The interactions of caffeine with monoamine oxidase

Effect of caffeine-chitosan nanoparticles and α-lipoic acid on the cardiovascular changes induced in rat model of obesity

The current research aims to study the therapeutic efficacy of alpha-lipoic acid (α-LA) and caffeine-loaded chitosan nanoparticles (Caf-CNs) against cardiovascular complications induced by obesity. Rats were divided randomly into: control, high fat diet (HFD) induced obesity rat model, obese rats treated with α-LA and/or Caf-CNs. Triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) as well as activities of lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB) significantly increased in the serum of obese rats. In addition, plasma atherogenic index, atherogenic coefficient and Castelli's risk indices I and II showed a significant increase. Additionally, levels of malondialdehyde (MDA) and nitric oxide (NO) and activity of monoamine oxidase (MAO) were significantly elevated in heart tissues of obese rats. However, cardiac Na+/K+-ATPase and acetylcholinesterase (AchE) activities and reduced glutathione (GSH), serotonin (5-HT), norepinephrine (NE) and dopamine (DA) as well as serum high-density lipoprotein cholesterol (HDL-C) were significantly reduced in obese rats. Treatment with α-LA and/or Caf-CNs ameliorated almost all the biochemical and histopathological alterations caused by obesity. In conclusion, the present data revealed that α-LA and/or Caf-CNs may be an effective therapeutic approach against cardiac complications caused by obesity through their antilipemic, anti-atherogenic, antioxidant, and anti-inflammatory activities.

Therapeutic considerations of bioactive compounds in Alzheimer's disease and Parkinson's disease: Dissecting the molecular pathways

Leading neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by the impairment of memory and motor functions, respectively. Despite several breakthroughs, there exists a lack of disease-modifying treatment strategies for these diseases, as the available drugs provide symptomatic relief and bring along side effects. Bioactive compounds are reported to bear neuroprotective properties with minimal toxicity, however, a detailed elucidation of their modes of neuroprotection is lacking. The review elucidates the neuroprotective mechanism(s) of some of the major phyto-compounds in pre-clinical and clinical studies of AD and PD to understand their potential in combating these diseases. Curcumin, eugenol, resveratrol, baicalein, sesamol and so on have proved efficient in countering the pathological hallmarks of AD and PD. Curcumin, resveratrol, caffeine and so on have reached the clinical phases of these diseases, while aromadendrin, delphinidin, cyanidin and xanthohumol are yet to be extensively explored in pre-clinical phases. The review highlights the need for extensive investigation of these compounds in the clinical stages of these diseases so as to utilize their disease-modifying abilities in the real field of treatment. Moreover, poor pharmacokinetic properties of natural compounds are constraints to their therapeutic yields and this review suggests a plausible contribution of nanotechnology in overcoming these limitations.

Natural products targeting cellular processes common in Parkinson's disease and multiple sclerosis

The hallmarks of Parkinson's disease (PD) include the loss of dopaminergic neurons and formation of Lewy bodies, whereas multiple sclerosis (MS) is an autoimmune disorder with damaged myelin sheaths and axonal loss. Despite their distinct etiologies, mounting evidence in recent years suggests that neuroinflammation, oxidative stress, and infiltration of the blood-brain barrier (BBB) all play crucial roles in both diseases. It is also recognized that therapeutic advances against one neurodegenerative disorder are likely useful in targeting the other. As current drugs in clinical settings exhibit low efficacy and toxic side effects with long-term usages, the use of natural products (NPs) as treatment modalities has attracted growing attention. This mini-review summarizes the applications of natural compounds to targeting diverse cellular processes inherent in PD and MS, with the emphasis placed on their neuroprotective and immune-regulating potentials in cellular and animal models. By reviewing the many similarities between PD and MS and NPs according to their functions, it becomes evident that some NPs studied for one disease are likely repurposable for the other. A review from this perspective can provide insights into the search for and utilization of NPs in treating the similar cellular processes common in major neurodegenerative diseases.

