Edeildo F. da Silva-Júnior

Interaction of β-Carbolines with DNA: Spectroscopic Studies, Correlation with Biological Activity and Molecular Docking

Quantitative interaction of twelve β-carboline derivatives with calf thymus deoxyribonucleic acid (ctDNA) using spectroscopic techniques was evaluated. The values of the binding constants (Kb) obtained for the complexes formed with the ctDNA ranged from 3.30 × 102 to 1.82 × 106 mol L−1, being the β-carbolines with the N,N-dimethylaminophenyl group at position 1 the ones which presented the highest Kb values. The binding mode between the β-carbolines evaluated and ctDNA was proposed from the KI assay, competition with ethidium bromide, and DNA thermal denaturation profile (Tm), where it was possible to infer that the evaluated alkaloids interact with ctDNA preferably via intercalation. Additionally, the correlation of Kb values obtained with the IC50 of seven human cancer cell lines was carried out. From this study, it was possible to observe a linear relation among most of the evaluated derivatives, obtaining r2 values from 0.5360 to 0.9600. In addition, in silico molecular docking was performed to corroborate the experimental results.

Design, synthesis, molecular docking and biological evaluation of thiophen-2-iminothiazolidine derivatives for use against Trypanosoma cruzi

In this study, we designed and synthesized a series of thiophen-2-iminothiazolidine derivatives from thiophen-2-thioureic with good anti-Trypanosoma cruzi activity. Several of the final compounds displayed remarkable trypanocidal activity. The ability of the new compounds to inhibit the activity of the enzyme cruzain, the major cysteine protease of T. cruzi, was also explored. The compounds 3b, 4b, 8b and 8c were the most active derivatives against amastigote form, with significant IC50 values between 9.7 and 6.03μM. The 8c derivative showed the highest potency against cruzain (IC50=2.4μM). Molecular docking study showed that this compound can interact with subsites S1 and S2 simultaneously, and the negative values for the theoretical energy binding (Eb=-7.39kcal·mol(-1)) indicates interaction (via dipole-dipole) between the hybridized sulfur sp(3) atom at the thiazolidine ring and Gly66. Finally, the results suggest that the thiophen-2-iminothiazolidines synthesized are important lead compounds for the continuing battle against Chagas disease.

Preliminary in vitro evaluation of the anti-proliferative activity of guanylhydrazone derivatives.

Abstract Guanylhydrazones have shown promising antitumor activity in preclinical tumor models in several studies. In this study, we aimed at evaluating the cytotoxic effect of a series of synthetic guanylhydrazones. Different human tumor cell lines, by including HCT-8 (colon carcinoma), MDA-MB-435 (melanoma) and SF-295 (glioblastoma) were continuous exposed to guanylhydrazone derivatives for 72 hours and growth inhibition of tumor cell lines and macrophages J774 was measured using tetrazolium salt (MTT) assay. Compounds 7, 11, 16 and 17 showed strong cytotoxic activity with IC50 values lower than 10 μmol L−1 against four tumor cell lines. Among them, 7 was less toxic to non-tumor cells. Finally, obtained data suggest that guanylhydrazones may be regarded as potential lead compounds for the design of novel anticancer agents.

Development and Validation of HPLC-DAD and UHPLC-DAD Methods for the Simultaneous Determination of Guanylhydrazone Derivatives Employing a Factorial Design

Guanylhydrazones are molecules with great pharmacological potential in various therapeutic areas, including antitumoral activity. Factorial design is an excellent tool in the optimization of a chromatographic method, because it is possible quickly change factors such as temperature, mobile phase composition, mobile phase pH, column length, among others to establish the optimal conditions of analysis. The aim of the present work was to develop and validate a HPLC and UHPLC methods for the simultaneous determination of guanylhydrazones with anticancer activity employing experimental design. Precise, exact, linear and robust HPLC and UHPLC methods were developed and validated for the simultaneous quantification of the guanylhydrazones LQM10, LQM14, and LQM17. The UHPLC method was more economic, with a four times less solvent consumption, and 20 times less injection volume, what allowed better column performance. Comparing the empirical approach employed in the HPLC method development to the DoE approach employed in the UHPLC method development, we can conclude that the factorial design made the method development faster, more practical and rational. This resulted in methods that can be employed in the analysis, evaluation and quality control of these new synthetic guanylhydrazones.

Annonalide and derivatives: Semisynthesis, cytotoxic activities and studies on interaction of annonalide with DNA

The cytotoxic activity of the pimarane diterpene annonalide (1) and nine of its semisynthetic derivatives (2-10) was investigated against the human tumor cell lines HL-60 (leukemia), PC-3 (prostate adenocarcinoma), HepG2 (hepatocellular carcinoma), SF-295 (glioblastoma) and HCT-116 (colon cancer), and normal mouse fibroblast (L929) cells. The preparation of 2-10 involved derivatization of the side chain of 1 at C-13. Except for 2, all derivatives are being reported for the first time. Most of the tested compounds presented IC50s below 4.0 μM, being considered potential antitumor agents. The structures of all new compounds were elucidated by spectroscopic analyses including 2D NMR and HRMS. Additionally, the interaction of annonalide (1) with ctDNA was evaluated using spectroscopic techniques, and the formation of a supramolecular complex with the macromolecule was confirmed. Competition assays with fluorescent probes (Hoechst and ethidium bromide) and theoretical studies confirmed that 1 interacts preferentially via DNA intercalation with stoichiometric ratio of 1:1 (1:ctDNA). The ΔG value was calculated as -28.24 kJ mol-1, and indicated that the interaction process occurs spontaneously. Docking studies revealed that van der Walls is the most important interaction in 1-DNA and EB-DNA complexes, and that both ligands (1 and EB) interact with the same DNA residues (DA6, DA17 and DT19).

