Synthesis, antioxidant activity and structure-activity relationships for a new series of 2-(N-acylaminoethyl)indoles with melatonin-like cytoprotective activity

Enhanced anti-angiogenic activity of novel melatonin-like agents

Hypoxia-inducible factor-1 (HIF-1) plays an important role in cellular responses to hypoxia, including the transcriptional activation of several genes involved in tumor angiogenesis. Melatonin, also known as N-acetyl-5-methopxytryptamine, is produced naturally by the pineal gland and has anti-angiogenic effects in cancer through its ability to modulate HIF-1α activity. However, the use of melatonin as a therapeutic is limited by its low oral bioavailability and short half-life. Here, we synthesized melatonin-like molecules with enhanced HIF-1α targeting activity and less toxicity and investigated their effects on tumor growth and angiogenesis, as well as the underlying molecular mechanisms. Among melatonin derivatives, N-butyryl-5-methoxytryptamine (NB-5-MT) showed the most potent HIF-1α targeting activity. This molecule was able to (a) reduce the expression of HIF-1α at the protein level, (b) reduce the transcription of HIF-1α target genes, (c) reduce reactive oxygen species (ROS) generation, (d) decrease angiogenesis in vitro and in vivo, and (e) suppress tumor size and metastasis. In addition, NB-5-MT showed improved anti-angiogenic activity compared with melatonin due to its enhanced cellular uptake. NB-5-MT is thus a promising lead for the future development of anticancer compounds with HIF-1α targeting activity. Given that HIF-1α is overexpressed in the majority of human cancers, the melatonin derivative NB-5-MT could represent a novel potent therapeutic agent for cancer.

Tryptophan Derivatives by Saccharomyces cerevisiae EC1118: Evaluation, Optimization, and Production in a Soybean-Based Medium

Given the pharmacological properti es and the potential role of kynurenic acid (KYNA) in human physiology and the pleiotropic activity of the neurohormone melatonin (MEL) involved in physiological and immunological functions and as regulator of antioxidant enzymes, this study aimed at evaluating the capability of Saccharomyces cerevisiae EC1118 to release tryptophan derivatives (dTRPs) from the kynurenine (KYN) and melatonin pathways. The setting up of the spectroscopic and chromatographic conditions for the quantification of the dTRPs in LC-MS/MS system, the optimization of dTRPs' production in fermentative and whole-cell biotransformation approaches and the production of dTRPs in a soybean-based cultural medium naturally enriched in tryptophan, as a case of study, were included in the experimental plan. Variable amounts of dTRPs, with a prevalence of metabolites of the KYN pathway, were detected. The LC-MS/MS analysis showed that the compound synthesized at highest concentration is KYNA that reached 9.146 ± 0.585 mg/L in fermentation trials in a chemically defined medium at 400 mg/L TRP. Further experiments in a soybean-based medium confirm KYNA as the main dTRPs, whereas the other dTRPs reached very lower concentrations. While detectable quantities of melatonin were never observed, two MEL isomers were successfully measured in laboratory media.

Microorganisms: Producers of Melatonin in Fermented Foods and Beverages

Melatonin has recently been detected in fermented beverages and foods, in which microorganism metabolism is highly important. The existing literature knowledge discusses the direction for future studies in this review. Evidence shows that many species of microorganisms could synthesize melatonin. However, the actual concentrations of melatonin in fermented foods and beverages range from picograms per milliliter to nanograms per milliliter. Different types of microorganisms, different raw materials, different culture environments, the presence or absence of precursors, high or low alcohol content, and different detection methods are all possible reasons for the huge difference of melatonin levels. Thus far, there have been relatively few studies on the melatonin synthesis pathway microorganisms. Thus, referring to the synthetic pathway of plants and animals, the putative melatonin biosynthesis pathway of microorganisms is presented. It will be significant to discuss whether all species of microorganisms have the capacity to synthesize melatonin and what the biological functions of melatonin are in microorganisms. Melatonin plays a lot of important roles in microorganisms, particularly in enhancing the tolerance of environment stress. Also, the loss of melatonin concentration in commercially available fermented foods and beverages is a ubiquitous trend, and how to solve this problem is a new field to be further explored.