In silico studies of natural product-like caffeine derivatives as potential MAO-B inhibitors/AA2AR antagonists for the treatment of Parkinson's disease

Parkinson's disease is considered the second most frequent neurodegenerative disease. It is described by the loss of dopaminergic neurons in the mid-brain. For many decades, L-DOPA has been considered as the gold standard for treating Parkinson's disease motor symptoms, however, due to the decrease of efficacy, in the long run, there is an urgent need for novel antiparkinsonian drugs. Caffeine derivatives have been reported several times for their neuroprotective properties and dual blockade of monoamine oxidase (MAO) and adenosine A2A receptors (AA2AR). Natural products are currently attracting more focus due to structural diversity and safety in contrast to synthetic drugs. In the present work, computational studies were conducted on natural product-like caffeine derivatives to search for novel potent candidates acting as dual MAO-B inhibitors/AA2AR antagonists for Parkinson's disease. Our findings revealed two natural products among the top hits: CNP0202316 and CNP0365210 fulfill the requirements of drugs acting on the brain. The selected lead compounds were further studied using molecular dynamics simulation to assess their stability with MAO-B. Current findings might shift the interest towards natural-based compounds and could be exploited to further optimize caffeine derivatives into a successful dual-target-directed drug for managing and halting the neuronal damage in Parkinson's disease patients.

Assessment of caffeine neurotoxicity using novel biomarkers of neural function in SH-SY5Y cells - Is there a need for environmental concern?

Worldwide usage of caffeine results in its constant release into the aquatic environment and growing concerns related to associated risks. We assessed (neuro)toxicity of environmentally relevant concentrations of caffeine, using novel biomarkers of neural function in SH-SY5Y cells and markers of general toxicity also in HepG2 cells. The RQ-PCR analyses showed that caffeine disturbs the expression of genes encoding several key elements of neurotransmitter pathways, with the most prominent responses observed for serotonin receptor 3A, dopamine receptor D2, monoamine oxidase B and GABA-transaminase. Expression of genes encoding synaptotagmin 10 involved in exocytosis of neurotransmitters and ATPase Na⁺/K⁺ transporting subunit alpha 3 was also disturbed. Caffeine stimulated the activity of monoamine oxidase, while cytotoxicity and effects on mitochondrial membrane potential were not observed. Our study points out the new possible molecular targets of caffeine and suggests that the raising concerns related to its growing environmental presence are justified.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, "general chemicals," natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10-15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

Acute Effects of Caffeine Supplementation on Physical Performance, Physiological Responses, Perceived Exertion, and Technical-Tactical Skills in Combat Sports: A Systematic Review and Meta-Analysis

Although the effects of caffeine supplementation on combat sports performance have been extensively investigated, there is currently no consensus regarding its ergogenic benefits.This systematic review with meta-analysis aimed to summarize the studies investigating the effects of caffeine supplementation on different aspects of performance in combat sports and to quantitatively analyze the results of these studies to better understand the ergogenic effect of caffeine on combat sports outcomes. A systematic search for randomized placebo-controlled studies investigating the effects of caffeine supplementation on combat sports' performance was performed through Scopus, Pubmed, Web of Science and Cochrane Library databases up to 18 April 2022. Random-effects meta-analyses of standardized mean differences (Hedge's g) were performed to analyze the data. Twenty-six studies of good and excellent methodological quality (based on the Pedro scale) fulfilled the inclusion criteria. The meta-analysis results revealed caffeine has a small but evident effect size (ES) on handgrip strength (ES = 0.28; 95% CI: 0.04 to 0.52; p = 0.02), and total number of throws during the special judo fitness test (SJFT) (ES = 0.42; 95% CI: 0.06 to 0.78; p = 0.02). Regarding the physiological responses, caffeine increased blood lactate concentration ([La]) in anaerobic exercise (ES = 1.23; 95% CI: 0.29 to 2.18; p = 0.01) and simulated combat (ES = 0.91; 95% CI: 0.34 to 1.47; p = 0.002). For Heart Rate (HR), caffeine increased HR final (ES = 0.31; 95% CI: 0.11 to 0.52; p = 0.003), and HR 1min (ES = 0.20; 95% CI 0.004 to 0.40; p = 0.045). However, caffeine had no impact on the countermovement jump height, the SJFT index, the judogi strength-endurance test, the number and duration of offensive actions, HR at the end of the fight, and the rating of perceived exertion. Caffeine supplementation may be ergogenic for a range of combat sports aspects involving isometric strength, anaerobic power, reaction time, and anaerobic metabolism. However, supplementation effects might be ineffective under certain circumstances, indicating supplementation needs to take into account the performance metric in question prior to creating a dosing protocol.

