Semi-syntheses and interrogation of indole-substituted Aspidosperma terpenoid alkaloids.

We demonstrated here a series of Aspidosperma terpenoid alkaloids can be quickly prepared using semisynthesis from naturally sourced tabersonine, featuring multiple oxygen-based substituents on the indole ring such as hydroxy and methoxy groups. This panel of complex compounds enabled the exploration of indole modifications to optimize the indole alkaloids' anticancer activity, generating lead compounds (e.g., with C15-hydroxy, C16-methoxy, and/or C17-methoxy derivatizations) that potently inhibit cancer cell line growth in the single-digit micromolar range. These results can help guide the development of Aspidosperma terpenoid alkaloid therapeutics. Furthermore, this synthetic approach features late-stage facile derivatization on complex natural product molecules, providing a versatile path to indole derivatization of this family of alkaloids with diverse chemical functionalities for future medicinal chemistry and chemical biology discoveries.

Comparison of micronuclei frequency between smokers and non-smokers: a systematic review / Comparação da frequência de micronúcleos entre indivíduos fumantes e não fumantes: uma revisão sistemática

ABSTRACT Introduction: Cancer results from the accumulation of several modifications in the genetic material and, therefore, it is possible to carry out its cytogenetic detection using biomarkers. Micronuclei (MN) have been addressed in the literature as biomarkers of genotoxic damage. These markers provide information on biological or biochemical changes in a target tissue at early stage, enabling a favorable prognosis. Objective: To compare whether the frequency of MN in active smokers is higher than that in non-smokers. Material and method: The search was performed in the Medical Literature Analysis and Retrieval System (PubMeb), in the Latin American and Caribbean Literature in Health Sciences (LILACS), and in the Scientific Electronic Electronic Library Online (SciELO), for articles published in the last ten years. Randomized clinical trials, with a cross-sectional design, which compared the MN frequency in the oral mucosa of adult smokers and non-smokers, were selected. Results: A total of 52 articles were identified, four of them were removed due to duplicity. From the remaining 48 studies, after reading their titles and abstracts, 14 remained, which had their full texts read. Finally, eight articles remained for the qualitative analysis. Discussion and conclusion: Individuals who use tobacco present genotoxic and cytotoxic damages that interfere in the mitosis process, which leads to MN formation. The hypothesis of smoking as the cause of this genetic alteration is corroborated by the authors when comparing the data obtained in their studies between risk groups and control groups.

RESUMEN Introducción: El cáncer es el resultado de la acumulación de diversas modificaciones en el material genético, por lo tanto, es posible realizar su detección citogenética usando biomarcadores. Micronúcleos (MN) se han abordado por la literatura como biomarcadores de daño genotóxico. Estos marcadores ofrecen información sobre cambios biológicos o bioquímicos en un tejido diana todavía en forma precoz, permitiendo un pronóstico bueno. Objetivo: Determinar si la frecuencia de MN en fumadores activos es superior a la de los no fumadores. Material y método: Hicimos una búsqueda en Medical Literature Analysis and Retrieval System (PubMeb), Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) y Scientific Eletronic Library On-line (SciELO) de artículos publicados en los últimos diez años. Hemos seleccionado ensayos clínicos aleatorizados, de diseño transversal, que compararon la frecuencia de MN en la mucosa bucal de personas adultas fumadoras y no fumadoras. Resultados: Se identificaron 52 artículos; cuatro de ellos fueron eliminados debido a duplicidad. Entre los 48 estudios restantes, tras la lectura de sus títulos y resúmenes, quedaron 14, que tuvieron sus textos completos leídos. Por último, ocho artículos permanecieron para el análisis cualitativo. Discusión y conclusión: Personas que utilizan tabaco presentan daños genotóxicos y citotóxicos que interfieren con el proceso de mitosis, lo que acarrea la formación de MN. La hipótesis del tabaquismo como causa de ese cambio genético es corroborada por los autores al cotejar los datos obtenidos en sus estudios entre grupos de riesgo y grupos de control.

