Medicinal Chemistry - Volume 11, Issue 1, 2015

Background: Cholesterol, derived from two different sources of endogenous synthesis and diet, is essential for the growth and maintenance of mammalian cells. However, elevated level of serum cholesterol is among the associated risk factors for the coronary heart disease. Statins can reduce endogenous sterol synthesis by inhibiting HMG-CoA reductase, whereas cholesterol absorption inhibitors, such as ezetimibe, can block cholesterol uptake from dietary sources by blocking Niemann- Pick C1-like 1 (NPC1L1). Objective: The present review focuses on the main research progress of cholesterol absorption inhibitors, the structure of NPC1L1 and discovery of novel chemical entities by virtual screening. Conclusion: Studies on the structure-activity relationship reveal that azetidinone is important to maintain activity in azetidinone derivatives and the novel heterocyclic compounds with replacement of β-lactam scaffold by oxazolidinone also show similar activity as ezetimibe. Moreover, virtual screening is a computer-aided molecular design tool to propose novel cholesterol absorption inhibitors.

Derivatives of quinoxalinedione (QX) were chosen as chemical lead for the development of new radioligands of the AMPA receptor, since there are several examples of QX-derivatives with high affinity. The radiosyntheses of the new compounds 6-[18F]fluoro-7-nitro-QX ([18F]FNQX) and 7-[18F]fluoro-6-cyano-QX ([18F]FCQX) with radiochemical yields of 8 ± 2 and 3 ± 2 %, respectively, as well as the evaluation of their binding properties to the AMPA-receptor were performed. A comparison of the Ki-values of the new QX-derivatives FCQX and FNQX with mono-substituted cyanoand nitro-QX shows negligibly small differences of affinity (within the range of 1.4 to 5 µM), but exhibits a tenfold lower affinity than derivatives with two electron withdrawing groups like the 7-cyano-6-nitro-compound CNQX and the 6,7- dinitro compound DNQX. Thus, with respect to the low affinity and a high non-specific binding with in vitro and ex vivo autoradiographic studies, the new compounds do not lend themselves for in vivo imaging.

This paper describes preparation and in vitro evaluation of 19 compounds related to the selective experimental cholinesterase inhibitor BW284c51. The novel compounds were prepared as fragments of parent molecule BW284c51 and evaluated on the model of human recombinant acetylcholinesterase and human plasmatic butyrylcholinesterase. The IC50 values of the prepared compounds were compared to the parent molecule BW284c51. None of the compounds was superior to the parent drug, but two BW284c51 fragments showed promising hAChE inhibition in µM scale and improved selectivity. These two fragments were further subjected to the molecular modelling study and their enzyme interactions were rationalized. The structure-activity relationship of the prepared series was stated.

Valproic acid (VPA) is considered first-line drug in treatment of generalized idiopathic seizures such as absence, generalized tonic-clonic and myoclonic seizures. Among major antiepileptic drugs, VPA is also considered effective in childhood epilepsies and infantile spasms. Due to its broad activity, VPA acts as a mood stabilizer in bipolar disorder and it is useful in migraine prophylaxis. Despite its long-standing usage, severe reactions to VPA, such as liver toxicity and teratogenicity, are reported. To circumvent side effects due to structural characteristics of VPA, we synthesized in good yield a new VPA-aminoacid conjugate, the N-valproyl-L-Phenylalanine, and characterized by FT-IR, MS, 13C and 1H- NMR analyses. The Log DpH7.4 value (0.19) indicated that new molecule was potentially able to cross biological membranes. The resistance to chemical and enzymatic hydrolysis of N-valproyl-L-phenylalanine was also assessed. All trials suggested that the compound, at the pH conditions of the entire gastro-intestinal tract, remained unmodified. Furthermore, the new compound did not undergo enzymatic cleavage both in plasma and in cerebral medium up to 24 h. The toxicity assay on primary cultures of astrocytes indicated that the synthetized conjugate was less toxic than both free VPA and L-Phenylalanine. In this paper, the anticonvulsant activity of the new compound against epileptic burst discharges evoked in vitro in rat hippocampal slices was also evaluated. These preliminary results underline that N-valproyl-L-phenylalanine as new potential antiepileptic agent could represent a good candidate to further investigations.

In this study, 12 new oxime ether derivatives, which were expected to show anticonvulsant and antimicrobial activities, were synthesized. Oxime ether derivatives were synthesized by the reaction of various alkyl halides with 1-(2- naphthyl)-2-(pyrazol-1-yl)ethanone oxime. Anticonvulsant activity of the compounds was determined by maximal electroshock (MES) and subcutaneous metrazol (ScM) seizure tests, while neurological disorders were evaluated using rotorod toxicity test according to the ASP of NIH. Compound 1, 6 and 7 showed anticonvulsant activity at 300 mg/kg dose at 4 h, but compounds 1 and 7 showed toxicity at 300 mg/kg dose at half an hour. Antimicrobial activities of the compounds were also determined using agar microdilution method. Compound 1 and 5 were found to have the highest antifungal activity among the other compounds.

Corticotropin-releasing factor (CRF) is a neurohormone that plays a crucial role in integrating the body’s overall response to stress. It appears necessary and sufficient for the organism to mount functional, physiological and endocrine responses to stressors. CRF is released in response to various triggers such as chronic stress. The role of CRF and its involvement in these neurological disorders suggest that new drugs that can target the CRF function or bind to its receptors may represent a new development of neuropsychiatric medicines to treat various stress-related disorders including depression, anxiety and addictive disorders. Based on pharmacophore of the CRF1 receptor antagonists, a new series of thiazolo[4,5-d] pyrimidines were synthesized as Corticotropin-releasing factor (CRF) receptor modulators and the prepared compounds carry groups shown to produce optimum binding affinity to CRF receptors. Twenty two compounds were evaluated for their CRF1 receptor binding affinity in HEK 293 cell lines and two compounds 5o and 5s showed approximately 25% binding affinity to CRF1 receptors. Selected compounds (5c and 5f) were also evaluated for their effect on expression of genes associated with depression and anxiety disorders such as CRF1, CREB1, MAO-A, SERT, NPY, DatSLC6a3, and DBH and significant upregulation of CRF1 mRNA has been observed with compound 5c.

