Medicinal Chemistry - Volume 4, Issue 3, 2008

A series of quinoxalines variously substituted, namely 3-arylthiomethyl-1,6-dimethylquinoxalin-2-ones (6a-f), 3-arylthiomethyl-1-benzyl-7-trifluoromethylquinoxalin-2-ones (8a-g) and 2-arylthiomethyl-3-benzyloxy-6-trifluoromethylquinoxalines (10a,b,e-h), were synthesized and compared with previous arylphenoxymethylquinoxalines (1a-f, 2af and 3a-b). The purpose was to verify whether the replacement of oxygen with sulphur atom and the insertion of different substituents on the phenyl side chain were able to improve the capability to inhibit the Pgp pump and restore the antiproliferative activity of clinically useful drugs, such as doxorubicin (Doxo), vincristine (VCR) and etoposide (VP16), in drugresistant human nasopharyngeal carcinoma KB cells (KBwt, KBMDR, KB7D and KBV20C). Furthermore, 2,3-bis(aryloxymethyl)- 6-trifluoromethylquinoxalines (13a-c) were designed with the objective to evaluate the capability of the double side chain to potentiate the antiproliferative activity of the drugs tested. Biological assays showed that title compounds were, in general, endowed with good activity as Pgp inhibitors. In particular compound 3a, bearing 2-CONHPh substituent on phenoxymethyl side chain, resulted the most effective, while the double side chain (compound 13c) gives the ability to inhibit a different MRP pump (a membrane glycoprotein named mrp). Furthermore, we can conclude that replacement of oxygen with sulphur atom did not improve the biological activity.

A series of pyrrolidine derivatives were designed and synthesized in good yields starting from commercially available 4-hydroxy-L-proline using a suitable synthetic strategy. And their ability to inhibit neuraminidase was evaluated. These compounds showed potent inhibitory activity against influenza A (H3N2) neuraminidase. Within this series, four compounds, 6e, 9c, 9f and 10e, have the good potency (IC50=1.56∼2.40μM) which is compared to the NA inhibitor oseltamivir (IC50=1.06μM), and could be used as lead compound in the future.

The family of Cyclin-Dependent Kinases (CDKs) can be subdivided into two major functional groups based on their roles in cell cycle and/or transcriptional control. CDK9 is the catalytic subunit of positive transcription elongation factor b (P-TEFb). CDK9 is the kinase of the TAK complex (Tat-associated kinase complex), and binds to Tat protein of HIV, suggesting a possible role for CDK9 in AIDS progression. CDK9 complexed with its regulatory partner cyclin T1, serves as a cellular mediator of the transactivation function of the HIV Tat protein. P-TEFb is responsible for the phosphorylation of the carboxyl-terminal domain of RNA Pol II, resulting in stimulation of transcription. Furthermore, the complexes containing CDK9 induce the differentiation in distinct tissue. The CDK9/cyclin T1 complex is expressed at higher level in more differentiated primary neuroectodermal and neuroblastoma tumors, showing a correlation between the kinase expression and tumor differentiation grade. This may have clinical and therapeutical implications for these tumor types. Among the CDK inhibitors two have shown to be effective against CDK9: Roscovitine and Flavopiridol. These two inhibitors prevented the replication of human immunodeficiency virus (HIV) type 1 by blocking Tat transactivation of the HIV type 1 promoter. These compounds inhibit CDKs by binding to the catalytic domain in place of ATP, preventing transfer of a phosphate group to the substrate. More sensitive therapeutic agents of CDK9 can be designed, and structural studies can add information in the understanding of this kinase. The major features related to CDK9 inhibition will be reviewed in this article.

Arbutus unedo L. has been for a long time employed in traditional and popular medicine as an astringent, diuretic, urinary anti-septic, and more recently, in the therapy of hypertension and diabetes. Signal transducer and activator of transcription 1 (STAT1) is a fascinating and complex protein with multiple yet contrasting transcriptional functions. Although activation of this nuclear factor is finely regulated in order to control the entire inflammatory process, its hyperactivation or time-spatially erroneous activation may lead to exacerbation of inflammation. The modulation of this nuclear factor, therefore, has recently been considered as a new strategy in the treatment of inflammatory diseases. In this study, we present data showing that the aqueous extract of Arbutus unedo's leaves exerts inhibitory action on interferon-γ (IFN- γ)-elicited activation of STAT1, both in human breast cancer cell line MDA-MB-231 and in human fibroblasts. This down-regulation of STAT1 is shown to result from a reduced tyrosine phosphorylation of STAT1 protein. Evidence is also presented indicating that the inhibitory effect of this extract may be mediated through enhancement of tyrosine phosphorylation of SHP2 tyrosine phosphatase. The modulation of this nuclear factor turns out into the regulation of the expression of a number of genes involved in the inflammatory response such as inducible nitric oxide synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1). Taken together, our results suggest that the employment of the Arbutus unedo aqueous extract is promising, at least, as an auxiliary anti-inflammatory treatment of diseases in which STAT1 plays a critical role.

