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  • Open access
  • 16 Reads
Interaction of Zinc(II) and Copper(II) Terpyridine Complexes with Biomolecules
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Transition metal ions exhibit a unique role in diverse biological activities of proteins by acting as cofactors. In particular, zinc and copper ions modulate enzymes activities as well as many catalytic and oxidative/reductive processes. The kinetics and mechanism of the substitution reactions of dichloro [ZnCl2(terpy)] and [CuCl2(terpy)]  (terpy = 2,2′:6′,2′′-terpyridine) with biologically relevant ligands have been studied as a function of nucleophile concentrations at pH 7.38, under pseudo-first-order condition by UV-Vis spectrophotometric techniques. The interactions of Cu(II) and Zn(II) complexes with tripeptide glutathione (GSH) were investigated under pseudo-first-order conditions with respect to the complex concentration. For the substitution process of Zn(II) complex with glutathione (GSH), pre-equilibrium and chelate formation have been noted. The [CuCl2(terpy)] is more reactive than [ZnCl2(terpy)] complex and the second-order rate constants for the first step follow the order of reactivity: GSH > DL-Asp > L -Met > 5’-GMP ~ 5’-IMP for Cu(II)  complex,  while for Zn(II) the order of reactivity is: DL-Asp >  L -Met > GSH ~  5’-GMP > 5’-IMP. The results are discussed in terms of mechanisms of interactions between metalloproteins and biomolecules.

  • Open access
  • 23 Reads
Antibacterial Activity of Zinc(II) and Copper(II) Terpyridine Complexes
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Zinc(ll) and copper(II) complexes with organic molecules are used in clinical medicine, e.g. (i) complex of zinc(ll) acetate with erythromycin is used for ache therapy, (ii) copper chelating agents were developed to treat Wilson disease, an autosomal recessive genetic disorder that causes copper accumulation primarily in the liver. In general, organic ligands can contribute to better transport of metal ions through the lipophillic regions of cell membranes. However, it is also possible that some metal complexes are not able to reach their site of action in sufficient concentration due to their decreased solubility. Antibacterial activity of model  [ZnCl2(terpy)]  and  [CuCl2(terpy)] complexes  was tested against seven strains of bacteria. The complexes were more effective against Gram-positive than Gram-negative bacteria. Between complexes, stronger effect was observed for [CuCl2(terpy)] complex. The best effect was exhibited against Sarcina lutea (5 mg/ml). Escherichia coli showed low sensitivity to both complexes. Results of the study of the antibacterial activity suggest an absence of permeability of the complexes through the membrane proteins.  

  • Open access
  • 21 Reads
In vitro Anti-leishmanial and Anti-trypanosomal Activity of Hydrazones, Pyrazoles, Pyrazolo[1,5-a]pyrimidines and Pyrazolo[3,4-b]pyridines Synthesized from 6-Substituted-3-formylchromones
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Between the functionalized chromones, 3-formylchromone is a highly reactive synthon used in many reactions due to the presence of electron-deficient centers at C-2, C-4 and the C-3 formyl group. Reaction of the -CHO group with nitrogen nucleophiles such as hydrazine and aminopyrazole derivatives has led to the formation of a variety of molecules that have been studied in detail for being of interest to drug discovery. Chromone-3-carboxaldehydes react with aromatic primary hydrazines mainly at the formyl group by a straightforward 1,2-addition to form the corresponding hydrazone, but when the reaction is submitted to prolonged heating, a pyrazole-type structure is produced by a 1,4-addition reaction accompanied by pyrone ring-opening followed by recyclization and proton transfer. On the other hand, reaction of 3-formylchromone with equimolar quantities of aminopyrazole derivatives was shown to afford mainly pyrazolo[1,5-a]-pyrimidines, formed by the above-mentioned cyclization process of an imine intermediate.

Led by the biological and pharmacological relevance of the 3-formylchromone derivatives and its interesting chemistry, in this work we present the synthesis of a series of pyrazoles (4a-c), hydrazones (5a-c), pyrazolo[1,5-a]-pyrimidines (6a, 6b) and one pyrazolo[3,4-b]-pyridine (7) and the report on their in vitro anti-leishmanial and anti-trypanosomal activity. Chemical results showed that the formation of regioisomer 7 may arise from an imine intermediary that undergoes 1,4-addition at C-2 by attack of C-4' from the pyrazole instead of the nitrogen atom N-2'. To the best of our knowledge, this is the first report regarding formation of pyrazolo[3,4-b]-pyridines by intramolecular attack of an sp2 carbon atom.

