Publications

Abstract In recent years, the use of boron-containing reagents in palladium-assisted C-C coupling reactions (the Suzuki reaction) has gained prominence due to the vast array of reagents commercially available. Consequently, the generation of carbon carbon bonds, namely of functionalized biphenyl systems, is at present considered the backbone of organic synthesis. In this context, the design of eco-friendly protocols for the Suzuki reaction employing water as a solvent and the use of microwave-assisted procedures are imperative from an industrial point of view. The series of laboratory experiences described highlight the skillfulness of microwave-assisted synthesis to promote environmentally friendly Suzuki reactions. In the first laboratory class, 1(4-hydroxy-4'-methoxy-[1,1'-biphenyl]-3-yl)ethanone and 1-(4'-chloro-4-hydroxy-[1,1'-biphenyl]-3-yl)ethanone are synthesized, and the crude products are obtained and purified. Students become acquainted with microwave equipment and several laboratory techniques, such as extraction, purification by filtration with celite, column chromatography, and thin-layer chromatography. In the second laboratory class, students check the purity of the compounds and acquire H-1 and C-13 NMR spectral data. The synthesized phenylacetophenone derivatives are key intermediates for the synthesis of many biological active molecules, namely, flavonoids, chromones, or coumarins, which are privileged structures for drug discovery. The experiments can be also performed with diverse arylboronic acids containing different electron donating and withdrawing groups, allowing the synthesis of a small library of benzopyran precursors. The experiments have been tested for three years by 75 graduate students in applied organic chemistry or medicinal chemistry curriculum units.

Abstract In this study, a theoretical approach was used to study the UV absorption of the UVB filter, 4- methylbenzylidene camphor. The main objective of this work was to design new UVA filters based on this rather photo- stable compound, so that photo- degradation in this UV region can be avoided without the use of other molecules. This objective was achieved by the simultaneous addition of two appropriate substituents, which led to red- shifts of up to 0.69 eV while maintaining appreciable oscillator strength. Also, useful structure- energy relationships were derived, which allow for the development of more UVA filters based on 4- methylbenzylidene camphor.

Abstract Hydroxycinnamic derivatives based on ferulic and caffeic acids were designed to meet the pharmacokinetic requirements to cross the blood-brain barrier and to display neuroprotective activity within the central nervous system. Biological screening included the assessment of acetylcholinesterase and glycogen synthase kinase 3b inhibition, iron chelation properties, in vitro blood-brain barrier permeability, evaluation of cytotoxicity and neuroprotection against 6-hydroxydopamine induced damage in SH-SY5Y cells. Although the chemical modifications did not significantly alter the in vitro activity of the parent compounds, the results of the PAMPA-BBB assay show that some derivatives have higher diffusion rates and may reach the brain. The majority of the synthesized compounds did not display cytotoxicity and successfully prevent 6-hydroxydopamine damage. In this series, compound 14 stands out as a promising neuroprotective agent combining a number of key features: iron chelation, neuroprotection against oxidative damage, mild acetylcholinesterase activity and ability to permeate the blood-brain barrier. This biology-oriented approach provides new tools for the generation of new chemical entities to tackle the oxidative damage associated with neurodegenerative disorders.

Abstract New lipophilic hydroxycinnamic acid based derivatives were designed and synthesized and their antioxidant and neuroprotective activities evaluated. The chemical modification introduced in the cinnamic acid scaffold leads to compounds with amplified lipophilicity and in general with increased antioxidant activity when compared to natural models (caffeic and ferulic acids). The compounds did not display cytotoxicity and present a significant neuroprotective effect against 6-OH-DA induced damage to SH-SY5Y cells. Compound 6 stands out as an efficient radical scavenger and iron(II) chelator that ensures drug-like properties. Moreover, neuroprotection against oxidative damage was observed even at low concentration (1 mu M). Therefore, compound 6 developed by a biology-oriented approach displays a combination of important features for a further optimization process that will generate a new effective antioxidant with therapeutic application for oxidative-stress-related events, namely neurodegenerative diseases.

Abstract The increased bacterial multidrug resistance caused by inappropriate use and overuse of antimicrobials is a global concern. To circumvent this issue, a quest for the development of new active agents has been widely recognized. Some phytochemical products, produced by plants as part of their chemical defense strategies, are regarded as new stimulii to develop novel antimicrobials that are not as vulnerable as current drugs to bacterial resistance mechanisms. In this study, the antimicrobial activity and mode of action of caffeic acid (CAF) and a series of CAF alkyl esters was assessed against Escherichia coli and Staphylococcus aureus, with the aim of analyzing the influence of the alkyl ester side chain length on the activity. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), changes in physicochemical surface properties and intracellular potassium leakage were used as physiological indices for the antimicrobial mode of action. CAF alkyl esters were found to be effective antimicrobial agents against both bacteria. Their activity was directly dependent on their lipophilicity, which affected bacterial susceptibility, the physicochemical properties of the bacteria and the integrity of the membranes. E. coli was less susceptible than S. aureus to the action of the compounds. Longer alkyl side chains were more effective against the Gram-positive bacterium, while medium length alkyl side chain compounds were more effective against the Gram-negative bacterium. Caffeic acid derivatives are proposed to act as cell permeabilizers, inducing membrane alterations, causing rupture with potassium leakage, particularly on the Gram positive bacterium, and consequent cell death.