Adenosine A2A receptor antagonists: from caffeine to selective non-xanthines

A long evolution of knowledge of the psychostimulant caffeine led in the 1960s to another purine natural product, adenosine and its A2A receptor. Adenosine is a short-lived autocrine/paracrine mediator that acts pharmacologically at four different adenosine receptors in a manner opposite to the pan-antagonist caffeine and serves as an endogenous allostatic regulator. Although detrimental in the developing brain, caffeine appears to be cerebroprotective in aging. Moderate caffeine consumption in adults, except in pregnancy, may also provide benefit in pain, diabetes, and kidney and liver disorders. Inhibition of A2A receptors is one of caffeine's principal effects and we now understand this interaction at the atomic level. The A2A receptor has become a prototypical example of utilizing high-resolution structures of GPCRs for the rational design of chemically diverse drug molecules. The previous focus on discovery of selective A2A receptor antagonists for neurodegenerative diseases has expanded to include immunotherapy for cancer, and clinical trials have ensued. LINKED ARTICLES: This article is part of a themed issue on Structure Guided Pharmacology of Membrane Proteins (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.14/issuetoc.

Beyond AOPs: A Mechanistic Evaluation of NAMs in DART Testing

New Approach Methodologies (NAMs) promise to offer a unique opportunity to enable human-relevant safety decisions to be made without the need for animal testing in the context of exposure-driven Next Generation Risk Assessment (NGRA). Protecting human health against the potential effects a chemical may have on embryo-foetal development and/or aspects of reproductive biology using NGRA is particularly challenging. These are not single endpoint or health effects and risk assessments have traditionally relied on data from Developmental and Reproductive Toxicity (DART) tests in animals. There are numerous Adverse Outcome Pathways (AOPs) that can lead to DART, which means defining and developing strict testing strategies for every AOP, to predict apical outcomes, is neither a tenable goal nor a necessity to ensure NAM-based safety assessments are fit-for-purpose. Instead, a pragmatic approach is needed that uses the available knowledge and data to ensure NAM-based exposure-led safety assessments are sufficiently protective. To this end, the mechanistic and biological coverage of existing NAMs for DART were assessed and gaps to be addressed were identified, allowing the development of an approach that relies on generating data relevant to the overall mechanisms involved in human reproduction and embryo-foetal development. Using the knowledge of cellular processes and signalling pathways underlying the key stages in reproduction and development, we have developed a broad outline of endpoints informative of DART. When the existing NAMs were compared against this outline to determine whether they provide comprehensive coverage when integrated in a framework, we found them to generally cover the reproductive and developmental processes underlying the traditionally evaluated apical endpoint studies. The application of this safety assessment framework is illustrated using an exposure-led case study.

Caffeine increases performance and leads to a cardioprotective effect during intense exercise in cyclists

The present study was designed to investigate the effects of different caffeine dietary strategies to compare the impact on athletic performance and cardiac autonomic response. The order of the supplementation was randomly assigned: placebo(4-day)-placebo(acute)/PP, placebo(4-day)-caffeine(acute)/PC and caffeine(4-day)-caffeine(acute)/CC. Fourteen male recreationally-trained cyclists ingested capsules containing either placebo or caffeine (6 mg kg-1) for 4 days. On day 5 (acute), capsules containing placebo or caffeine (6 mg kg-1) were ingested 60 min before completing a 16 km time-trial (simulated cycling). CC and PC showed improvements in time (CC vs PP, Δ - 39.3 s and PC vs PP, Δ - 43.4 s; P = 0.00; ƞ2 = 0.33) and in output power (CC vs PP, Δ 5.55 w and PC vs PP, Δ 6.17 w; P = 0.00; ƞ2 = 0.30). At the final of the time-trial, CC and PC exhibited greater parasympathetic modulation (vagal tone) when compared to the PP condition (P < 0.00; ƞ2 = 0.92). Our study provided evidence that acute caffeine intake (6 mg∙kg-1) increased performance (time-trial) and demonstrated a relevant cardioprotective effect, through increased vagal tone.