The in vitro studies were performed against strains of Leishmania mexicana (bel 21) and Tripanosoma cruzi (DM28). Compounds 5a and 5b showed activity at micromolar level and good selectivity index (SI) with IC50 values of 6.3 (SI = 3.4) and 15 (SI = 1.9) mM for L. Mexicana and 4.1 (SI = 5.2) and 10 (SI = 3) mM for T. cruzi respectively. From the above-mentioned results, compounds 5a and 5b may be considered for further chemical modifications in order to increase their activity as potential antiparasitic agents.

  • Open access
  • 17 Reads
Bioprospecting of Asteraceae Medicinal Plants of Pakistan for their Associated Bioactive Endophytic Actinomycetes for New Drug Targets
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Since the beginning of mankind, plants have been used as the source of medicinal agents thereby becoming a major course to discovering new drugs. The practice of using traditional medicine is prevalent in Pakistan that has a rich history of herbal plants being used by Hakims in folk medicine (Unani medicine). The Asteraceae family is the largest plant family in Pakistan, with plants of considerable medicinal importance. Endophytes include all organisms that symptomless colonize the living internal tissues of their hosts during a variable period of their lifetime. There they produce a broad variety of bioactive secondary metabolites with unique structure that are advantageous for the plant. Endophytic actinomycetes also colonize the internal tissues of plants without causing any visible changes or damage. They exploit an unusual habitat and considering this, this may enable them to possess the potential to produce bioactive compounds as similar to their host plant. Our study explores the bioprospecting potential related to endophytic actinomycetes of Asteraceae medicinal plants of Pakistan. After isolation and identification the endophytes were screened for their bioactive metabolites potential for new drug targets. This included extensive biological and chemical screening. The bioactive compounds were purified by column chromatography and final identification was done through HPLC-MS and NMR. The purified compounds were observed to be extremely potent with promising antimicrobial potential against major pathogens including algae and fungal strains as well as posessing antioxidant and cytotoxic potential.       

  • Open access
  • 20 Reads
In Vitro Cytotoxic Evaluation of New indolo-Triterpene Derivatives, Synthesized from Serjanic Acid
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Pentacyclic triterpenes represent a very promising and expansive platform for bioactive natural products. Its potential has begun to be exploited by the pharmaceutical industry. The study of these secondary metabolites has been focused mainly in evaluating their activity as potential anti-viral and anti-cancer agents, and in most cases, the increase of the activity is closely related to the chemical modification of the hydroxyl or carboxyl group located at positions C-3 and/or C-28 of the molecule. At present, most of the research on the chemical modification of triterpenes involves the insertion of heterocyclic rings, either through covalent bonds or by ring fusion. 

Serjanic acid (1) is a natural pentacyclic triterpene found in the fruits of the plant Phytolacca icosandra (Phytolaccaceae). Despite the structural similarities of this compound with other bioactive triterpenes such as oleanolic, boswellic and moronic acids, there are almost no studies on the chemical modification of this acid. Due to this, and based on the biological and pharmacological potential that this compounds might have, in this study we carried out the synthesis, structural characterization and cytotoxic evaluation of six new indolo-triterpene derivatives (813) from the natural triterpenoid serjanic acid (1). The compounds were synthesized via indolization reactions between the ketones 2 and phenylhydrazines 37 and their structures elucidated by IR, 1H-NMR, 13C-NMR and HR-MS techniques as: indolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (8), 5-bromoindolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (9), 7-bromo-indolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (10), 4-bromo-indolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (11), 6-bromo-indolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (12) and 4,7-dichloro-indolo[2,3-b]olean-12-en-28,30-dioic acid-30-methyl ester (13). All compounds were tested trough the brine shrimp lethality assay to determinate their potential as cytotoxic agents. LC50 values of the new synthesized compounds were between 28.6 and 78.8 micromolar.