RESUMO Introdução: O câncer é o resultado do acúmulo de diversas modificações no material genético, portanto, é possível realizar sua detecção citogenética utilizando biomarcadores. Micronúcleos (MN) têm sido abordados pela literatura como biomarcadores de danos genotóxicos. Esses marcadores fornecem informações sobre alterações biológicas ou bioquímicas em um tecido-alvo ainda de forma precoce, possibilitando um prognóstico favorável. Objetivo: Comparar se a frequência de MN em indivíduos fumantes ativos é superior à dos não fumantes. Material e método: Realizou-se a busca no Medical Literature Analysis and Retrieval System (PubMeb), no Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) e no Scientific Eletronic Library On-line (SciELO) de artigos publicados nos últimos dez anos. Foram selecionados ensaios clínicos randomizados, com delineamento transversal, que compararam a frequência de MN na mucosa bucal de indivíduos adultos fumantes e não fumantes. Resultados: Cinquenta e dois artigos foram identificados; quatro deles foram removidos devido à duplicidade. Dos 48 estudos restantes, após a leitura dos seus títulos e resumos, restaram 14, os quais tiveram seus textos completos lidos. Por fim, oito artigos permaneceram para a análise qualitativa. Discussão e conclusão: Indivíduos que utilizam tabaco apresentam danos genotóxicos e citotóxicos que interferem no processo de mitose, o que acarreta a formação de MN. A hipótese do tabagismo como causa dessa alteração genética é corroborada pelos autores ao confrontar os dados obtidos em seus estudos entre grupos de risco e grupos-controle.

Elucidating the inhibition of peptidoglycan biosynthesis in Staphylococcus aureus by albocycline, a macrolactone isolated from Streptomyces maizeus.

Antibiotic resistance is a serious threat to global public health, and methicillin-resistant Staphylococcus aureus (MRSA) is a poignant example. The macrolactone natural product albocycline, derived from various Streptomyces strains, was recently identified as a promising antibiotic candidate for the treatment of both MRSA and vancomycin-resistant S. aureus (VRSA), which is another clinically relevant and antibiotic resistant strain. Moreover, it was hypothesized that albocycline's antimicrobial activity was derived from the inhibition of peptidoglycan (i.e., bacterial cell wall) biosynthesis. Herein, preliminary mechanistic studies are performed to test the hypothesis that albocycline inhibits MurA, the enzyme that catalyzes the first step of peptidoglycan biosynthesis, using a combination of biological assays alongside molecular modeling and simulation studies. Computational modeling suggests albocycline exists as two conformations in solution, and computational docking of these conformations to an ensemble of simulated receptor structures correctly predicted preferential binding to S. aureus MurA-the enzyme that catalyzes the first step of peptidoglycan biosynthesis-over Escherichia coli (E. coli) MurA. Albocycline isolated from the producing organism (Streptomyces maizeus) weakly inhibited S. aureus MurA (IC50 of 480 µM) but did not inhibit E. coli MurA. The antimicrobial activity of albocycline against resistant S. aureus strains was superior to that of vancomycin, preferentially inhibiting Gram-positive organisms. Albocycline was not toxic to human HepG2 cells in MTT assays. While these studies demonstrate that albocycline is a promising lead candidate against resistant S. aureus, taken together they suggest that MurA is not the primary target, and further work is necessary to identify the major biological target.

A BAHD acyltransferase catalyzing 19-O-acetylation of tabersonine derivatives in roots of Catharanthus roseus enables combinatorial synthesis of monoterpene indole alkaloids.

While the characterization of the biosynthetic pathway of monoterpene indole alkaloids (MIAs) in leaves of Catharanthus roseus is now reaching completion, only two enzymes from the root counterpart dedicated to tabersonine metabolism have been identified to date, namely tabersonine 19-hydroxylase (T19H) and minovincine 19-O-acetyltransferase (MAT). Albeit the recombinant MAT catalyzes MIA acetylation at low efficiency in vitro, we demonstrated that MAT was inactive when expressed in yeast and in planta, suggesting an alternative function for this enzyme. Therefore, through transcriptomic analysis of periwinkle adventitious roots, several other BAHD acyltransferase candidates were identified based on the correlation of their expression profile with T19H and found to localize in small genomic clusters. Only one, named tabersonine derivative 19-O-acetyltransferase (TAT) was able to acetylate the 19-hydroxytabersonine derivatives from roots, such as minovincinine and hörhammericine, following expression in yeast. Kinetic studies also showed that the recombinant TAT was specific for root MIAs and displayed an up to 200-fold higher catalytic efficiency than MAT. In addition, gene expression analysis, protein subcellular localization and heterologous expression in Nicotiana benthamiana were in agreement with the prominent role of TAT in acetylation of root-specific MIAs, thereby redefining the molecular determinants of the root MIA biosynthetic pathway. Finally, identification of TAT provided a convenient tool for metabolic engineering of MIAs in yeast enabling efficiently mixing different biosynthetic modules spatially separated in the whole plant. This combinatorial synthesis associating several enzymes from Catharanthus roseus resulted in the conversion of tabersonine in tailor-made MIAs bearing both leaf and root-type decorations.

