Juan A. Páez

Tacrine–Melatonin Hybrids as Multifunctional Agents for Alzheimer's Disease, with Cholinergic, Antioxidant, and Neuroprotective Properties

Tacrine–melatonin hybrids are potential multifunctional drugs for Alzheimers disease that may simultaneously palliate intellectual deficits and protect the brain against both β‐amyloid peptide and oxidative stress. Molecular modeling studies show that they target both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. They are nontoxic and may be able to penetrate the CNS, according to in vitro PAMPA‐BBB assays.

Elucidation of the Molecular Recognition of Bacterial Cell Wall by Modular Pneumococcal Phage Endolysin CPL-1 *□

Pneumococcal bacteriophage-encoded lysins are modular proteins that have been shown to act as enzymatic antimicrobial agents (enzybiotics) in treatment of streptococcal infections. The first x-ray crystal structures of the Cpl-1 lysin, encoded by the pneumococcal phage Cp-1, in complex with three bacterial cell wall peptidoglycan (PG) analogues are reported herein. The Cpl-1 structure is folded in two well defined modules, one responsible for anchoring to the pneumococcal cell wall and the other, a catalytic module, that hydrolyzes the PG. Conformational rearrangement of Tyr-127 is a critical event in molecular recognition of a stretch of five saccharide rings of the polymeric peptidoglycan (cell wall). The PG is bound at a stretch of the surface that is defined as the peptidoglycan-binding sites 1 and 2, the juncture of which catalysis takes place. The peptidoglycan-binding site 1 binds to a stretch of three saccharides of the peptidoglycan in a conformation essentially identical to that of the peptidoglycan in solution. In contrast, binding of two peptidoglycan saccharides at the peptidoglycan-binding site 2 introduces a kink into the solution structure of the peptidoglycan, en route to catalytic turnover. These findings provide the first structural evidence on recognition of the peptidoglycan and shed light on the discrete events of cell wall degradation by Cpl-1.

P-Coumaric Acid Decarboxylase from Lactobacillus Plantarum: Structural Insights Into the Active Site and Decarboxylation Catalytic Mechanism.

p‐Coumaric acid decarboxylases (PDCs) catalyze the nonoxidative decarboxylation of hydroxycinnamic acids to generate the corresponding vinyl derivatives. Despite the biotechnological relevance of PDCs in food industry, their catalytic mechanism remains largely unknown. Here, we report insights into the structural basis of catalysis for the homodimeric PDC from Lactobacillus plantarum (LpPDC). The global fold of LpPDC is based on a flattened β‐barrel surrounding an internal cavity. Crystallographic and functional analyses of single‐point mutants of residues located within this cavity have permitted identifying a potential substrate‐binding pocket and also to provide structural evidences for rearrangements of surface loops so that they can modulate the accessibility to the active site. Finally, combination of the structural and functional data with in silico results enables us to propose a two‐step catalytic mechanism for decarboxylation of p‐coumaric acid by PDCs where Glu71 is involved in proton transfer, and Tyr18 and Tyr20 are involved in the proper substrate orientation and in the release of the CO2 product. Proteins 2010.

Chagas Disease: Progress and New Perspectives

Chagas disease, also known as American trypanosomiasis, is caused by infection with the protozoan parasite Trypanosoma cruzi. The Pan American Health Organization (PAHO) estimates that currently 7.7 million of people have Trypanosoma cruzi infection in the 21 endemic countries from the southern and southwestern United States to central Argentina and Chile. The only approved therapeutics for the treatment of Chagas disease are two nitroheterocyclic compounds as a nitrofuran (nifurtimox; Lampit) and a nitroimidazole (benznidazole; Rochagan). However, the anti-Trypanosoma cruzi activities of these compounds were discovered empirically over three decades ago. The treatment of Chagas disease with nifurtimox or benznidazole is unsatisfactory because of their limited efficacy in the prevalent chronic stage of the disease and their toxic side effects. In this context, this article will review the current knowledge of the different aspects involved in this illness, such as Trypanosoma cruzi transmission, physiology and biochemistry of the etiological agent, epidemiological aspects and current treatments for American trypanosomiasis. An important section of this review will focus on the different strategies in drug discovery for Chagas disease, including methodology, in vitro screening studies against whole parasites, novel rationally developed approaches on the basis of the increasing knowledge of the biochemistry of Trypanosoma cruzi and the recent progress in the understanding and validation of several targets for the therapy of Chagass disease. A summary of the most relevant drug targets such as sterol biosynthesis pathway, cysteine protease pathway, pyrophosphate metabolism and purine salvage pathway will be reviewed. Moreover, recent studies regarding other strategies currently under development including thiol-dependent redox metabolism, lysophospholipid analogues and DNA binders will also be discussed.