  • Open access
  • 20 Reads
Evaluation of the Utility of the Rubiatriol Scaffold as Lead in Angiotensin Converting Enzyme Modulation for the Management of Hypertension
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Introduction: Angiotensin Converting Enzyme (ACE), a key enzyme in Renin Angiotensin System for production of angiotensin II and a mediator for hypertension, is a target for cardiovascular disease management. Arisawa et al. claim that the naturally occurring triterpene Rubiatriol, has ACE-inhibitory activity. This study aimed to, using Rubiatriol as lead molecule, validate this hypothesis using in silico techniques and to design novel high affinity structures for the ACE using de novo methods.

Methodology: Protein Databank crystallographic deposition 2C6N describing the ACE:Lisinopril complex, was selected as a template. Binding affinity of Lisinopril for the ACE was calculated using X-Score. Rubiatriol was docked into the ACE_Ligand Binding Pocket (LBP), and conformational analysis performed. Structure activity relationship data and 2D topology maps generated in Poseview highlighting the interactions of the optimal conformer with the LBP amino acids, guided the creation of five seed structures onto which novel growth was sustained within the ACE ligand binding pocket using the GROW module of LigBuilderv1.2. The generated molecular cohort was assessed for Lipinski Rule compliance.

Results:  The Lipinski rule compliant molecular cohort was, for each seed, segregated into families of similar pharmacophoric structure, and ranked according to binding affinity and physicochemical parameter. The highest ranking molecules were identified for optimisation and in vitro validation.

Discussion: This study is valuable for validation of the hypothesis of Arisawa et al. using in silico methods, and for suggesting that the rubiatriol scaffold was a suitable lead for the generation of ACE modulating molecules with a binding affinity superior to that of Lisinopril.

  • Open access
  • 32 Reads
N-Farnesyl-norcantharimide Inhibits Progression of Human Leukemic Jurkat T Cells Through Up-regulation of Tumor Suppressor Gene and Down-regulation of Steroid Biosynthesis, Metabolic Pathways, and Fatty Acid Metabolism
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

Background: N-farnesyl-norcantharimide (C23H33NO3, designated as NC15) is a norcantharidin derivative with high anti-cancer activity in cell and syngeneic mouse models. However, the anti-cancer mechanism of NC15 is not clear.

Methods: The cell viability of human leukemic Jurkat T (JKT) cells after treatment with NC15 was assessed using cell counting Kit-8 method. The IC50 of NC15-treated JKT cells was estimated using dose–response curve. Flow cytometry analysis, human apoptosis antibody array assay, and whole genome sequencing were performed to investigate the anti-cancer mechanism of NC15 in JKT cells.

Results: The IC50 of NC15 in JKT cells at 24 and 48 h was 2.51 and 2.54 μmol/ml, respectively. The inhibition rates of cell viability were about 80% and 95% when the cells were treated with 8 μmol/ml NC15 for 24 and 48 h, respectively. The percentages of NC15-treated cells in the sub-G1 phase at 24 and 48 h were 22.0% and 34.3 %, respectively, in contrast to the 1.5% in the control. NC15 could not induce apoptosis in JKT cells. Whole genome sequencing of NC15-treated JKT cells showed that many tumor suppressor genes (TSG) were up-regulated, while many genes for steroid biosynthesis, metabolic pathways, and fatty acid metabolism were down-regulated.

Conclusions: The NC15 can reduce the cell viability and increase the percentage of cells in the sub-G1 phase. The NC15 might inhibit progression of JKT cells through the up-regulation of TSG and the down-regulation of steroid biosynthesis, metabolic pathways, and fatty acid metabolism, instead of through apoptosis.

  • Open access
  • 27 Reads
Artemisinin: Tentative Mechanism of Action and Resistance
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