Assessment of Tryptophan, Tryptophan Ethylester, and Melatonin Derivatives in Red Wine by SPE-HPLC-FL and SPE-HPLC-MS Methods

Melatonin (MEL) is an indoleamine produced mainly by the pineal gland in vertebrates. It plays a significant role in the regulation of circadian rhythms, mitigation of sleeping disorders, and jet lag. This compound is synthetized from tryptophan (TRP) and it has been found in seeds, fruits, and fermented beverages, including wine. Wine is also a source of other tryptophan derivatives, the tryptophan ethylester (TEE) and MEL isomers (MISs), for which the biological properties need to be elucidated. An analytical method for the simultaneous quantification of TRP, TEE, and MEL was developed by a Solid Phase Extraction (SPE) of a preconcentration of wine followed by high performance liquid chromatography (HPLC) analysis either with fluorescence or mass spectrometer detectors. The analytical method showed a relative standard deviation (RSD) lower than 8%, except for TRP (RSD 10.5% in wine). The recovery was higher than 76%. The versatility of SPE preconcentrations allowed for the adequate preconcentration of wine sample as well as detection of low concentrations, an important aspect especially for MEL (detection limit 0.0023 µg/L). The proposed method proved to be suitable for assessing the investigated compounds in some red wine samples, where 74.4⁻256.2 µg/L and 0.038⁻0.063 µg/L of TEE and MEL were detected, respectively. Five MISs were also found in wine samples in concentrations up to 1.97 µg/L.

Il contributo dei batteri lattici per la presenza di melatonina nel vino rosso

La melatonina (MEL) è un'indolammina implicata nella regolazione dei cicli circadiani e che possiede attività antiossidante. La presenza di MEL è stata dimostrata nelle piante e negli alimenti con particolare attenzione agli alimenti e bevande fermentati, tra cui il vino. L'uva è una fonte di MEL e nel vino l'attività metabolica del lievito svolge un ruolo cruciale per la produzione di MEL. È stato recentemente suggerito che anche i batteri lattici (LAB) posseggano tale abilità. In questo studio è stata indagata la sintesi di MEL da parte dei LAB in condizioni enologiche e di laboratorio. Sono stati analizzati 8 vini rossi prodotti su scala industriale in 4 cantine. Inoltre, 11 ceppi di LAB sono stati inoculati in terreno sintetico simil-vino. Dai risultati ottenuti è emerso che nei vini prodotti in due delle quattro cantine è stato osservato un aumento di MEL al termine della fermentazione malolattica. Tutti i ceppi oggetto dello studio hanno prodotto MEL in condizioni di laboratorio in quantità variabile a seconda del ceppo. I risultati mettono in evidenza per la prima volta che i LAB sono capaci di rilasciare MEL sia in condizioni di laboratorio che nel vino prodotto industrialmente. The contribution of lactic bacteria on melatonin in red wine

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Substrate-Controlled Transformation of Azobenzenes to Indazoles and Indoles via Rh(III)-Catalysis

Rh(III)-catalyzed substrate-controlled transformation of azobenzenes to indazoles and 2-acyl (NH) indoles is achieved via C-H functionalization. Generally, good functional groups tolerance, satisfying yields, and excellent regio-selectivity are achieved in this reaction. Mechanistically, the reaction with acrylates undergoes β-hydride elimination, while the reaction with vinyl ketones or acrylamides undergoes nucleophilic addition. Copper acetate was supposed to play different roles in the β-hydride elimination to furnish indazoles and nucleophilic addition of C-Rh bond to deliver 2-acyl (NH) indoles.

Ultrahigh-Performance Liquid Chromatography (UHPLC)-Tandem Mass Spectrometry (MS/MS) Quantification of Nine Target Indoles in Sparkling Wines

An ultrahigh-performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) method was developed for the simultaneous determination of nine target indoles in sparkling wines. The proposed method requires minimal sample pretreatment, and its performance parameters (accuracy, repeatability, LOD, and matrix effect) indicate that it is suitable for routine analysis. Four indoles were found at detectable levels in commercial Cava samples: 5-methoxytryptophol (5MTL), tryptophan (TRP), tryptophan ethyl ester (TEE), and N-acetylserotonin (NSER). Two of them, NSER and 5MTL, are reported here for the first time in sparkling wines, with values of 0.3-2 and 0.29-29.2 μg/L, respectively. In the same samples, the contents of melatonin (MEL), serotonin (SER), 5-hydroxytryptophan (5-OHTRP), 5-hydroxyindole-3-acetic acid (5OHIA), and 5-methoxy-3-indoleacetic acid (5MIA) were all below the corresponding limits of detection.