Cannabinoid System in Neurodegeneration: New Perspectives in Alzheimer's Disease

Alzheimers disease is a chronic and progressive neurodegenerative disorder. The presence of functional cannabinoid CB2 receptors in central nervous system (CNS) has provoked that this receptor and its agonist ligands are now considered as promising pharmacological targets for neurological diseases. Herein, we review the evidences supporting the potential role of the ECS as a therapeutic target, focused on CB2 receptor and its ligands, for the treatment of Alzheimers disease.

Neural computational prediction of oral drug absorption based on CODES 2D descriptors

A neural model based on a numerical molecular representation using CODES program to predict oral absorption of any structure is described. This model predicts both high and low-absorbed compounds with a global accuracy level of 74%. CODES/ANN methodology shows promising utilities not only as a conventional in silico tool in high-throughput screening or improvement of absorption capabilities procedures but also the improvement of in vitro-in vivo correlation could be addressed.

Mutagenicity of N-oxide Containing Heterocycles and Related Compounds: Experimental and Theoretical Studies

In the development of new drugs, it is very important to know the effects these may bring to those who consume them. Drugs which act upon certain diseases must not cause toxic side effects on healthy organs. These toxic side effects can be quite varied, i.e. mutagenicity, clastogenicity, teratogenicity, etc., but undoubtedly the mutagenicity officiate in the selection process, during preclinical testing, to advance in clinical trials. Mutagenic compounds are removed and cannot continue its development. There are preclinical studies of mutagenicity and genotoxicity, ranging from in vitro to in vivo studies. Particularly, Ames test is recommended by ICH as the first input in these studies. Herein, we investigated the mutagenicity of an in-house chemical library of eighty five N-oxide containing heterocycles using Ames test in Salmonella thyphimurium TA 98 with and without S9 activation and the use of neural networks in order to predict this nondesired activity. N-oxide containing heterocycles are especially relevant regarding its pharmacological activities as antitrypanosoma, anti-leishmania, anti-tuberculosis, anti-cancer, chemopreventive, anti-inflammatory, anti-atherogenic, and analgesic agents. In some cases, a relationship was found between the presence of N-oxide and mutagenicity. Specifically, benzofuroxan system seems to be responsible for the mutagenicity of certain agents against Chagas disease and certain anti-inflammatory agents. However other N-oxides, such as furoxans with anti-inflammatory and anti-atherosclerosis activities, seem to lack mutagenicity. In other cases, such as quinoxaline dioxides with anti-parasitic activity, mutagenicity shows to be substituent dependent. Applying CODES neural network two models were defined, one without metabolism and other with metabolism. These models predict the mutagenicity with and without metabolism in an excellent manner.

The Use of Ultrasound in the Synthesis of N-Thranilic Acids by the Ullmann Goldberg Reaction

Abstract Ultrasonic irradiation greatly improves the synthesis of N-arylanthranilic acids (shorter reaction times, higher purity of the final products) through the Ullmann Goldberg reaction.

STUDY OF 1-HYDROXYBENZOTRIAZOLE/BENZOTRIAZOLE N-OXIDE TAUTOMERISM IN THE GAS PHASE BY PHOTOELECTRON SPECTROSCOPY

Abstract A photoelectron experimental study of the equilibrium benzotriazole N-oxide/1-hydroxybenzotriazole has demonstrated that only the second compound is present in the gas phase. Moreover, because crystals of each tautomer were used, these experiments prove that tautomeric equilibria can be attained in the gas phase

Synthesis and pharmacological evaluation of sulfamide-based analogues of anandamide.

Arachidonyl and linoleyl sulfamide derivatives have been synthesized and their potential cannabimimetic properties evaluated in in vitro functional and binding assays. Replacement of the ethanolamide moiety of anandamide by -CH(2)NHSO(2)NH-R considerably reduces the CB1 receptor activity and only some of the compounds showed modest cannabinoid properties in binding assays. The new compounds were also tested as inhibitors of the FAAH enzyme but were inactive.