The sesquiterpene lactones constitute a large class of secondary plant metabolites, which carry a‑methylene‑g‑lactone groups as common structural element and display a number of bioactivities. Every year, 1–2 million people living in the tropics and subtropics die of malaria. Lactone artemisinin is the most effective treatment vs. malaria, the most infectious disease in the world today. Artemisinins are derived from extracts of sweet wormwood (Artemisia annua) and are well established for the treatment of malaria, e.g., highly drug-resistant strains. They resulted in one of the most significant advances in the treatment of malaria since the discovery and first use of quinine over 300 years ago. Their efficacy also extends to phylogenetically unrelated parasitic infections, e.g., schistosomiasis. They showed potent and broad anticancer properties in cell lines and animal models. What hope does this drug offer for the future? The pharmacophoric peroxide –O1–O2– linkage in the endoperoxide ring triggers artemisinin to explode. Artemisinin and its derivatives present structures different from the classical quinoline. It is poorly soluble in water (and oil). When creating the first generation of artemisinin derivative drugs in 1970s, the overriding goal was to improve its solubility characteristics, so that artemisinin derivatives be more easily formulated and efficiently delivered. What did it make lactones reach cancer clinical trials? Despite much research, artemisinin remains the only known natural product to contain a 1,2,4‑trioxane ring and A. annua continues to be the only known natural source. Phytochemical investigation of the species revealed an abnormally wide range of other endoperoxides and hydroperoxides, many of which were not tested for their antimalarial activity. It was reported the design, synthesis and cytotoxicity of novel dihydroartemisinin-coumarin hybrids via click chemistry.

  • Open access
  • 23 Reads
Highly Conserved WNV Genomic RNA Domains are Potential Targets of Antiviral RNA Aptamers
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session ECMC-2

West Nile virus (WNV) is an enveloped, single-stranded, positive RNA virus belonging to the Flavivirus genus (Flaviviridae family). Different WNV strains have been involved in important outbreaks of human and animal diseases, and WNV infection is now considered an emerging world health problem. Like other RNA viruses, WNV has a compact RNA genome that efficiently stores all the information required for the completion of the infectious cycle. The efficiency of this storage system is attributable to supracoding elements, i.e., discrete, structural units that play essential functions. The information coded in the form of structural elements overlaps and complements the protein coding information and is highly conserved across Flavivirus spp.  These elements therefore offer interesting potential targets for novel therapeutic agents. We have applied a SELEX procedure to isolate RNA aptamers against the essential 3’ untranslated region (3’UTR) of the WNV genome. Aptamers are oligonucleotides that efficiently and specifically bind to a ligand molecule. Starting from a theoretical highly sequence-variable population consisting of more than 1018 different molecules, and after six rounds of selection we have identified two main groups of aptamers defined by conserved sequence motifs complementary to highly conserved counter parts within essential structural elements of the WNV genome. Current results point out the potential of these essential functional genomic RNA elements to efficiently bind RNA molecules, therefore to be involved in RNA-RNA interactions, offering a potential of being used as targets of antiviral agents based on nucleic acids. Further biochemical and functional studies are being performed to characterize the antiviral activity of identified RNA aptamers.

  • Open access
  • 21 Reads
Clustering of Iron Oxide Nanoparticles into Poly(ethylene oxide)-block-poly(ε-caprolactone) Nanoassemblies as Ultrasensitive MRI Probes
Published: 01 November 2016 by MDPI AG in 2nd International Electronic Conference on Medicinal Chemistry session Posters Session

Recently, polymer vesicles called polymersomes have emerged as promising nanocarriers. Several studies have reported the formation of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) based vesicles due to their high potential for biomedical applications. However, to our knowledge, the incorporation of ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) into these PEO-b-PCL vesicles has not yet been described.

This work reports the self-assemby of PEO2000-b-PCL12650 copolymers with USPIO. PEO2000-b-PCL12650 was chosen as amphiphilic copolymer because PEO block is biocompatible and prolong the circulation time of nanoparticles in vivo whereas PCL block is biodegradable. Moreover, PEO2000-b-PCL12000 copolymers have been reported to form vesicles.

USPIO were synthesized by the thermal decomposition method (magnetic core size of 4.2 nm and 7.5 nm) and self-assembly of PEO2000-b-PCL12650 with USPIO was performed by nanoprecipitation. Polymeric nanoparticles with diameters close to 100 nm and a high USPIO content were formed as shown by dynamic light scattering (DLS), transmission electron microscopy (TEM) and cryo-TEM. These nanoassemblies are characterized by very high r2/r1 ratios (at 20 and 60 MHz) which makes them highly promising canditates as T2-contrast agents for magnetic resonance imaging (MRI). The size of USPIO entrapped in PEO-b-PCL nanoassemblies has a strong impact on their magnetic properties. Indeed it affects both their longitudinal and their transverse relaxivities and thus their magnetic resonance imaging (MRI) sensitivity.

The next steps in further studies will be the incorporation of an anti-cancer drug into these nanocarriers and the attachment of an active targeting group such as an RGD-containing peptide to their surfaces.

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