In a systematic effort aimed at identifying new steroidal cytotoxic agents with potent antipoliferative activity against cancer cells and developing their QSAR models, series of 4-nitro, 4-isopropyl, 4-methoxy and 3,4-dimethoxy substituted benzylidene androst-5-ene derivatives were synthesized. The selected compounds were evaluated for antineoplastic activity against a panel of three human cell lines-breast, CNS and lungs at NCI, Bethesda, USA. The results presented herein reports that compounds 7, 9, 10, 15,16, 18, 20-25, 30, 32-36 and 44 have been found to be active anticancer agents. The QSAR of 20 compounds was performed separately for each cell line and best-fit QSAR models are developed. The QSAR models obtained have shown significant correlations (r2 range: 0.9163 to 0.8164) and good predictive performance (q2 range: 0.8499- 0.6320). The validation of models has also been performed using the test set of compounds 5, 15 and 44.

Hydroxamic acids the multifunctional molecules with general formula R'-C(=O)NROH have interesting medicinal and biological potentiality. The antiproliferative activity of 12 hydroxamic acids has been tested in vitro towards human adenocarcinama cell line by MTT assay. The IC50 values were found to be in the range from 12 to 152.8μM. The most potent product identified is N-p-chlorophenyl-4-nitrobenzohydroxamic acid with IC50 value 12μM. The RP-HPLC experiment of these molecules was performed with 50:50V/V% methanol - water mixture as mobile phase. A QSAR is developed for the human adenocarcinoma cells inhibitory activity of a series of hydroxamic acids (n=1-12) that are structurally related to hydroxyurea. Multivariate analytical tool, projection to latent structures was used to develop a suitably predictive model for the purpose of optimizing and identifying members with more potent inhibitory activity. The crossvalidated Q2cum values for two optimal PLS models of hydroxamic acids are above 0.690 (remarkably higher 0.500), indicating good predictive abilities for log1/IC50 values of HAs. By partial least squares regression, two QSAR models revealed that, besides the essential pharmacophore - NOH.C=O, retention capacity factor, logk', polar surface area, PSA, Dipole moment, Dm, total no. of hydrogen bond donor and acceptor atoms, H, and chlorine atoms attached in upper or/and lower phenyl rings, ICl , are important determinants for the inhibitory potency against A431 cells.

Three kinds of β-cyclodextrin derivatives conjugated with glucose moieties, which were expected as models for a drug carrier targeting the drug delivery systems, were designed and synthesized from β-cyclodextrin and the natural product, 4-hydroxyphenyl-β-D-glucopyranoside called arbutin. Arbutin was used because it had a phenyl group with a hydroxyl function which could be used to link the glucose moiety to β-cyclodextrin. The evaluations of these conjugates as the drug-carrying molecules were done by investigating the molecular interactions with the carbohydrate-binding Concanavalin A (Con A) lectin and the anticancer agent, doxorubicin (DXR), using an SPR optical biosensor. The association constants of the conjugates with immobilized Con A were 2.0 x 103 ∼ 8.8 x 103 M-1. The result showed that the Con A bound to the glucose moieties from arbutin in the conjugates with prospective association constants. The inclusion associations of the conjugates with immobilized DXR reached 2.2 x 105 ∼ 1.4 x 108 M-1. The extremely high inclusion associations for DXR suggested their potential abilities as drug-carrying molecules for carrying DXR. The NMR analyses indicated that the phenyl group of the conjugates greatly served to increase the inclusion associations for DXR. In their DXR inclusion complexes, the formation of the stacking complexes by the π-π interactions between the phenyl groups and the included DXR also enhanced their inclusion abilities for DXR.

The neurotrophic factors play an important role in the maintenance of neurone viability and neuronal communication which are considered to be altered in schizophrenia. Subchronic application of ketamine (Ket) was found to be a useful model in schizophrenia research. To further validate this model the mRNA levels of neurotrophic factors NGF, NT- 3, and BDNF and their receptors TrkA, TrkB, and TrkC, respectively, were measured in different brain areas in Ketpretreated rats subchronically dosed with the atypical antipsychotic drug risperidone (Ris). With the exception of NGF in the frontal cortex, Ket pretreatment did change NGF, NT-3, and BDNF mRNA levels in the frontal cortex, the hippocampus, the striatum, the thalamus/hypothalamus region, and in the cerebellum. These changes correspond with changes at their tyrosine kinase receptors. Ris treatment normalised altered NT-3 levels in the hippocampus and balanced BDNF levels in the same structure. It was concluded that the Ket model might reflect distinct alterations in neurotrophic factor activity as found in schizophrenic patients and, moreover, that Ris treatment rebalances disturbed neurotrophic factor activity.

