Gildardo Rivera

Recent advances in antitubercular natural products

Currently, one third of the worlds population is infected with Mycobacterium tuberculosis and 8.9-9.9 million new and relapse cases of tuberculosis are reported every year. The emergence of new cases, the increased incidence of multi-drug resistant strains of M. tuberculosis, and the adverse effects of first- and second-line antituberculosis drugs have led to renewed research interest in natural products in the hope of discovering new antitubercular leads. Interestingly, hundreds of natural products, possessing novel, uncommon, and known structural architectures, have been reported to exhibit activity towards non-resistant and multi-drug resistant strains of M. tuberculosis. The present review covers literature published during the last five years about those naturally occurring compounds with reported growth inhibitory activity in vitro towards sensitive and resistant M. tuberculosis strains. Compounds with antitubercular properties at minimal inhibitory concentrations (MICs) of less than 50 μg/mL or 60 μM were selected and grouped according to their source of origin (plants, bacteria, fungi, marine organisms, etc) and chemical type (terpenes, steroids, alkaloids, flavonoids, poliketides, peptides, etc). In some cases, the selection covers those structurally relevant natural products with low bioactivity (MICs of ≤128 μg/mL), and also those semisynthetic derivatives with remarkable antitubercular activity (MICs of ≤10 μg/mL). Additionally, this review includes a special section for those natural products that specifically target genes or enzymes of M. tuberculosis.

Recent Advances in Medicinal Chemistry of Sulfonamides. Rational Design as Anti-Tumoral, Anti-Bacterial and Anti-Inflammatory Agents

Now-a-days, cancer is becoming one of the major problems of public health in the world. Pharmacology treatment is a way to increase quality and long life. Predominantly, in last decade sulfonamide derivatives have been described as potential carbonic anhydrase inhibitors. In the present work, we describe recent advances during the last decade in medicinal chemistry of sulfonamides derivatives with some examples of rational design as anti-tumoral, antibacterial and anti-inflammatory agents. We show strategy design, structure-activity relationship, biological activity and advances of new sulfonamide compounds that have more health significance than some clinically used sulfonamides.

Melanin-Concentrating Hormone Receptor 1 Antagonists: A New Perspective for the Pharmacologic Treatment of Obesity

Obesity is a chronic disease characterized by the accumulation of excess adipose tissue associated with an increased risk of multiple morbidities and mortality. At the present time, only three drugs have been approved by the Food and Drug Administration (FDA) for the treatment of obesity. Agonists and antagonists of some of the substances implicated in the regulation of energy homeostasis represent opportunities for anti-obesity drug development. The most promising targets are alpha-melanocyte stimulating hormone (alpha-MSH) receptors, cannabinoid receptors, the 5-hydroxytryptamine (5-HT) receptors and melanin-concentrating hormone (MCH) receptors. MCH receptors could be major potential targets for the treatment of obesity. Many pharmaceutical companies have described MCH-R1 antagonists that have appeared over the past year. Recently, two compounds went into phase I clinical trials that evaluate MCH receptor antagonists as a new perspective for the pharmacologic treatment of obesity. In this review, structure-activity relationships (SAR) in the development of MCH-R1 antagonists are provided.

Anticancer drug design using scaffolds of β-lactams, sulfonamides, quinoline, quinoxaline and natural products. Drugs advances in clinical trials.

Eleven years after the start of a new millennium characterized by amazing scientific development, the cure for cancer remains a major challenge for humanity. In this regard, scientific efforts have focused on the search for new therapeutic targets that involve specific recognition and stop the spread of cancer cells, as well as the development of new therapeutic options that show greater specificity and better therapeutic efficacy. This review includes recent published literature about new anticancer drug design using scaffolds of β-lactams, sulfonamides, quinoline, quinoxaline and natural products, and focuses on the structure-activity relationships of scaffolds that have been reported to potently inhibit cell growth of human tumor cell lines. It describes not only those synthetic or natural compounds aimed at specific molecular targets of cancer cells in vitro, but also compounds currently in clinical trials.

New therapeutic targets for drug design against Trypanosoma cruzi, advances and perspectives.

Chagas disease is one of the most important parasitic diseases in Latin America, affecting 16 to 18 million people. Nifurtimox and Benznidazol are drugs that are commonly used in its treatment; however, these drugs produce several adverse reactions and are not effective in the chronic phase of the disease. Therefore, the design, synthesis, and biological evaluation of new compounds with potential activity against Trypanozoma cruzi are of great importance. We review six proteins involved in the biochemical metabolism of Trypanosoma cruzi that have recently been studied as potential targets for designing new drugs for Chagas disease. These are farnesyl pyrophosphate synthase, trans-sialidase, cruzain cystein protease, trypanothione reductase, glucose 6-phosphate-dehydrogenase, glyceraldehyde 3-phosphate-dehydrogenase, and alpha-hydroxy acid dehydrogenase. We also review the advances of compounds recently designed based on structure-activity, and the perspectives of new compounds that inhibit these therapeutic targets.