Subchronic treatment with acai frozen pulp prevents the brain oxidative damage in rats with acute liver failure.

Acai has been used by the population due to its high nutritional value and its benefits to health, such as its antioxidant properties. The aim of this study was to evaluate the protective effect of acai frozen pulp on oxidative stress parameters in cerebral cortex, hippocampus and cerebellum of Wistar rats treated with carbon tetrachloride (CCl4). Thirty male Wistar rats (90-day-old) were orally treated with water or acai frozen pulp for 14 days (7 µL/g). On the 15th day, half of the animals received treatment with mineral oil and the other half with CCl4 (3.0 mL/kg). The cerebral cortex, hippocampus and cerebellum were dissected and used for analysis of creatine kinase activity (CK), thiobarbituric acid reactive substances (TBARS), carbonyl, sulfhydryl, and the activity of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Statistical analysis was performed by ANOVA followed by Tukey's post-test. CCl4 was able to inhibit CK activity in all tissues tested and to provoke lipid damage in cerebral cortex and cerebellum, and protein damage in the three tissues tested. CCl4 enhanced CAT activity in the cerebral cortex, and inhibited CAT activity in the hippocampus and cerebellum and reduced SOD activity in all tissues studied. Acai frozen pulp prevented the inhibition of CK, TBARS, carbonyl and CAT activity in all brain structures and only in hippocampus for SOD activity. Therefore, acai frozen pulp has antioxidant properties and maybe could be useful in the treatment of some diseases that affect the central nervous system that are associated with oxidative damage.

Synthesis and biological evaluation of pentacyclic strychnos alkaloids as selective modulators of the ABCC10 (MRP7) efflux pump.

The selective modulation of ATP-binding cassette (ABC) efflux pumps overexpressed in multidrug resistant cancers (MDR) and attendant resensitization to chemotherapeutic agents represent a promising strategy for treating cancer. We have synthesized four novel pentacyclic Strychnos alkaloids alstolucines B (2), F (3), and A (5) and N-demethylalstogucine (4), in addition to known Strychnos alkaloid echitamidine (16), and we evaluated compounds 1-5 in biochemical assays with ABCC10 and P-glycoprotein (P-gp). Alstolucines B (2) and F (3) inhibited ABCC10 ATPase activity at 12.5 µM without affecting P-gp function; moreover, they resensitized ABCC10-transfected cell lines to paclitaxel at 10 µM. Altogether, the alstolucines represent promising lead candidates in the development of modulators of ABCC10 for MDR cancers overexpressing this pump.

Effect of physical exercise on changes in activities of creatine kinase, cytochrome c oxidase and ATP levels caused by ovariectomy.

The reduction in the secretion of ovarian hormones, principally estrogen, is a consequence of menopause. Estrogens act primarily as female sex hormones, but also exert effects on different physiological systems including the central nervous system. The treatment normally used to reduce the symptoms of menopause is the hormone therapy, which seems to be effective in treating symptoms, but it may be responsible for adverse effects. Based on this, there is an increasing demand for alternative therapies that minimize signs and symptoms of menopause. In the present study we investigated the effect of ovariectomy and/or physical exercise on the activities of energy metabolism enzymes, such as creatine kinase (cytosolic and mitochondrial fractions), pyruvate kinase, succinate dehydrogenase, complex II, cytochrome c oxidase, as well as on ATP levels in the hippocampus of adult rats. Adult female Wistar rats with 90 days of age were subjected to ovariectomy (an animal model widely used to mimic the postmenopausal changes). Thirty days after the procedure, the rats were submitted to the exercise protocol, which was performed three times a week for 30 days. Twelve hours after the last training session, the rats were decapitated for subsequent biochemical analyzes. Results showed that ovariectomy did not affect the activities of pyruvate kinase, succinate dehydrogenase and complex II, but decreased the activities of creatine kinase (cytosolic and mitochondrial fractions) and cytochrome c oxidase. ATP levels were also reduced. Exercise did not produce the expected results since it was only able to partially reverse the activity of creatine kinase cytosolic fraction. The results of this study suggest that estrogen deficiency, which occurs as a result of ovariectomy, affects generation systems and energy homeostasis, reducing ATP levels in hippocampus of adult female rats.