We report here a new class of compounds, quinoline derivatives, as potential inhibitors of in vitro bovine serum albumin-methylglyoxal glycation. Among compounds 1-19, compound 14 was found to be the most active analog with IC50 of 282.98 ± 8.4 µM. Compounds 12 (IC50 = 661.78 ± 8.7 µM) and 15 (IC50 = 629.43 ± 7.85 7 µM) were also identified as modest inhibitors, in comparison to the standard inhibitor, rutin (IC50 = 294.50 ± 1.5 µM). When evaluated for antioxidant activity through in vitro DPPH radical scavenging assay, compounds 3 (IC50 = 2.19 ± 0.27 µM), 6 (IC50 = 7.35 ± 2.27 µM), 11 (IC50 = 8.96 ± 0.56 µM), and 12 (IC50 = 10.11 ± 2.03 µM), and 15 (IC50 = 7.01 ± 3.87 µM) were found to be more active than the standard i.e. gallic acid (IC50 = 23.34 ± 0.43 µM). These compounds were also evaluated for cytotoxicity against rat fibroblast cell line (3T3 cell line). All compounds were found to be non-toxic in cellular model. This study identifies quinoline derivatives as a new class of inhibitors of protein glycation in vitro, along with antioxidant and non-toxic nature. These properties make them interesting leads for further studies as potential anti-diabetic agents.

In this study, the synthesis, anti-inflammatory and analgesic activities of eight new 5-thioalkyl-1,3-diaryl-1,2,4- triazole derivatives were reported. For the anti-inflammatory study, the carrageenan-induced rat paw edema model was used. The test compounds in 50 mg/kg and 100 mg/kg were injected as IP and paw edema was determined. The results showed that some of the compounds have good activity compared to the references drug, indomethacin. For analgesic activity, the test compounds were studied using the in Tail-flick test model in 50 and 100 mg/kg as IP injections. Their analgesic activities were determined after 30 min via latency time assay. Statistical analysis showed that all test compounds have antinociceptive activity in the range of 24% -47% as compared to the control with a dose of 50 mg/kg. However, all tested compounds have analgesic activity lower than the standard drug, morphine.

That the implementation of Electronic-Topological Method and a variant of Feed Forward Neural Network (FFNN) called as the Associative Neural Network are applied to the compounds of Hydrazones derivatives have been employed in order to construct model which can be used in the prediction of antituberculosis activity. The supervised learning has been performed using (ASNN) and categorized correctly 84.4% of them, namely, 38 out of 45. Ph1 pharmacophore and Ph2 pharmacophore consisting of 6 and 7 atoms, respectively were found. Anti-pharmacophore features socalled “break of activity” have also been revealed, which means that APh1 is found in 22 inactive molecules. Statistical analyses have been carried out by using the descriptors, such as EHOMO, ELUMO, ΔE, hardness, softness, chemical potential, electrophilicity index, exact polarizibility, total of electronic and zero point energies, dipole moment as independent variables in order to account for the dependent variable called inhibition efficiency. Observing several complexities, namely, linearity, nonlinearity and multi-co linearity at the same time leads data to be modeled using two different techniques called multiple regression and Artificial Neural Networks (ANNs) after computing correlations among descriptors in order to compute QSAR. Computations resulting in determining some compounds with relatively high values of inhibition are presented.

Ever growing resistance of pathogenic bacteria against the existing antibiotics has forced researchers to look for new methods and techniques to design effective antimicrobial agents. In the present study a new tetracycline-based antimicrobial polymer (AMP) was synthesized from tetracycline and methacrylic acid (MAAc) using lipase as catalyst. The AMP, thus obtained, was transformed into nanoparticles via an emulsion method. The AMP and its nano-form were characterized by FTIR, NMR, XRD, SEM and EDAX. The antibacterial activity of the AMP was studied against both resistant (-) [P. aeruginosa] and susceptible (+) [S. aureus] bacteria. The synthesized AMP, including its nanoform, was observed to be more potent and efficient antimicrobial agent than the precursor tetracycline.

The present study evaluated the levels of total phenolics, flavonoids, tannins and anthocyanins from Peganum harmala L. seeds and determined their antioxidant, antiplasmodial and anticancer potentials. Antioxidant activity was determined by DPPH and ABTS assays. Extracts of P. harmala seeds from Oudref and Djerba (two places in Tunisia) were obtained by successive extraction solvents: petroleum ether, chloroform, ethyl acetate, ethanol and water. Their composition was evaluated for phenolics (gallic acid equivalent 2.48 to 72.52 g/kg), tannins (catechin equivalent 0 to 25.27 g/kg), anthocyanins (cyanidin equivalent 0 to 20.56 mg/kg) and flavonoids (quercetin equivalent 0 to 3.12 g/kg). Ethanolic extract exerted the highest activities against a chloroquine-resistant strain of Plasmodium falciparum (IC50=23 mg/L), against human breast cancer cells MCF7 (IC50=32 mg/L) and against free radical (IC50=19.09±3.07 mg/L). Correlations were studied between each chemical family and the three activities. Total phenolics content exhibited the highest correlation with antiplasmodial activity (R2=0.92) and with anticancer activity (R2=0.86), respectively.