New 2-benzylsulfanyl-nicotinic acid based 1,3,4-oxadiazoles: Their synthesis and biological evaluation

A novel series of 5-(2-benzylsulfanyl-pyridin-3-yl)-2-(substituted)-sulfanyl-1,3,4-oxadiazoles 6a-j were synthesized from key intermediate 5-(2-benzylsulfanyl-pyridin-3-yl)-3H-[1,3,4]oxadiazole-2-thione 5. Nucleophilic substitution reactions with different electrophiles (E+), such as haloacetate and haloalkyl groups, were performed to get target compounds 6a-j. Compounds were characterized by NMR, mass, IR spectra and C, H, N analyses. All compounds were evaluated for their antimicrobial and antimycobacterial activities; selected analogs were screened for their anticancer activity on 60 tumor cell lines at single dose 1.00(-5) M. Unfortunately, none of the compounds showed a significant antitumor activity on 60 human tumor cell lines. However, compounds 6g and 6f with benzothiazole moiety (12.5 and 25 μg/ml) showed promising activity against Escherichia coli compared to ampicillin; compounds 6d, 6j bearing triazole and morpholine, respectively, showed promising antitubercular activity (25 μg/ml) compared to rifampicin.

Traditional plants as source of functional foods: a review.

The aim of this work was to assess the following plants as functional foods that can be found in Mexico: white sapote (Casimiroa edulis), jicama (Pachyrhizus spp.), amaranth (Amaranthus hypochondriacus), sweet fennel (Foeniculum vulgare), oregano (Lippia graveolens), pitahaya (Hylocereus sp.), agave (Agave americana), pelitre (Heliopsis longipes), and purslane (Portulaca oleracea L). The main characteristics, components and active substances, forms of use in traditional medicine, nutritional properties, evaluation of biological assays, and the potential possibilities of research with the plants and/or extracts were reviewed.

The bioactivity of plant extracts against representative bacterial pathogens of the lower respiratory tract

BackgroundLower respiratory tract infections are a major cause of illness and death. Such infections are common in intensive care units (ICU) and their lethality persists despite advances in diagnosis, treatment and prevention. In Mexico, some plants are used in traditional medicine to treat respiratory diseases or ailments such as cough, bronchitis, tuberculosis and other infections. Medical knowledge derived from traditional societies has motivated searches for new bioactive molecules derived from plants that show potent activity against bacterial pathogens. Therefore, the aim of this study was to evaluate the effect of hexanic, chloroformic (CLO), methanolic (MET) and aqueous extracts from various plants used in Mexican traditional medicine on various microorganisms associated with respiratory disease.Methodsthirty-five extracts prepared from nine plants used in Mexican traditional medicine for the treatment of respiratory infections were evaluated against 15 control bacterial species and clinical isolates.ResultsBoth chloroformic (CLO) and methanolic (MET) extracts of Larrea tridentata were active against Methicillin-resistant S. aureus, B. subtilis and L. monocytogenes. A MET extract of L. tridentata was also active against S. aureus, S. pneumoniae, S. maltophilia, E. faecalis and H. influenzae and the CLO extract was active against A. baumannii. An Aqueous extract of M. acumitata and a MET extract of N. officinale were active against S. pneumoniae. CLO and MET extracts of L. tridentata were active against clinical isolates of S. aureus, S. pneumoniae and E. faecalis.ConclusionOverall, our results support the potential use of L. tridentata as a source of antibacterial compounds.

A pyrosequencing method for molecular monitoring of regions in the inhA, ahpC and rpoB genes of Mycobacterium tuberculosis

In this study, a pyrosequencing method for monitoring two genes related to isoniazid (INH)-resistance and a region of the rpoB gene linked to rifampin (RMP)-resistance in Mycobacterium tuberculosis was developed and evaluated. Specifically, a 20-base pair (bp) region of inhA (from -24 to -4), a 35-bp region of ahpC (from -39 to -4), and a 57-bp region of rpoB (from codon 515 to 533) were analysed by pyrosequencing. For the development of the method, selected non-consecutive clinical isolates of M. tuberculosis were analysed, including: 25 isolates susceptible to both INH and RMP, 18 RMP-monoresistant isolates, 17 INH-monoresistant isolates, and 15 multidrug-resistant strains. Our pyrosequencing methodology was further evaluated using 96 M. tuberculosis isolates. Mutations in ahpC were found to be associated with INH resistance (p <0.05). By setting any mutation in ahpC as a marker of resistance, the specificity and the positive predictive value (PPV) were 100%. Similarly, any mutation in the rpoB gene was associated with a RMP resistance phenotype (p <0.01). Using any mutation in rpoB as a marker of RMP resistance, the sensitivity of this assay was 73% and the specificity and PPV were 100%. The use of this pyrosequencing method to analyse the ahpC and rpoB genes allowed us to detect INH- and/or RMP-resistant isolates. Furthermore, this method represents an opportunity to expedite the description of novel mutations related to drug resistance.

Anti-Trypanosoma cruzi and anti-leishmanial activity by quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives

In this work, a novel series of ethyl and methyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives were evaluated in vitro on Trypanosoma cruzi trypomastigotes and Leishmania mexicana promastigotes, and cytotoxicity activity in murine macrophages was tested. In silico molecular docking simulations of trypanothione reductase were also done. Three compounds of 33 quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives showed better anti-T. cruzi activity than nifurtimox and beznidazole; two compounds had better anti-leishmanial activity that amphotericin-B, and two compounds showed better activity against both parasites than reference drugs. Compounds M2, M7, M8 and E5, showed low cytotoxic activity on the host cell. The in silico studies suggest that compound M2 is a potential trypanothione reductase inhibitor.