Please login first

List of accepted submissions

Show results per page
Find papers
  • Open access
  • 64 Reads
Synthesis and preliminary antibacterial evaluation of a 2,4,5-tri(hetero)arylimidazole derivative.

The imidazole ring is a planar heterocycle whose derivatives are applied in several scientific areas, such as Medicinal, Materials and Supramolecular Chemistry. The presence of the imidazole ring in these structures is the key to the development of new drugs, since this heterocycle is present in several naturally occurring biological structures. Therefore, over the past few decades, several imidazole derivatives have been synthesized and occupy a unique position in the field of Medicinal Chemistry due to their diverse biological activities. In order to continue the work developed by the research group, we report the synthesis of 2,4,5-tri(hetero)arylimidazole derivatives and their respective characterization by 1H and 13C nuclear magnetic resonance (NMR) and UV-Vis. spectroscopies. As a complement of the characterisation of the synthesised 2,4,5-tri(hetero)arylimidazole derivatives, a screening for antibacterial activity showed inhibition of Staphylococcus aureus proliferation, suggesting antibacterial activity. Therefore these new compounds have the potential for the development of new drugs.

  • Open access
  • 61 Reads
Nanosystems for encapsulation and release of plant extracts with insecticidal activity

Besides the pharmaceutical potential of several plant extracts, their use as repellents and green insecticides has been recently described, but this application can be hampered by the volatility and easy degradation of the active compounds.

The encapsulation in suitable nanostructures is a relevant strategy for preservation and controlled release of bioactive compounds, allowing a safe application. In this work and following previous studies, the extracts of Mentha suaveolens Ehrh. and Phytolacca americana L. in dichloromethane, after removal of chlorophylls, demonstrated potential as biopesticides in assays using the Sf9 (Spodoptera frugiperda) insect cell line.

Encapsulation in chitosan nanostructures and liposomes of soybean lecithin were carried out, the latter prepared either by thin film hydration or ethanolic injection methods. For chitosan, the ionic gelation technique was used. The nanosystems were characterized regarding their size and polydispersity. Encapsulation efficiencies of the extracts were determined (being higher than 60%) and the release profiles were fitted with suitable models. Liposomes generally allowed a delayed release of the extracts, while chitosan nanosystems are suitable for a faster and complete release of the potential bioinsecticides.

  • Open access
  • 77 Reads
In Silico Identification of Protein Targets Associated to the Insecticide Activity of Eugenol Derivatives

The control of insect pests and the need for increased food production due to the world population growth, together with the environmental issues associated to synthetic pesticides, has stimulated the development of new and “greener” alternatives, based on natural compounds. Eugenol is a natural compound that is the major component of clove oil. It has demonstrated antimicrobial and antioxidant activity, being also a powerful insecticide. Recently, new eugenol derivatives have been developed, with some molecules displaying increased insecticide activity. One of the difficulties associated to the rational development of new eugenol derivatives with enhanced insecticidal activity lies in the lack of knowledge of the specific protein target responsible for its activity and to the binding conformation of these molecules.

Here, we report the application of an integrated molecular modelling - inverted virtual screening protocol of a collection of eugenol derivatives with confirmed insecticide activity against a molecular library of protein targets typically associated with the insecticide activity of natural compounds. The protocol included 6 different scoring functions from popular docking software alternatives. The results consistently show a marked preference for interaction of the eugenol derivatives with the odorant binding proteins (OBPs) in insect species. Interestingly, OBPs have been regarded as promising targets in the insect periphery nerve system for environmentally-friendly approaches in insect pest management. The present results provide clues for the rational development of new eugenol derivatives as bioinsecticides targeting OBPs.

  • Open access
  • 75 Reads
Carvacrol derivatives with potential insecticidal activity

Synthetic pesticides have been used for decades to manage pest control in crops, in order to avoid considerable damage and production losses due to pathogens, insects and other pest species. Nowadays, because of environmental and health issues, synthetic pesticides are being gradually replaced by botanical pesticides. Essential oils (EOs), plant’s secondary metabolites of low molecular weight and strong organoleptic properties, have been investigated as resources of potentially useful bioactive compounds, and it is known that they have an important role in the interactions between insects and plants. Carvacrol, a phenolic compound that is the main component in oregano essential oil, displays antimicrobial, antifungal, and insecticidal activities.

Considering these facts, the present investigation is focused on synthesis of new carvacrol derivatives possessing aliphatic carbon chains with different sizes as hydroxyl group substituents. All compounds were fully characterized by the usual analytical techniques, and their insecticide activity against the insect cell line Sf9 (Spodoptera frugiperda) was evaluated, to assess the potential application of these new derivatives as biopesticides.

  • Open access
  • 74 Reads
Synthesis and insecticidal activity of O-alkylated oxirane eugenol derivatives

In the last decades, the need to prevent diseases and damage caused by the attack of various pests on plants, has led to the application of high amounts of synthetic pesticides, including insecticides, which has resulted in the development of resistance to them by several harmful organisms. As an alternative, natural products with insecticide activity have been shown promise for insect control in agriculture. Essential oils (EOs) exhibit antimicrobial activities with particular potential as insecticides. Structural modifications in the constituents of EOs can further enhance their biocidal effect.

Eugenol, the major component of clove oil, presents numerous applications including in pharmaceutical, food and agricultural industries. It is an important insecticide with large efficiency on a wide variety of domestic arthropod pests.