Fundamental issues related to the origin of melatonin and melatonin isomers during evolution: relation to their biological functions

Melatonin and melatonin isomers exist and/or coexist in living organisms including yeasts, bacteria and plants. The levels of melatonin isomers are significantly higher than that of melatonin in some plants and in several fermented products such as in wine and bread. Currently, there are no reports documenting the presence of melatonin isomers in vertebrates. From an evolutionary point of view, it is unlikely that melatonin isomers do not exist in vertebrates. On the other hand, large quantities of the microbial flora exist in the gut of the vertebrates. These microorganisms frequently exchange materials with the host. Melatonin isomers, which are produced by these organisms inevitably enter the host's system. The origins of melatonin and its isomers can be traced back to photosynthetic bacteria and other primitive unicellular organisms. Since some of these bacteria are believed to be the precursors of mitochondria and chloroplasts these cellular organelles may be the primary sites of melatonin production in animals or in plants, respectively. Phylogenic analysis based on its rate-limiting synthetic enzyme, serotonin N-acetyltransferase (SNAT), indicates its multiple origins during evolution. Therefore, it is likely that melatonin and its isomer are also present in the domain of archaea, which perhaps require these molecules to protect them against hostile environments including extremely high or low temperature. Evidence indicates that the initial and primary function of melatonin and its isomers was to serve as the first-line of defence against oxidative stress and all other functions were acquired during evolution either by the process of adoption or by the extension of its antioxidative capacity.

Theoretical insight into the antioxidant properties of melatonin and derivatives

Density functional theory calculations on melatonin, metabolites and synthetic derivatives thereof, and a range of other biological antioxidant molecules are presented, with a view to understanding the antioxidant ability of these molecules. After testing of the necessary calculations, we show that melatonin lies close to vitamin E on a donor-acceptor map, indicating that it should be an excellent electron donor but a poor acceptor. The neutral radical metabolite of melatonin is predicted to be an even better donor, whereas other metabolites and synthetic derivatives should retain antioxidant ability but are less powerful than the parent. QSAR models of antioxidant activity, measured in two different assays, are presented. We show that octanol-water partition coefficient is an excellent predictor of activity in lipophilic media, while properties related to electron donor/acceptor power give good fits against activity in aqueous media.

Formation of melatonin and its isomer during bread dough fermentation and effect of baking

Melatonin is produced mainly by the pineal gland in vertebrates. Also, melatonin and its isomer are found in foods. Investigating the formation of melatonin and its isomer is of importance during bread dough fermentation and its degradation during baking since bread is widely consumed in high amounts. Formation of melatonin was not significant during dough fermentation. The melatonin isomer content of nonfermented dough was found to be 4.02 ng/g and increased up to 16.71 ng/g during fermentation. Lower amounts of isomer in crumb and crust than dough showed that the thermal process caused a remarkable degree of degradation in melatonin isomer. At the end of the 180 min fermentation Trp decreased by 58%. The results revealed for the first time the formation of a melatonin isomer in bread dough during yeast fermentation.

Determination of melatonin and its isomer in foods by liquid chromatography tandem mass spectrometry

This study aimed to develop a reliable analytical method for the determination of melatonin and its isomers in various food products. The method entails ethanol extraction of solid samples (or dilution of liquid samples) prior to liquid chromatography coupled to triple quadruple mass spectrometry (LC-MS/MS) analysis of target analytes. The method was in-house validated and successfully applied to various food matrices. Recovery of melatonin from different matrices were found to be 86.0 ± 3.6%, 76.9 ± 5.4%, 98.6 ± 6.4%, and 67.0 ± 4.5% for beer, walnut, tomato and sour cherry samples, respectively. No melatonin could be detected in black and green tea, sour cherry, sour cherry concentrate, kefir (a fermented milk drink) and red wine while the highest amount of melatonin (341.7 ± 29.3 pg/g) was detected in crumb. The highest amounts of melatonin isomer were detected in yeast-fermented foods such as 170.7 ± 29.9 ng/ml in red wine, 14.3 ± 0.48 ng/ml in beer, and 15.7 ± 1.4 ng/g in bread crumb.