Highly functionalized piperidines: Free radical scavenging, anticancer activity, DNA interaction and correlation with biological activity

Graphical abstract

The medicinal chemistry of Chikungunya virus

Abstract Arthropod-borne viruses (arboviruses) are an important threat to human and animal health globally. Among these, zoonotic diseases account for billions of cases of human illness and millions of deaths every year, representing an increasing public health problem. Chikungunya virus belongs to the genus Alphavirus of the family Togariridae, and is transmitted mainly by the bite of female mosquitoes of the Aedes aegypti and/or A. albopictus species. The focus of this review will be on the medicinal chemistry of Chikungunya virus, including synthetic and natural products, as well as rationally designed compounds.

Inclusion complex between β-cyclodextrin and hecogenin acetate produces superior analgesic effect in animal models for orofacial pain

Hecogenin acetate (HA) is a steroidal sapogenin-acetylated with pharmacological properties which have already been described in the literature such as, anti-inflammatory, anti-hyperalgesic and antinociceptive, but it has low solubility in aqueous media. Therefore, in an attempt to overcome this, we set out to create inclusion complexes between HA and b-cyclodextrin (b-CD) and evaluate the antinociceptive effects in the orofacial nociception in mice. The complexes were prepared using different methods in the molar ratios 1:1 and 1:2 and characterized physicochemically. The results of the physicochemical characterization elucidated inclusion complexes formation between b-CD and HA by freeze drying method in the molar ratio 1:2, which obtained a complexation efficiency of 92% and produced superior analgesic effect in animal models for orofacial pain at a lower dose when compared to HA alone.

Correlation between DNA/HSA-interactions and antimalarial activity of acridine derivatives: Proposing a possible mechanism of action

Acridines are considered an important class of compounds due to their wide variety of biological activities. In this work, we synthesized four acridine derivatives (1-4) and evaluated their biological activity against the Plasmodium falciparum W2 line, as well as studied the interaction with ctDNA and HSA using spectroscopic techniques and molecular docking. The acridine derivative 2 (IC50 = 0.90 ± 0.08 μM) was more effective against P. falciparum than primaquine (IC50 = 1.70 ± 0.10 μM) and similar to amsacrine (IC50 = 0.80 ± 0.10 μM). In the fluorescence and UV-vis assays, it was verified that the acridine derivatives interact with ctDNA and HSA leading to a non-fluorescent supramolecular complex formation. The non-covalent binding constants ranged from 2.09 to 7.76 × 103 M-1, indicating moderate interaction with ctDNA. Through experiments with KI, fluorescence contact energy transfer and competition assays were possible to characterize the main non-covalent binding mode of the acridines evaluated with ctDNA as intercalation. The binding constants obtained showed a high linear correlation with the IC50 values against the antimalarial activity, suggesting that DNA may be the main biological target of these molecules. Finally, HSA interaction studies were performed and all evaluated compounds bind to the site II of the protein. The less active compounds (1 and 3) presented the highest affinity to HSA, indicating that the interaction with carrier protein can affect the (bio)availability of these compounds to the biological target.

Dynamic Simulation, Docking and DFT Studies Applied to a Set of Anti-Acetylcholinesterase Inhibitors in the enzyme β-Secretase (BACE-1): An Important Therapeutic Target in Alzheimer's Disease

BACKGROUND Alzheimer`s disease (AD) affects mainly elderly people over 60 years of age. Currently, there are more than 35 million people with this disease worldwide. The enzyme β-secretase is involved in the processing of the amyloid precursor protein and plays a key role in the physiopathology of AD. The action of some acetylcholinesterase inhibitors (AChEI) as β-secretase inhibitors has been reported. OBJECTIVE The aim of this study was to highlight the modes of the binding of acetylcholinesterase ligands onto the active site of the β-secretase enzyme. METHODS Molecular dynamics and docking were used in order to identify pivotal interactions that favor the inhibitory activity and provide a rational basis for planning novel β-secretase inhibitors. Additionally, density functional theory (DFT) was used to provide accurate energy values for the complexes. A mechanistic study of the amide hydrolysis was also performed at the M06/6-31G(d) basis set. RESULTS Of the 100 AChE inhibitors, 10 were able to interact with Asp32 and/or Asp228 residues from the enzyme BACE-1, suggesting that these could act as multi-target compounds. These inhibitors were selected for DFT studies in order to provide more accurate energy values. Interestingly, the range of energy values (-27.01 to -8.64 kJ mol-1) obtained was in agreement with the anti-AChE activity. The results obtained in the mechanistic study of compound 93 using DFT are in agreement with theoretical studies described in the literature. CONCLUSION The results reported in this study will advance our understanding of the influence of the distinct chemical structures of inhibitors at the active site and aid the development of new virtual screening protocols to design novel AChE multi-target inhibitors.