Design and synthesis of novel chalcone derivatives and evaluation of their inhibitory activities against acetylcholinesterase

According to the cholinergic hypothesis, an increase in the acetylcholine level in Alzheimer's disease patients relatively slows down the symptoms of the disease. The most commonly used drug, donepezil, is a cholinesterase inhibitor. In this study, 12 new chalcones (2a-l) were designed and synthesized. In biological activity studies, the acetylcholinesterase (AChE) and butyrylcholinesterase inhibitory potentials of all compounds were evaluated using the in vitro Ellman method. The biological evaluation showed that compounds 2d, 2f, 2j, and 2l displayed significant activity against AChE. The compounds 2d, 2f, 2j, and 2l displayed IC₅₀ values of 0.042, 0.024, 0.053, and 0.033 µM against AChE, respectively. The reference drug donepezil (IC₅₀  = 0.021 µM) also displayed significant inhibition of AChE. The inhibitory activities of these compounds for β-amyloid plaque aggregation were investigated. The enzyme kinetic study was performed to observe the effect of the most active compound 2f on the substrate-enzyme relationship, and a mixed-type inhibition of AchE was determined. Further, docking simulation also revealed that these compounds (2d, 2f, 2j, and 2l) interacted with the enzyme active site in a similar manner to donepezil. The most active derivative, compound 2f, interacted with the amino acids Trp286, Phe295, Tyr341, Trp86, and Glu202.

Selected natural and synthetic agents effective against Parkinson's disease with diverse mechanisms

Similar to other neurodegenerative diseases, Parkinson's disease (PD) has been extensively investigated with respect to its neuropathological background and possible treatment options. Since the symptomatic outcomes are generally related to dopamine deficiency, the current treatment strategies towards PD mainly employ dopaminergic agonists as well as the compounds acting on dopamine metabolism. These drugs do not provide disease modifying properties; therefore alternative drug discovery studies focus on targets involved in the progressive neurodegenerative character of PD. This study has aimed to present the pathophysiology of PD concomitant to the representation of drugs and promising molecules displaying activity against the validated and non-validated targets of PD.

Novel Facet of an Old Dietary Molecule? Direct Influence of Caffeine on Glucose and Biogenic Amine Handling by Human Adipocytes

Caffeine is a plant alkaloid present in food and beverages consumed worldwide. It has high lipid solubility with recognized actions in the central nervous system and in peripheral tissues, notably the adipose depots. However, the literature is scant regarding caffeine's influence on adipocyte functions other than lipolysis, such as glucose incorporation into lipids (lipogenesis) and amine oxidation. The objective of this study was to explore the direct effects of caffeine and of isobutylmethylxanthine (IBMX) on these adipocyte functions. Glucose transport into fat cells freshly isolated from mice, rats, or humans was monitored by determining [³H]-2-deoxyglucose (2-DG) uptake, while the incorporation of radiolabeled glucose into cell lipids was used as an index of lipogenic activity. Oxidation of benzylamine by primary amine oxidase (PrAO) was inhibited by increasing doses of caffeine in human adipose tissue preparations with an inhibition constant (Ki) in the millimolar range. Caffeine inhibited basal and insulin-stimulated glucose transport as well as lipogenesis in rodent adipose cells. The antilipogenic action of caffeine was also observed in adipocytes from mice genetically invalidated for PrAO activity, indicating that PrAO activity was not required for lipogenesis inhibition. These caffeine inhibitory properties were extended to human adipocytes: relative to basal 2-DG uptake, set at 1.0 ± 0.2 for 6 individuals, 0.1 mM caffeine tended to reduce uptake to 0.83 ± 0.08. Insulin increased uptake by 3.86 ± 1.11 fold when tested alone at 100 nM, and by 3.21 ± 0.80 when combined with caffeine. Our results reinforce the recommendation of caffeine's potential in the treatment or prevention of obesity complications.

Evaluation of the inhibition of monoamine oxidase A by bioactive coffee compounds protecting serotonin degradation

Monoamine oxidase A (MAO-A) is a major enzyme responsible for the deamination of neurotransmitters such as serotonin (5-HT) in the central nervous system. The decrease in 5-HT levels is accompanied by disorders at the affective and somatic levels, leading to depression and disorders of the satiety center. The aim of this study was to evaluate the degree of MAO-A inhibition by chlorogenic acids, as well as green, light-, and dark-roasted coffee extracts and bioactive compounds from beans of the species Coffea canephora and Coffea arabica. Data for analysis was obtained using isothermal titration calorimetry and molecular docking. The results showed that caffeine and ferulic acid, as well as green Robusta coffee, demonstrated the greatest inhibition of MAO-A activity, which may increase the bioavailability of serotonin. We believe that green coffee shows potential antidepressant activity by inhibiting MAO-A, and may be used for treating depression and potentially, type 2 diabetes.