Melatonin, melatonin isomers and stilbenes in Italian traditional grape products and their antiradical capacity

Although polyphenols represent the paradigm of the health-promoting effects ascribed to grape products, recently, attention has been paid to dietary melatonin, significantly present in Mediterranean foods. In this work, we measured melatonin, its isomers, stilbenes (trans- and cis-resveratrol and their glucosides, piceids) and total polyphenols in some different grape products (red, white and dessert wines, grape juices and Modena balsamic vinegars) of distinct Italian areas. We also evaluated their antiradical activity by DPPH(·) and ABTS(·+) assays. For indoleamine analysis, the separation was carried out on a 1.7-μm C18 BEH column and the detection performed by means of mass spectrometry with electrospray ionization in positive ion mode with multiple reaction monitoring. The confirmation of the peak identity was accomplished by injection into the high-resolution system (Orbitrap) using accurate mass measurements (error below 1.0 ppm). Mass spectrometry analyses revealed, for the first time, the presence of melatonin in dessert wines and balsamic vinegars, as well as the occurrence of three different melatonin isomers in grape products.

Emergence of naturally occurring melatonin isomers and their proposed nomenclature

Melatonin was considered to be the sole member of this natural family. The emergence of naturally occurring melatonin isomers (MIs) has opened an exciting new research area. Currently, several MIs have been identified in wine, and these molecules are believed to be synthesized by either yeasts or bacteria. A tentative nomenclature for the MIs is proposed in this article. It will be important to explore whether all organisms have the capacity to synthesize MIs, especially under the conditions of environmental stress. These isomers probably share many of the biological functions of melatonin, but their activities seem to exceed those of melatonin. On basis of the limited available information, it seems that MIs differ in their biosynthetic pathways from melatonin. Especially in those compounds in which the aliphatic side chain is not attached to ring atom 3, the starting material may not be tryptophan. Also, the metabolic pathways of MIs remain unknown. This, therefore, is another promising area of research to explore. It is our hypothesis that MIs would increase the performance of yeasts and probiotic bacteria during the processes of fermentation. Therefore, yeasts producing elevated levels of these isomers might have a superior alcohol tolerance and be able to produce higher levels of alcohol. This can be tested by comparing existing yeast strains differing in alcohol tolerance. Selection for MIs may become a strategy for isolating more resistant yeast and Lactobacillus strains, which can be of interest for industrial alcohol production and quality improvements in bacterially fermented foods such as kimchi.

Synthesis of new indole-2-carboxamide and 3-acetamide derivatives and evaluation their antioxidant properties

In recent years, antioxidant compounds play an important role as a health-protecting factor. Antioxidants protect cells against the damaging effects of reactive oxygen species (ROS). An imbalance between antioxidants and ROS results in oxidative stress, which leads to cellular damage and it is linked to many vital diseases. It was shown that heme oxygenase (HO) provides efficient cytoprotection against oxidative stress. In this study, a series of indole-2-carboxamide and 3-acetamide derivatives was tested for in vitro effects on HO activity and 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition. Among the synthesized compounds, N-[3-(dimethylamino)propyl]-1H-indole-2-carboxamide 3 was found as the most activator of HO and N-(2-(dimethylamino)ethyl)-2-(1H-indol-3-yl)acetamide 8 was found the most potent inhibitor for DPPH at 10(-4) M concentration.

Tryptamine-derived alkaloids from Annonaceae exerting neurotrophin-like properties on primary dopaminergic neurons

N-fatty acyl tryptamines constitute a scarce group of natural compounds mainly encountered in Annonaceous plants. No biological activity was reported so far for these rare molecules. This study investigated the neurotrophic properties of these natural tryptaminic derivatives on dopaminergic (DA) neurons in primary mesencephalic cultures. A structure-activity relationships study led us to precise the role of a nitrogen atom into the aliphatic chain conferring to the compounds a combined neuroprotective and neuritogenic activity in the nanomolar range. The potent antioxidant activity of these natural products seems to be involved in part of their mechanism of action. This study provides the first description of natural neurotrophin mimetics present in Annonaceae extracts, and led to the biological characterization of compounds, which present a potential interest in neurodegenerative diseases such as Parkinson's disease.