In the present work, O-alkylated eugenol derivatives, bearing a propyl chain with hydroxyl, methyl and ethyl esters as terminals were synthesised and further converted into the corresponding oxiranes. Oxirane derivatives were then evaluated against their effect upon the viability of the insect cell line Sf9 (Spodoptera frugiperda), in comparison with the starting O-alkylates. The results pointing to their potential as bioinsecticides, with structural changes eliciting marked effects in terms of potency.

  • Open access
  • 63 Reads
Encapsulation in lipid nanosystems of eugenol oxirane insecticide

Essential oils (EOs) have been studied owing to their properties, such as remarkable biological activities and health promoting benefits, including analgesic, anti-inflammatory, antibiotic, antioxidant and antimicrobial activities, as well as potential insecticides.

In spite of all their properties, EOs present low water solubility, poor bioavailability, volatility, reduced stability, and low resistance to environmental stresses like light, oxygen, and temperature which difficult their applications.

To mitigate these limitations, EOs can be incorporated into nanoencapsulation systems, this being a promising approach for the controlled release and preservation of their properties.

Considering these facts, in the present work, an eugenol oxirane, namely ethyl 4-(2-methoxy-4-(oxiran-2-ylmethyl)phenoxy)butanoate, with promising insecticidal activity, was submitted to encapsulation assays in lipid nanosystems, in order to boost its application as bioinsecticide.

  • Open access
  • 42 Reads
Synthesis of amino alcohols from eugenol and their insecticidal activity against Sf9 cell line

Structural changes of natural biologically active compounds are an important strategy to improve biological activity and at the same time to reduce possible side effects.

Eugenol is a major constituent of clove essential oil with interesting biological activity, namely antimicrobial and antioxidant. Also the ß-amino alcohol moiety represents an important core in pharmaceutical industry; drugs, such as salbutamol and propranolol, are amongst the most important therapeutical agents on the market with this feature.

In the present work, a series of amino alcohols were prepared from eugenol epoxide; the epoxide was prepared from eugenol using m-CPBA, and was reacted with a series of amines affording the corresponding ß-amino alcohols in good yields. The compounds obtained were purified and fully characterised by usual analytical techniques, namely NMR spectroscopy and mass spectrometry.

Previous work carried out in our lab has shown interesting biological activity of some eugenol derivatives. The potential of these new compounds will be evaluated as biopesticides in assays using the Sf9 (Spodoptera frugiperda) insect cell line, and the results will be presented in this communication.

  • Open access
  • 70 Reads
Effect on Cycloaddition Reactions of Aqueous Micellar Systems formed by Amphiphilic Imidazolium Ionic Liquids

The micellar effect on a Diels-Alder reaction (DA) was analyzed taking advantage of the property presented by Ionic Liquids (ILs) based on 1-alkyl-3-methylimidazolium cations by having amphiphilic character when the alkyl group is a long hydrocarbon chain -12 carbon atoms [C12mim]-. These ILs can act as surfactants forming micelles in aqueous solution.

The reactive system studied consists of nitrofuran and isoprene which allows obtaining benzofuran through green synthetic strategie.

These “new microheterogeneous systems” would allow a better solubilization of non-polar substrates and to adopt reaction conditions softer than the traditional thermal.

  • Open access
  • 60 Reads
One-step mechanism of hydrogen transfer in "amine – triplet nitro compound" system

Nitro compounds in the triplet state are strong oxidizing agents, one of the reactions of which is the excited-state hydrogen atom transfer. The energy characteristics of the reaction of triplet nitromethane with methylamine are obtained using ab-initio methods. MP2 and CASSCF methods were used. Calculated atomic charges has shown that the transfer of a proton must be accompanied by a simultaneous transfer of an electron. Optimization of the reaction complexes showed that in the course of the reaction there is a change in the reaction coordinate. The first stage is a rotation of methylamine molecule and the second stage is a lengthening of the C-H bond. Energetic and geometric parameters calculated by the MP2 and CASSCF methods are very close to each other which means the possibility of using the MP2 method for modeling similar processes as the main one.

  • Open access
  • 106 Reads
Fluorescent Calixarene Dimers: Synthesis and Optical Properties

Supramolecular chemistry has stimulated the attention of the scientific community over the last few decades. Inspired by nature and exploiting the scope of non-covalent interactions such as hydrogen bonding, electrostatics, and π−π stacking, scientists have developed various synthetic systems with potential for application in different fields (e.g. smart materials, catalysts, optical sensors, complexing agents and nanomedicine).

Several calixarene architectures, a benchmark in supramolecular chemistry, were reported by us as highly sensitive and selective chemosensors. In this communication, the synthesis and structural characterization of a new host calixarene dimer having an enlarged intramolecular cavity specially designed to accommodate large molecular species -such as fullerenes - will be present. Sonogashira cross-coupling was used to assemble the entire unit, which holds a fluorogenic carbazole sub-unit.

The new compound was characterized by FT-IR and 1H/13C and 2D NMR techniques and its photophysical properties studied by UV-Vis and fluorescence spectroscopies. A significant photoluminescence and a great stability toward photobleaching were witnessed for dimer.

Studies concerning the capability of new compound to selectively include C60/C70 compounds and metallophthalocyanines are currently ongoing.