Novel 1,3,4-thiadiazole compounds as potential MAO-A inhibitors - design, synthesis, biological evaluation and molecular modelling

Monoamine oxidases (MAOs) are important drug targets for the management of neurological disorders. Herein, a series of new 1,3,4-thiadiazole derivatives bearing various alkyl/arylamine moieties as MAO inhibitors were designed and synthesized. All of the compounds were more selective against hMAO-A than hMAO-B. The half maximal inhibitory concentration (IC₅₀) values of most of the compounds were lower than that of the common drug moclobemide (IC₅₀ = 4.664 μM) and compound 6b was proven to be the most active compound (IC₅₀ = 0.060 μM). Moreover, it was seen that compound 6b showed a similar inhibition profile to that of clorgyline (IC₅₀ = 0.048 μM). The inhibition profile was found to be reversible and competitive for compound 6b with MAO-A selectivity. Molecular modelling studies aided in the understanding of the interaction modes between compound 6b and MAO-A. Furthermore, this compound was predicted to have a good pharmacokinetic profile and high BBB penetration. Therefore, such compounds are of interest towards developing new MAO inhibitors.

Methylxanthines Inhibit Primary Amine Oxidase and Monoamine Oxidase Activities of Human Adipose Tissue

Background: Methylxanthines including caffeine and theobromine are widely consumed compounds and were recently shown to interact with bovine copper-containing amine oxidase. To the best of our knowledge, no direct demonstration of any interplay between these phytochemicals and human primary amine oxidase (PrAO) has been reported to date. We took advantage of the coexistence of PrAO and monoamine oxidase (MAO) activities in human subcutaneous adipose tissue (hScAT) to test the interaction between several methylxanthines and these enzymes, which are involved in many key pathophysiological processes. Methods: Benzylamine, methylamine, and tyramine were used as substrates for PrAO and MAO in homogenates of subcutaneous adipose depots obtained from overweight women undergoing plastic surgery. Methylxanthines were tested as substrates or inhibitors by fluorimetric determination of hydrogen peroxide, an end-product of amine oxidation. Results: Semicarbazide-sensitive PrAO activity was inhibited by theobromine, caffeine, and isobutylmethylxanthine (IBMX) while theophylline, paraxanthine, and 7-methylxanthine had little effect. Theobromine inhibited PrAO activity by 54% at 2.5 mM. Overall, the relationship between methylxanthine structure and the degree of inhibition was similar to that seen with bovine PrAO, although higher concentrations (mM) were required for inhibition. Theobromine also inhibited oxidation of tyramine by MAO, at the limits of its solubility in a DMSO vehicle. At doses higher than 12 % v/v, DMSO impaired MAO activity. MAO was also inhibited by millimolar doses of IBMX, caffeine and by other methylxanthines to a lesser extent. Conclusions: This preclinical study extrapolates previous findings with bovine PrAO to human tissues. Given that PrAO is a potential target for anti-inflammatory drugs, it indicates that alongside phosphodiesterase inhibition and adenosine receptor antagonism, PrAO and MAO inhibition could contribute to the health benefits of methylxanthines, especially their anti-inflammatory effects.

Screening for drugs to reduce zebrafish aggression identifies caffeine and sildenafil

Although aggression is a common symptom of psychiatric disorders the drugs available to treat it are non-specific and can have unwanted side effects. In this study we have used a behavioural platform in a phenotypic screen to identify drugs that can reduce zebrafish aggression without affecting locomotion. In a three tier screen of ninety-four drugs we discovered that caffeine and sildenafil can selectively reduce aggression. Caffeine also decreased attention and increased impulsivity in the 5-choice serial reaction time task whereas sildenafil showed the opposite effect. Imaging studies revealed that both caffeine and sildenafil are active in the zebrafish brain, with prominent activation of the thalamus and cerebellum evident. They also interact with 5-HT neurotransmitter signalling. In summary, we have demonstrated that juvenile zebrafish are a suitable model to screen for novel drugs to reduce aggression, with the potential to uncover the neural circuits and signalling pathways that mediate such behavioural effects.

Protective Effects of the Caffeine Against Neurodegenerative Diseases

Background:

Recent studies and increased interest of the scientific community helped to clarify the neurological health property of caffeine, one of the pharmacologically active substances most consumed in the world.

