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  • 60 Reads
Synthesis and photophysical characterization of 2’-aminochalcones

Chalcones have several biological activities and currently are very studied due to their high therapeutic potential. They can have antitumor, anti-inflammatory, antifungal and antibacterial properties.1 These compounds occur in Nature as secondary metabolites of terrestrial plants and are precursors of flavonoids biosynthesis.2 Generally, they are not luminescent, but derivatives with some particular patterns of substitution can present fair quantum yields.3

Excited State Intramolecular Proton Transfer (ESIPT) is a particular case of tautomerization, and molecules exhibit ESIPT fluorescence if their structures incorporate an intramolecular hydrogen bonding interaction between a hydrogen donor (-OH or -NH) and a hydrogen acceptor.4 The intramolecular hydrogen bonding plays a crucial role in the proton transfer process.5 If the dye is fluorescent, emission from both tautomers may be observed, leading to a dual emission.6

Here, we report the synthesis and photophysical characterizations of 2’-aminochalcones, substituted with electron donating or withdrawing groups, which could be used as markers to study the environment of cellular organelles.

  • Open access
  • 151 Reads
Lead finding from plant Cymbopogon citratus with Immunomodulator Potentials through in silico methods

The aim of this study was to examine correlation between immunomodulators and molecular properties of the Cymbopogon citratus derivatives in search of a lead compound through molinspiration cheminformatics software. Ten naturally occurring and derivatives of Cymbopogon citratus were selected for bioactivity prediction and drug likeness score on the basis of Lipinski’s rule. All of the compounds fulfilled Lipinski’s rule as their Milog P score was below 5 suggesting these compounds are means these shows good permeability across cell membrane. All the screened compounds had minimum and no violations of Lipinski rule. Cymbopogon citratus and its derivatives showed good bioactivity score for drug targets including nuclear receptor ligand, protease inhibitor and enzyme inhibition and thus expected to have excellent pharmacological activity in vivo. The results of this study justify their topical application as immunomodulators action but some structural modifications in order to make the compound more polar will definitely improve oral bioavailability and thus the usefulness and therapeutic efficacy of Cymbopogon citratus . All the Cymbopogon citratus derivatives, are predicted to be orally active and is considered as a potential candidate for the further research as its bioactivity score due to high affinity for various drug targets was better than the standard as well as among other tested compounds.

  • Open access
  • 81 Reads
An in silico approach to enzymatic synthesis of fucooligosaccharides using α-L-fucosidase from Thermotoga maritima

Fucooligosaccharides are the main group into the human milk oligosaccharides. Due to their beneficial properties, a series of synthetic methods have been proposed to obtain them. In this way, the α-L-fucosidase from Thermotoga maritima has emerged as a powerful catalyst for fucooligosaccharides production. Nonetheless, the limited options in substrates for transfucosylation reactions have delayed its wider application. Thus, the present work aimed to compare the reactivity of fucose, pNP-fucose, and ethyl-fucose, as well as the molecular interactions among these fucosyl-donors and the enzyme through a DFT study and docking analysis. DFT analysis was carried out through B3LYP/6-311++G(2d,2p) level of theory, while docking analysis was made for hydrolysis and transfucosylation procedures by Autodock VINA. Both anomers of lactose and fucosyl-donors were full geometry optimized in aqueous phase, and HOMO-LUMO descriptors were calculated. Therefore, band gaps from -7.14571 to -4.24429 eV were found, where α/β-pNP-fucose and α-fucose were the three more reactive compounds. Concerning docking study, coupling energies between -6.4 to -5.5 kcal·mol-1 were shown, being the α-pNP-fucose and α/β-ethyl-fucose the substrates with the lower enzyme affinity. In the case of lactose affinity to the complex β-fucose/enzyme, the disaccharide showed binding affinity energy of -5.7 and -5.8 kcal·mol-1 for the α- and β-anomer, respectively. As a consequence, results suggest that the best fucosyl-donors for hydrolysis are those who maintain lower affinity with the enzyme active site, while there is not a significant difference among lactose anomers for their bonding to the enzyme-substrate complex.

  • Open access
  • 79 Reads
New BODIPY Dye with a Large Stokes Shift for Biopolymer Labelling

As the most abundant protein with a variety of physiological functions, human serum albumin (HSA) has been used extensively for the delivery of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare albumin-based multimodal imaging probes and agents for Boron Neutron Capture Therapy (BNCT). For this purpose, boron containing BODIPY dye was designed and synthesized. BODIPY dyes are photostable neutral derivatives of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene. These are widely used as chemosensors, laser materials and molecular probes. In the same time, BODIPY dyes as most other fluorophores have small or moderate Stokes shifts. Large Stokes shifts are preferred for fluorophores because of higher sensitivity of such probes and sensors. We succeeded to perform an annelation of pyrrole ring with cumarine heterocyclic system and achieved a remarkable difference in absorption and emission maximum of obtained fluorophore up to 100 nm. Moreover, this BODIPY dye was equipped with linker arm and was functionalized with a maleimide residue specifically reactive towards thiol groups of proteins. The released sulfhydryl groups of the homocysteine functional handle in thiolactone modified HSA was labeled with BODIPY dye to prepare a labeled albumin-BODIPY dye conjugate confirmed by MALDI-TOF-MS, UV-VIS and fluorescent emission spectra. This is the basis for a novel BODIPY dye -albumin theranostic for BNCT. These results provide further impetus to develop derivatives of HSA for delivery of Boron to cancer cells.

