Publications

Abstract Coelenterazine is a common substrate used by marine species in enzyme-catalyzed bioluminescent reactions, in which thermal energy is converted into excitation energy. Coelenterazine is also known to emit chemiluminescence, in the absence of enzymes. Moreover, the scaffold of this molecule is present in organisms of eight phyla, making it a prototypical system for marine chemi-/bioluminescence. The characterization of the chemiexcitation step responsible for light emission is essential for future applications in bioimaging, bioanalysis and biomedicine. We have found evidence to support the identification of a neutral dioxetanone intermediate as the responsible for efficient chemiexcitation. This is explained by attractive electrostatic interactions between the CO2 and Coelenteramide moieties, which allow the reacting dioxetanone to spend time in a PES region of degeneracy between singlet ground and excited states. Contrary to expected, there is no relationship between electron (ET)/charge (CT) transfer, from an electron-rich moiety to the peroxide, and efficient chemiexcitation. Thus, neither Chemically Induced Electron-Exchange Luminescence (CIEEL) nor Charge Transfer-Initiated Luminescence (CTIL) can be used to explain imidazopyrazinone-based chemi-/bioluminescence. We have also found a concentration-dependent quenching effect, more prevalent at acidic pH.

Abstract Coelenterazine is a common substrate used by marine species in enzyme-catalyzed bioluminescent reactions, in which thermal energy is converted into light-emission. Besides bioluminescence, Coelenterazine is also known to emit chemiluminescence in aprotic solvents. We report here the study of Coelenterazine chemiluminescence in aqueous solution. Water inhibits light-emission even in mixtures with water content as low as 20%. Moreover, we provide convincing spectroscopic evidence that the presence of water affects the ground state (S-0) chemical reaction, and not the excited state processes (as chemiexcitation and the fluorescent quantum yield). However, the energetics of the S-0 chemical reaction is not affect by addition of water, which points to the inhibition being caused by the reduced lifetime of superoxide anion in water, which is an intermediate in the luminescent reactions of Coelenterazine. This finding indicates that one of the catalytic roles of bioluminescent enzymes is to extend the lifetime of this radical.

Abstract The energetic study of 2-phenylbenzoxazole (PBO), 2-phenylbenzothiazole (PBT), 2-(2-hydroxyphenyl) benzoxazole (HBO) and 2-(2-hydroxyphenyl) benzothiazole (HBT) has been developed either using experimental techniques or computational calculations. The enthalpies of combustion and of sublimation of these compounds were determined and the gas-phase standard molar enthalpies of formation were derived. The experimental techniques used were static or rotating bomb combustion calorimetry, high temperature Calvet microcalorimetry and/or the Knudsen-effusion method. Additionally, we have obtained the gas-phase standard molar enthalpies of formation of these compounds, as well of 2-(2-hydroxyphenyl) benzimidazole (HBI), through high level ab initio calculations, at the G3(MP2)//B3LYP level. The computational study of the molecular structures of all these compounds has been carried out and four possible conformers were observed for the molecules of each compound, where the keto tautomers have always higher energy than the enol forms. Furthermore, the energetic effects associated to the presence of the hydroxyl group on the core of the 2-phenylbenzazole rings, in particular the hydrogen bond network, were also evaluated. (C) 2017 Elsevier Ltd.

Abstract Adenosine receptor (AR) subtypes are involved in several physiological and pharmacological processes. Ligands that are able to selectively modulate one receptor subtype can delay or slow down the progression of diverse diseases. In this context, our research group focused its investigation into the discovery and development of novel, potent and selective AR ligands based on coumarin scaffold. Therefore, a series of 3-phenylcarboxamidocoumarins were synthesized and their affinity for the human AR subtypes was screened by radioligand binding assays for A(1), A(2A) and A(3) receptors and for A(2B) by adenylyl cyclase assay. Compound 26 was found to be the most remarkable, with a hA(1)/hA(3) and hA(2A)/hA(3) selectivity of 42, for the A(3) AR (K-i=2.4m). Receptor-driven molecular modelling studies have provided valuable information on the binding/selectivity data of compound 26 and for the following optimization process. Moreover, compound 26 presents drug-like properties according to the general guidelines linked to the concept.

Abstract The immune system is composed of organs, cells, and soluble factors, which together act to defend the organism against foreign invaders, and is divided into innate and adaptive immune system (or acquired). Antigens are substances (usually foreign macromolecules) recognized by adaptive immune system receptors as dangerous non-self and that immediately initiate a response. While, response against normal body components (itself reaction) may occur as a result of failure in self-tolerance mechanisms, producing different autoimmune diseases which are, in general, progressive, chronic, and self-perpetuating. The available treatments aim to ameliorate or treat symptoms but have serious side-effects due to the high doses needed, as used drugs have in general low water solubility and long treatment periods. Recent advances with resource of nanotechnology aiming to achieve better results in terms of drug bioavailability and targeting to the treatment site of action as well as reduction of side effects will be discussed. In this chapter, five autoimmune diseases were selected, due to their incidence to the general population: the organ-specific diseases diabetes mellitus type I, psoriasis, multiple sclerosis, lupus erythematosus, and rheumatoid arthritis that affect several organs.

Abstract Caffeic acid phenethyl ester (CAPE) is a bioactive polyphenolic compound obtained from propolis extract. Although it has a broad therapeutic potential, the bioavailability of CAPE is limited, due to reduced solubility and poor plasmatic stability. Efforts to reduce these pharmacokinetic drawbacks resulted in the synthesis of caffeic acid phenethyl amide (CAPA). Cyclodextrins have been proved as promising excipients for the formulation of active ingredients. Herein, we report the inclusion complexation behavior and binding ability of CAPE and CAPA with hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The supramolecular interactions were examined through UV and FTIR spectroscopy, DSC, H-1 NMR and 2D ROESY. The CAPE/HP-beta-CD and CAPA/HP-beta-CD inclusion complexes stability constants were determined to be, respectively, 2911.6 and 584.6 M-1 in water and 2866.2 and 700.1 M-1 at physiological pH. The aqueous solubility increased notably, proving that HP-beta-CD can be potentially useful to improve the biological, chemical and physical properties of CAPE and CAPA.

Abstract Gastric cancer is the third leading cause of cancer-related mortality worldwide and despite advances in prevention, diagnosis and therapy, it is still regarded as a global health concern. The efficacy of the therapies for gastric cancer is limited by a poor response to currently available therapeutic regimens. One of the reasons that may explain these poor clinical outcomes is the highly heterogeneous nature of this disease. In this sense, it is essential to discover new molecular agents capable of targeting various gastric cancer subtypes simultaneously. Here, we present a multi-objective approach for the ligand-based virtual screening discovery of chemical compounds simultaneously active against the gastric cancer cell lines AGS, NCI-N87 and SNU-1. The proposed approach relays in a novel methodology based on the development of ensemble models for the bioactivity prediction against each individual gastric cancer cell line. The methodology includes the aggregation of one ensemble per cell line using a desirability-based algorithm into virtual screening protocols. Our research leads to the proposal of a multi-targeted virtual screening protocol able to achieve high enrichment of known chemicals with anti-gastric cancer activity. Specifically, our results indicate that, using the proposed protocol, it is possible to retrieve almost 20 more times multi-targeted compounds in the first 1% of the ranked list than what is expected from a uniform distribution of the active ones in the virtual screening database. More importantly, the proposed protocol attains an outstanding initial enrichment of known multi-targeted anti-gastric cancer agents.