Methods:

This article is a review search to provide an overview on the current state of understanding neurobiochemical impact of caffeine, focusing on the ability of the drug to effectively counteract several neurodegenerative disorders such as Alzheimer’s, Parkinson’s, Huntington’s diseases, Multiple sclerosis and Amyotrophic lateral sclerosis.

Results:

Data collection shown in this review provide a significant therapeutic and prophylactic potentiality of caffeine which acts on human brain through several pathways because of its antioxidant activity combined with multiple molecular targets. However, the need to adjust the CF dosage to individuals, because some people are more sensitive to drugs than others, may constituted a limit to the CF effectiveness.

Conclusion:

What emerges from the complex of clinical and epidemiological studies is a significant CF potential impact against all neurological disorders. Although, further studies are needed to fully elucidate the several mechanisms of drug action which in part are still elusive.

Design, Synthesis and Evaluation of 8-Thiosubstituted 1,3,7- Trimethylxanthine Hydrazones with In-vitro Neuroprotective and MAO-B Inhibitory Activities

OBJECTIVE

The syntheses and biological activities of 8-thiosubstituted-1,3,7- trimethylxanthine derivatives bearing an aromatic hydrazide-hydrazone fragment in the side chain at C8 are described.

METHODS

The chemical structures of the synthesized compounds 6a-m were confirmed based on their MS, FTIR, 1H NMR and 13C NMR analyses.

RESULTS

The in vitro investigations of neuroprotective effects manifested on cellular (human neuroblastoma cell line SH-SY5Y) and sub-cellular (isolated rat brain synaptosomes) levels show that compounds 6g and 6i demonstrate statistically significant activity. The performed monoamine oxidase B (MAO-B) inhibition study in vitro show that compounds 6g and 6i possess a significant MAO-B inhibition activity close to L-deprenyl.

CONCLUSION

These results suggest that such compounds may be utilized for the development of new candidate MAO-B inhibitors for the treatment of Parkinson's disease.

Resveratrol Anti-Obesity Effects: Rapid Inhibition of Adipocyte Glucose Utilization

Studies in animal models of diabetes and obesity have shown that resveratrol mitigates complications of metabolic diseases, beyond those resulting from oxidative stress. Furthermore, results obtained with cultured preadipocytes have also revealed that prolonged resveratrol treatment impairs adipogenesis. Considering the role of adipocytes in the hypertrophy of fat stores, and keeping in mind that insulin is the main trigger of excessive energy storage during post-prandial periods, the present study aimed to investigate how short-term effects of resveratrol can limit glucose disposal in a gut-adipose tissue axis. We found that resveratrol exhibits a more potent inhibitory capacity towards α-glucosidase than pancreatic lipase activity. Resveratrol also rapidly blunts glucose transport in mature fat cells by counteracting the effect of insulin and insulin-like lipogenic agents. Within two hours, resveratrol also inhibited the incorporation of glucose into lipids of adipocytes, which was unaffected by membrane cholesterol depletion. Moreover, the comparison between adipocytes with invalidated semicarbazide-sensitive amine oxidase activity and their control, or between resveratrol and several inhibitors, did not indicate that the recently described interaction of resveratrol with amine oxidases was involved in its antilipogenic effect. Caffeine and piceatannol, previously said to interact with glucose carriers, also inhibit lipogenesis in adipocytes, whereas other antioxidant phytochemicals do not reproduce such an antilipogenic effect. This study highlights the diverse first steps by which resveratrol impairs excessive fat accumulation, indicating that this natural molecule and its derivatives deserve further studies to develop their potential anti-obesity properties.

Ligand fishing of anti-neurodegenerative components from Lonicera japonica using magnetic nanoparticles immobilised with monoamine oxidase B