  • Open access
  • 75 Reads
Synthesis of porphyrins with ABAB symmetry from dipyrromethanes as potential phototherapeutic agents

Porphyrin derivatives have been used as photosensitizers in the photodynamic inactivation of microorganisms. However, depending on the substituents on the periphery of the tetrapyrrolic macrocycle, these molecules tend to aggregate, producing a loss of photodynamic activity. Thus, to achieve effective photoinactivation, these compounds can bind to different supports forming photoactive materials. In this sense, it is interesting to develop porphyrins asymmetrically substituted in the meso positions by two different structures (A and B). In these compounds, structure A has a functional group that allows covalent attachment to other molecules, while B is substituted by groups that allows changing the properties of the tetrapyrrolic macrocycle.

In this work, asymmetrically meso-substituted porphyrins were synthesized with ABAB symmetry patterns. The approach required the formation of dipyrromethanes, which were obtained from the condensation of an aldehyde (pentafluorobenzaldehyde or N,N-diphenylaminobenzaldehyde) with a large excess of pyrrole (1:47 aldehyde/pyrrole mol ratio), catalyzed by trifluoroacetic acid in 70-94% yields. Then, acid catalyzed condensation of these dipyrromethanes with an aldehyde (N,N-dimethylaminobenzaldehyde, N-ethyl-3-carbazolecarbaldehyde or 4-carboxymethylbenzaldehyde) (1:1 mol ratio) in dichloromethane, followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone affords the diseased porphyrins in 25-40% yields. These ABAB-porphyrins are interesting starting materials to obtain photoactive molecular structures as potential phototherapeutic agents.

  • Open access
  • 201 Reads
Chemical Synthesis and Hemi-synthesis of novel benzimidazoles derivatives using microwave-assisted process: chemical characterization, bioactivities, and molecular docking study

Benzimidazoles derivatives represent a class of heterocyclic compounds that exhibit a wide range of pharmaceutical properties. The present study aimed to investigate the in-vitro antioxidant and antimicrobial activities of newly synthesized benzimidazoles derivatives. Compound 1b, (2-(1H-1,3-benzodiazol-2-yl) phenol) was synthesized by reacting o-phenylenediamine (OPA) with chemical salicylaldehyde, while compound 2b, (2-(1E)-2-phenylethenyl-1H-1,3-benzodiazole) and 3b (2-(1E)-2,6-dimethylhepta-1,5-dien-1-yl-1H-1,3-benzodiazole) were obtained through hemi-synthesis process of respectively the cinnamon (cinnamaldehyde, 85%), and lemongrass (citral, 49,5%) essential oils previously characterized by GCMS. Compounds 4b, 2-phenyl-1H-benzimidazole, 5b, (2-(1H-benzimidazol-2-yl)phenol), and 6b, (5-(1H-benzimidazol-2-yl)benzene-1,2,3-triol) were synthesized with click chemistry method by reacting the OPA with Benzoic acid, salicylic acid, and gallic acid directly in ethanol under microwave irradiation. The structure/purity of the synthesized compounds was clarified by spectroscopy ATR-FTIR and NMR 1H. Compounds 1b-6b were screened for their antioxidant activity by using four complementary in vitro assays: DPPH scavenging activity, ferric ion reducing power, β-carotene bleaching inhibition, and TBARS formation inhibition. All the tested compounds showed antioxidant potential with different performances. Antimicrobial activity was investigated against ATCC strains (three Gram- bacteria: Escherichia coli, Salmonella typhi, and Pseudomonas aeruginosa, one Gram+ bacteria: Staphylococcus aureus, and one yeast stain Candida albicans) through the determination of MIC and MBC by using the microdilution method and rapid colorimetric test of p-iodonitrotetrazolium chloride (INT). Compound 6b exhibited the highest potential especially against S. aureus (CMI = 0,156 mg.mL-1) followed S. typhi and C. albicans (CMI = 0.3125 mg.mL-1), then E.coli and and P. aeruginosa by compound 1b also showed a great potential against S. aureus et C. albicans (CMI ˂0.3125 mg/mL), followed by E.coli and S. typhi (CMI = 0.3125mg/mL), and P. aeruginosa (CMI = 0.625 mg/mL). A further molecular docking was proceeded using Autodock vina software on s. aureus thymidylate kinase TMK-protein to highlight the structure-activity relationship of the potent molecules.