Abstract 4-tert-Butyl-4 '-methoxydibenzoylmethane (BMDM) is a widely used ultraviolet A filter. In this work, we have studied the effect of chlorine and dissolved organic matter (DOM) concentrations on the stability of UV filter (BMDM) present in two commercial sunscreen cream formulations in water. An experimental design was used to assess the effect of the two experimental factors on the degradation of BMDM. Higher concentrations of chlorine lead to higher degradation percentages of BMDM and higher concentrations of DOM inhibit its degradation. Moreover, a mono and a dichloro derivate of BMDM were identified as by-products.

Abstract Gene delivery targeting mitochondria has the potential to transform the therapeutic landscape of mitochondrial genetic diseases. Taking advantage of the nonuniversal genetic code used by mitochondria, a plasmid DNA construct able to be specifically expressed in these organelles was designed by including a codon, which codes for an amino acid only if read by the mitochondrial ribosomes. In the present work, gemini surfactants were shown to successfully deliver plasmid DNA to mitochondria. Gemini surfactant-based DNA complexes were taken up by cells through a variety of routes, including endocytic pathways, and showed propensity for inducing membrane destabilization under acidic conditions, thus facilitating cytoplasmic release of DNA. Furthermore, the complexes interacted extensively with lipid membrane models mimicking the composition of the mitochondrial membrane, which predicts a favored interaction of the complexes with mitochondria in the intracellular environment. This work unravels new possibilities for gene therapy toward mitochondrial diseases.

Abstract A firefly luciferase (LUC)-based bioluminescent assay for total free fatty acids (FFA) is presented. It is based on LUC's capability of converting FFA into fatty acyl-adenylates with consumption of adenosine 5-triphosphate (ATP). Since ATP is a cosubstrate in LUC's bioluminescent reaction, together with firefly d-luciferin (d-LH2) and atmospheric oxygen (O-2), any reduction in the assay's ATP content will lead to a decrease in the bioluminescent signal, which is proportional to the amount of FFA. Using FFA mixtures containing myristic (14:0), palmitic (16:0), stearic (18:0), oleic (18:1) and arachidonic acid (20:4) in ethanol, the assay was optimized through statistical experimental design methodology, namely fractional factorial (screening) and central composite (optimization) designs. The optimized method requires 2L of sample per tube in a final reaction volume of 50L. It is linear in the concentration range from 1 to 20m, with limits of detection (LOD) and quantitation (LOQ) of 1.3 and 4.5m, respectively. The method proved to be simple to perform, demands low reagent volumes, it is sensitive and robust and may be adapted to high-throughput screening.

Abstract Gemini surfactants have been extensively used for in vitro gene delivery. Amino acid-derived gemini surfactants combine the special aggregation properties characteristic of the gemini surfactants with high biocompatibility and biodegradability. In this work, novel serine-derived gemini surfactants, differing in alkyl chain lengths and in the linker group bridging the spacer to the headgroups (amine, amide and ester), were evaluated for their ability to mediate gene delivery either per se or in combination with helper lipids. Gemini surfactant-based DNA complexes were characterized in terms of hydrodynamic diameter, surface charge, stability in aqueous buffer and ability to protect DNA. Efficient formulations, able to transfect up to 50% of the cells without causing toxicity, were found at very low surfactant/DNA charge ratios (1/1-2/1). The most efficient complexes presented sizes suitable for intravenous administration and negative surface charge, a feature known to preclude potentially adverse interactions with serum components. This work brings forward a new family of gemini surfactants with great potential as gene delivery systems.

Abstract Species with three-membered rings and the amide linkage are well studied. A quick perusal of the literature with SciFinder finds some 50 000 references to cyclopropanes and almost 300 000 references to amides. In the current paper, we discuss the structure and energetics of two understudied three-membered ring amides, 1,2-oxaziridine-3-one (5) (simultaneously describable as the simplest cyclic carbamate and simplest hydroxamate) and aziridine-2,3-dione (7) (simultaneously describable as the simplest imide and simplest alpha-ketoamide), with but 5 and nearly 10 references, respectively, for these two classes of compounds. Neither 1,2-oxaziridine-3-one (5) nor aziridine-2,3-dione (7), nor any derivative thereof, has been isolated. Calculational theory ameliorates the paucity of experimental information. The current study reports our computational findings for these and related species (e.g., enols and imidols) where we have used the G3(MP2)//B3LYP method.