at higher dosages than used in autoimmune thyroiditis.

Substantial evidence indicates that neuroactive kynurenine metabolites play a role in the normal physiology of the human brain, and are involved in the pathology of neurodegenerative disorders such as Parkinson's disease and Huntington's disease. A side-arm product of the pathway, kynurenic acid (KYNA), which is synthesized by the irreversible transamination of kynurenine (KYN) by kynurenine aminotransferases (KAT I and KAT II), is an excitatory amino acid receptor antagonist. In the present study, we measured the level of KYNA and the activities of the biosynthetic enzyme isoforms KAT I and KAT II in the plasma and in the erythrocytes (RBCs) of patients with cervical dystonia or blepharospasm and in age-matched controls. The KAT I and KAT II activities were significantly lower in the plasma of the patients in both subgroups. In the RBCs, only the KAT I activity was elevated significantly. The KYNA concentration was unchanged in both type of patients. These data support the contribution of an altered kynurenine metabolism to the pathogenesis of focal dystonia.

β-Thalassemia patients suffer from secondary iron overload caused by increased iron absorption and multiple blood transfusions. Excessive iron catalyzes free-radical formation, causing oxidative tissue damage. Non-transferrin bound iron (NTBI) detected in thalassemic plasma is highly toxic and chelatable. Desferrioxamine and deferiprone are used to treat the iron overload, but many side effects are found. Epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) in green tea (GT) show strong antioxidant properties. We separated the EGCG and ECG from GT extract using an HPLC, and examined their iron-binding and free-radical scavenging activities. They bound Fe3+ rapidly to form a complex with a predominant absorption at 560 nm. EGCG and ECG bound chemical Fe3+ and chelated the NTBI in a time- and dose dependent manner. They also decreased oxidative stress in iron-treated erythrocytes. In conclusion, EGCG and ECG could be natural iron chelators that efficiently decrease the levels of NTBI and free radicals in iron overload.

Redistribution of redox-active divalent metal ions (e.g. copper, zinc, and iron) in postmitotic tissues of lipoic acid supplemented aging rats has been proposed to contribute to metal-catalyzed protein oxidation. DL-alpha lipoic acid (LA) (100 mg/kg body wt/day) was administered intraperitoneally to the Sprague-Dawley rats for 14 days. Serum copper levels lowered in the aged rats with LA supplementation compared to the rats without LA supplementation. On the other hand, serum zinc and iron levels increased in the aged rats with LA supplementation compared to the rats without LA supplementation. Copper levels of the postmitotic tissues were not changed in the aged rats with LA supplementation compared to the controls. The heart zinc levels detected in LA supplemented rats were significantly lower than controls. Similarly, the iron levels of the heart were found to be significantly lower in LA supplemented rats when compared to control rats. LA supplementation did not affect brain and muscle iron levels. The brain and muscle zinc levels remained the same in both group of rats. Based on the findings of our study, we have concluded that LA may exhibit prooxidant effect depending on the altered trace element homeostasis. Therefore, our results emphasize the importance of monitoring the dose of LA supplementation, duration of treatment and its potential harmful effects in the postmitotic tissues of aged rats.

The last 10 years have seen resurgent industry activity in discovery and development of new drugs for the treatment of tuberculosis (TB), a growing widespread and devastating (more than 2 million deaths annually) bacterial infection that is of increasing concern in developing and developed nations alike. This review describes drugs currently being evaluated in the clinic for treatment of uncomplicated and drug resistant pulmonary TB, and updates the literature on 5 new drugs that entered clinical trials in the last 4 years.