Live Yeast Cell Derivative is a medicinal extract of Saccharomyces cerevisiae that has demonstrated efficacy in improving the rate and quality of wound healing in mouse and human systems. However, the mechanisms by which LYCD promotes healing are largely uncharacterized. In this report, we demonstrate that LYCD has effects on the transcriptional profile of the human monocytic cell line THP-1. Thirty minute exposures of THP-1 cells with LYCD induced a 6 to 44-fold, dose-dependent increase in the relative expression of the proto-oncogene c-fos in complete media containing 10% FBS or in low serum media containing 0.1% FBS. Furthermore, protein levels of c-Fos rise at 30 minutes of LYCD exposure and remained detectable for at least 120 minutes of LYCD exposure. However, the relative abundance of the cfos transcript returned to basal levels by 120 minutes. LYCD also induced expression of c-jun with maximal expression of 3-fold at 60 minutes of exposure. Pretreatments with EGFR kinase inhibitor AG-1478 and the MEK1 inhibitor PD98059 blocked the LYCD-dependent increases in c-fos expression. Consistent with signaling through the EGFR, we have demonstrated by RT-PCR the presence of the mRNA for the EGFR (ErbB1/HER1) in THP-1 cells. Taken together these data suggest that LYCD acts through an EGFR-like cell surface receptor resulting in the activation of the EGFR kinase and the ERK1/2 signaling cascade.

To optimize the physiochemical properties of 2-alkoxydihydrocinnamates as PPARα/γ dual agonist, a quantitative structure activity relationship, Hansch approach was made using combination of various thermodynamic, electronic and spatial descriptors. Several regression expressions are obtained using multiple linear regression analysis. The best QSAR model is further validated by leave-one-out cross validation method. Analyses of results from the present QSAR study suggest that for favorable dual PPARα/γ agonist activity electronic property of the substituents in hydrophobic tail phenyl ring plays a key role. The contribution of Hammett constant and dipole moment in the models deduced the importance of electron withdrawing substituents for dual activity. Additionally the study also indicates that bulky substituents in head acid moiety not confer selectivity towards the PPAR activity. Thus the QSAR study brings important structural insight to aid the design of dual PPARα/γ receptor agonist.

As microbes use many mechanisms for avoiding immunological pressure, new strategies must be developed to bypass the immunological code of silence of conserved, functionally-important amino acid sequences, such as those involved in high activity binding peptides' (HABPs) attaching to their host cells. Hundreds of experiments in large numbers of Aotus monkeys revealed that this immunological code of silence could be broken by shifting the polarity of some critical host cell binding residues in these HABPs by substituting F for R and vice versa, Y↔W, L↔H, I↔N, P↔D, M↔K or E, C↔T, V↔N or S; there are special rules for A, G and S. 1H-nuclear magnetic resonance of these modified, immunogenic, protection-inducing HABPs and molecular modelling revealed that such modifications induced appropriate fitting into specific HLA-DRβ1* Pockets, suggesting the presence of new pockets and a haplotype- and allele-specific conscious TCR. A highly immunogenic and protection-inducing anti-malarial vaccine can thus be produced.

Several studies in humans and laboratory animals with type 2 diabetes indicate that antioxidant supplements lessen the impact of oxidative damage caused by dysregulation of glucose metabolism. The present study was undertaken to examine the effect of soybean oil on glycaemic control and lipid metabolism in Goto-kakizaki (GK) rats, a model of type 2 diabetes. Rats were divided into three groups, a control group of non-diabetic (Wistar) rats, a group of diabetic GK rats and a group of GK rats treated with soybean oil. Plasma samples from the different groups were analysed for total α- tocopherol, coenzyme Q and glucose levels. Glycated haemoglobin was also compared between the different groups. Fasting and non-fasting blood glucose levels were significantly decreased in soybean oil group compared with GK group. There was also a 14 % reduction in the levels of HbA1c in SO-treated GK when compared with the diabetic control group. Diabetes induced a decrease in coenzyme Q plasma levels that prevailed after treatment with soybean oil. Moreover, the plasma α-tocopherol levels were higher after treatment with soybean oil. Conclusions: Our observations suggest that soybean oil treatment may be beneficial in type 2 diabetes. Since soybean oil has very high amounts of coenzyme Q and other antioxidants one possible mechanism of action could be as an antioxidant.