Synthesis and evaluation of Strychnos alkaloids as MDR reversal agents for cancer cell eradication.

Natural products represent the fourth generation of multidrug resistance (MDR) reversal agents that resensitize MDR cancer cells overexpressing P-glycoprotein (Pgp) to cytotoxic agents. We have developed an effective synthetic route to prepare various Strychnos alkaloids and their derivatives. Molecular modeling of these alkaloids docked to a homology model of Pgp was employed to optimize ligand-protein interactions and design analogues with increased affinity to Pgp. Moreover, the compounds were evaluated for their (1) binding affinity to Pgp by fluorescence quenching, and (2) MDR reversal activity using a panel of in vitro and cell-based assays and compared to verapamil, a known inhibitor of Pgp activity. Compound 7 revealed the highest affinity to Pgp of all Strychnos congeners (Kd=4.4µM), the strongest inhibition of Pgp ATPase activity, and the strongest MDR reversal effect in two Pgp-expressing cell lines. Altogether, our findings suggest the clinical potential of these synthesized compounds as viable Pgp modulators justifies further investigation.

Conformationally constrained functional peptide monolayers for the controlled display of bioactive carbohydrate ligands.

In this study, we employed thiolated peptides of the conformationally constrained, strongly helicogenic α-aminoisobutyric acid (Aib) residue to prepare self-assembled monolayers (SAMs) on gold surfaces. Electrochemistry and infrared reflection absorption spectroscopy support the formation of very well packed Aib-peptide SAMs. The immobilized peptides retain their helical structure, and the resulting SAMs are stabilized by a network of intermolecular H bonds involving the NH groups adjacent to the Au surface. Binary SAMs containing a synthetically defined glycosylated mannose-functionalized Aib-peptide as the second component display similar features, thereby providing reproducible substrates suitable for the controlled display of bioactive carbohydrate ligands. The efficiency of such Aib-based SAMs as a biomolecular recognition platform was evidenced by examining the mannose-concanavalin A interaction via surface plasmon resonance biosensing.

Homocysteine induces energy imbalance in rat skeletal muscle: is creatine a protector?

Homocystinuria is a neurometabolic disease caused by a severe deficiency of cystathionine beta-synthase activity, resulting in severe hyperhomocysteinemia. Affected patients present several symptoms including a variable degree of motor dysfunction. In this study, we investigated the effect of chronic hyperhomocysteinemia on the cell viability of the mitochondrion, as well as on some parameters of energy metabolism, such as glucose oxidation and activities of pyruvate kinase, citrate synthase, isocitrate dehydrogenase, malate dehydrogenase, respiratory chain complexes and creatine kinase in gastrocnemius rat skeletal muscle. We also evaluated the effect of creatine on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injections of homocysteine (0.3-0.6 µmol/g body weight) and/or creatine (50 mg/kg body weight) from the 6th to the 28th days of age. The animals were decapitated 12 h after the last injection. Homocysteine decreased the cell viability of the mitochondrion and the activities of pyruvate kinase and creatine kinase. Succinate dehydrogenase was increased other evaluated parameters were not changed by this amino acid. Creatine, when combined with homocysteine, prevented or caused a synergistic effect on some changes provoked by this amino acid. Creatine per se or creatine plus homocysteine altered glucose oxidation. These findings provide insights into the mechanisms by which homocysteine exerts its effects on skeletal muscle function, more studies are needed to elucidate them. Although creatine prevents some alterations caused by homocysteine, it should be used with caution, mainly in healthy individuals because it could change the homeostasis of normal physiological functions.