Synthesis and evaluation of novel N-H and N-substituted indole-2- and 3-carboxamide derivatives as antioxidants agents

We have previously reported on the synthesis of novel indole derivatives where some compounds showed significant antioxidant activity. Here, we report the synthesis of novel N-H and N-substituted indole-2- and 3-carboxamide derivatives and investigated their antioxidant role in order to identify structural characteristics responsible for activity. Although all compounds showed a strong inhibitory (95-100%) effect on superoxide anion (SOD) only compounds 4, 5 and 6 showed simliar potency for the inhibition of lipid peroxidation (81-94%) which revealed that compounds 4, 5 and 6 possessed highly potent antioxidant properties. Substitution in the 1-position of the indole ring caused the significant differences between the activity results regarding lipid peroxidation inhibition.

Synthesis and Antioxidant Properties of NovelN-H andN-Substituted Propanamide Derivatives

The interest in the application of antioxidants for medical treatment has been growing recently. A lot of evidence has proven the link between the development of human diseases and oxidative stress. Indole derivatives were found to be very effective in protecting against oxidative stress. Recent exciting findings have demonstrated that several indole derivatives (IDs) are strong inhibitors of superoxide anion (SOD) and lipid peroxidation (LP). In this study, a series of novel N-H and N-substituted indole-3-propanamide derivatives (I3PADs) have been prepared and their efficiencies were investigated towards SOD and LP. Among the synthesized I3PADs, compounds 5 and 7-12 significantly inhibited O2*- in the range of 94-100%. In addition, N-H I3PADs showed a stronger inhibitory effect (compounds 1-5, 56-83%) on lipid peroxidation levels than SOD.

Omega-3 fatty acids and antioxidants in neurological and psychiatric diseases: an overview

RATIONALE

Omega-3 fatty acids are known to play a role in nervous system activity, cognitive development, memory-related learning, neuroplasticity of nerve membranes, synaptogenesis and synaptic transmission. The brain is considered abnormally sensitive to oxidative damage, and aging is considered one of the most significant risk factors for degenerative neurological disorders. Recently, clinical trials of several neurodegenerative diseases have increasingly targeted the evaluation of the effectiveness of various antioxidants.

OBJECTIVES

The effects of omega-3 fatty acids and antioxidants on the anatomic and functional central nervous system development and their possible therapeutical use in some neurological and psychiatric pathologies are evaluated.

RESULTS

A number of critical trials have confirmed the benefits of dietary supplementation with omega-3 fatty acids not only in several psychiatric conditions, but also in inflammatory and autoimmune and neurodegenerative diseases. Many evidences indicate that antioxidants are also essential in maintaining a correct neurophysiology.

CONCLUSIONS

Omega-3 fatty acids could be useful in the prevention of different pathologies, such as cardiovascular, psychiatric, neurological, dermatological and rheumatological disorders. A number of studies suggest that antioxidants can prevent the oxidation of various macromolecules such as DNA, proteins, and lipids. The ideal use of antioxidants should be a prophylactic and continue treatment before aging.

Interactions of melatonin and its metabolites with the ABTS cation radical: extension of the radical scavenger cascade and formation of a novel class of oxidation products, C2-substituted 3-indolinones

Melatonin had previously been shown to reduce up to four 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) cation radicals (ABTS*+) via a scavenger cascade ending with N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK). However, when melatonin is added to the reaction system in much lower quantities than ABTS*+, the number of radicals scavenged per melatonin molecule is considerably higher and can attain a value of ten. Under conditions allowing for such a stoichiometry, novel products have been detected which derive from AFMK (1). These were separated by repeated chromatography and the major compounds were characterized by spectroscopic methods, such as mass spectrometry (HPLC-MS, EI-MS and ESI-HRMS), 1H nuclear magnetic resonance (NMR) and 13C NMR, heteronuclear multiple bond connectivity (HMBC) correlations. The identified substances are formed by re-cyclization and represent 3-indolinones carrying the side chain at C2; the N-formyl group can be maintained, but deformylated analogs seem to be also generated, according to MS. The primary product from AFMK (1) is N-(1-formyl-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylidenemethyl)-acetamide (2), which is obtained after purification as E- and Z-isomers (2a, 2b); a secondary product has been identified as N-(1-formyl-2-hydroxy-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylmethyl)-acetamide (3). When H2O2 is added to the ABTS*+ reaction mixture in quantities not already leading to substantial reduction of this radical, compound 3 is isolated as the major product, whereas 2a and 2b are virtually absent. The substances formed differ from all previously known oxidation products which derive from melatonin and are, among these, the first 3-indolinones. Moreover, the aliphatic side chain at C2 is reminiscent of other substances which have been synthesized in the search for melatonin receptor ligands.