  • Open access
  • 69 Reads
Evaluation of Organophosphate Pesticide Residues in Food using the Partial Least Squares Method

Organophosphourus (OP) chemicals were broadly used as insecticides and in the treatment of human diseases such as the malaria mosquitoes, parasitosis, myasthenia, and glaucoma. The OP toxicity is well known, they can cause environmental and health problems and the possibility to accumulate in the food chain. The acceptable daily intake (ADI) can be considered as a measure of the effect of pesticide residues in food on human health. In this paper the partial least squares (PLS) approach is used to evaluate the ADIs (expressed as pADIs) of a series of 46 structurally diverse OPs. OP structures were pre-optimized using the MMFF94s force field and structural descriptors were calculated for the minimum energy conformers. This dataset was divided into 26 training compounds, and 20 pesticides were included in the prediction set. Several criteria to check the model robustness, overfitting and the potential outliers in the X and Y space were employed. The PLS results indicate that new experimental toxicological data would be needed for five out of the 46 OPs, to improve their known ADI values, for qualitative and quantitative dietary long-term risk assessments.

  • Open access
  • 94 Reads
Insight into the influence of the chiral molecular symmetry on the chiroptics of fluorescent BINOL-based boron chelates

Among all the technological applications based on photonics, those based on chiroptical phenomena (particularly, circularly polarized luminescence, CPL) have special relevance, mainly owing to the higher resolution of the circularly polarized over the linearly polarized or the unpolarized light. However, the design of emitters efficiently enabling CPL is not an easy task because it is necessary to combine, in the same structure, a high fluorescence quantum yield and a high level of circular polarization in the emission. Among all the possible chemical systems that show circularly polarized luminescence, the CPL-SOMs (simple organic molecules enabling CPL) have gained exponential interest in the last years. The reason for the growing interest in these emitters lies in their potential for the development of specific CPL materials due to properties associated with their organic nature (low molecular weight, organic-solvent solubility) and their high capacity of absorbing and emitting light, which, in addition, can be adjusted by workable chemical modifications of the chromophore. However, although organic chromophores usually show bright fluorescence, their levels of circular polarization are still very small in all cases. In this regard, there is a need for systematic studies directed towards a deeper knowledge on the structural factors ruling the chiroptical behavior of CPL-SOMs. In this communication, we study and discuss the influence of the chiral symmetry point group (C1, C2 and D3) on the chiroptical behavior of simple fluorescent boron chelates (BODIPY and related BOPHY analogs) to shed light on the chiroptical behavior of BODIPY-based and BODIPY-like CPL-SOMs.

  • Open access
  • 81 Reads
Theoretical Elucidation of the Formation of γ-butyrolactone from Haloacetate

γ-butyrolactone is a chemical intermediate used in many organic reactions. It is also used in phytochemistry and biology for the production of growth hormones. Experimentally; the obtaining of γ-butyrolactone is done by several chemical routes; the addition of haloacetates to alkenes is an example.

In this study; we will be interested on the theoretical elucidation of the addition reaction of Bromoacetate; Chloroacetate and Iodoacetate on an unsubstituted alkene to form γ-butyrolactone. The transition state theory approach was used; in the first time; and the different stationary states were optimized at the DFT (B3LYP) level with the basis 6-31G (d, p). The transition states have been well located; optimized and successfully confirmed.

The different reactivity indices resulting from the conceptual DFT were calculated; in the second time; in order to identify the different reactional sites. A good agreement was found between the different theoretical approaches used in this study.

  • Open access
  • 60 Reads
Crown Ether Benzoxazolyl-alanines as Fluorimetric Chemosensors for the Detection of Palladium in Aqueous Environment

Palladium (Pd) is a widely applied transition metal, for example in dental restorations, chemical catalysts, jewellery, electronic equipment, automobile industry, among others. As a consequence of its wide application, high levels of palladium in the environment have been reported, representing a risk to human health. So far, a variety of small fluorescence probes have been successfully developed for palladium detection, but there is an interest to design improved water-soluble probes for recognition of this metal in biological and environmental systems.

Considering the research group´s experience on fluorescent chemosensors based on unnatural amino acid derivatives containing heterocyclic fluorescent and/or coordination units at the side chain, we report herein the evaluation of two benzoxazolyl-alanine derivatives bearing a crown ether moiety as potential fluorimetric chemosensors for palladium detection in aqueous media. Preliminary chemosensory studies for these unnatural amino acids in the presence of selected metal cations, with biological and environmental relevance, were performed in acetonitrile solution and in aqueous mixtures of sodium dodecyl sulfate (SDS, 20 mM, pH 7.5) solution with acetonitrile, 90:10 v/v. As expected, these probes had a fluorescence response for different cations in acetonitrile solutions but, most importantly, in aqueous solutions both crown ether benzoxazolyl-alanine derivatives displayed a selective fluorescence response in the presence of palladium.