In this work, monoamine oxidase B was immobilised onto magnetic nanoparticles to prepare a new type of affinity solid-phase extraction adsorbent, which was used to extract the possible anti-neurodegenerative components from the Lonicera japonica flower extracts. Coupled with high-performance liquid chromatography with mass spectrometry, two monoamine oxidase B ligands were fished-out and identified as isochlorogenic acid A and isochlorogenic acid C, which were found to be inhibitors of the enzyme for the first time, with similar half maximal inhibitory concentration values of 29.05 ± 0.49 and 29.77 ± 1.03 μM, respectively. Furthermore, equilibrium-dialysis dissociation assay of enzyme-inhibitor complex showed that both compounds have reversible binding patterns to monoamine oxidase B, and kinetic analysis demonstrated that they were mixed-type inhibitors for monoamine oxidase B, with K_i and K_is values of 9.55 and 37.24 μM for isochlorogenic acid A, 9.53 and 35.50 μM for isochlorogenic acid C, respectively. The results indicated that isochlorogenic acid A and isochlorogenic acid C were the major active components responsible for the anti-degenerative activity of the flowers of L. japonica, while magnetic nanoparticles immobilised monoamine oxidase B could serve as an efficient solid-phase extraction adsorbent to specifically extract monoamine oxidase B inhibitors from complex herbal extracts.

Discovery of monoamine oxidase inhibitors by medicinal chemistry approaches

Neuropsychiatric disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD) and depression, have seriously inconvenienced the lives of patients. Growing evidence indicates that these diseases are closely related to the monoamine oxidase (MAO) enzyme, making it an attractive target for the exploitation of potent MAO inhibitors (MAOIs) with high selectivity and low side effects. Although various MAOIs have been discovered, the discovery of an ideal MAOI is not an easy task. In this review, we discuss the currently available rational design strategies for obtaining ideal MAOIs, including ligand-based and receptor-based design strategies, and these strategies were further illustrated with the aid of specific examples from the recent literature. To better understanding the biological activity of MAO, we also highlight the binding modes of typical inhibitors against MAO. Besides, advanced strategies for finding upcoming potent MAOIs were prospected.

Absolute configuration and biological profile of pyrazoline enantiomers as MAO inhibitory activity

A new racemic pyrazoline derivative was synthesized and resolved to its enantiomers using analytic and semipreparative high-pressure liquid chromatography. The absolute configuration of both fractions was established using vibrational circular dichroism. The in vitro monoamine oxidase (MAO) inhibitory profiles were evaluated for the racemate and both enantiomers separately for the two isoforms of the enzyme. The racemic compound and both enantiomers were found to inhibit hMAO-A selectively and competitively. In particular, the R enantiomer was detected as an exceptionally potent and a selective MAO-A inhibitor (K_i  = 0.85 × 10^-3  ± 0.05 × 10^-3  μM and SI: 2.35 × 10^-5 ), whereas S was determined as poorer compound than R in terms of K_i and SI (0.184 ± 0.007 and 0.001). The selectivity of the enantiomers was explained by molecular modeling docking studies based on the PDB enzymatic models of MAO isoforms.

3D-QSAR and in-silico Studies of Natural Products and Related Derivatives as Monoamine Oxidase Inhibitors

BACKGROUND

The computational development of human monoamine oxidase (MAO) inhibitors led to advancement in drug design and the treatment of many neurodegenerative diseases and neuropsychiatric disorders. The computational development of human monoamine oxidase (MAO) inhibitors led to advancement in drug design and the treatment of many neurodegenerative diseases and neuropsychiatric disorders. Different natural heterocyclic structures are reported to display selective MAO inhibitory activity by preclinical and in-silico modeling.

OBJECTIVE

Currently, the major interest is devoted to the study of natural based therapeutic agents from the different categories. Therefore, we presenting the review to critically discuss and outline the recent advances in our knowledge on the importance of natural and natural based ligand-MAO insilico methods for novel MAO inhibitors.

DISCUSSION

Several natural and related synthetic heterocyclic compounds such as coumarins, β- carboline, piperine, naphthoquinone, morpholine, caffeine, amphetamine moreover flavonoids, chalcones, xanthones, curcumin are discussed for their MAO inhibitory profile along with molecular docking and quantitative structure-activity relationship studies.

CONCLUSION

It is clear that, by this computational drug design approach, more particular, reversible and potent compounds can be proposed as MAO inhibitors by exact changes on the fundamental framework.

Imidazole bearing chalcones as a new class of monoamine oxidase inhibitors

In the present study, series of eleven (2E)-1-[4-(1H-imidazol-1-yl)substituted phenyl]-3-phenylprop-2-en-1-one (IM1-IM11) derivatives were synthesized and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The results indicate that (2E)-3-[4-(dimethylamino) phenyl]-1-[4-(1H-imidazol-1-yl) phenyl] prop-2-en-1-one (IM5) is a nonselective and reversible competitive inhibitor of MAO-A and MAO-B with IC₅₀ values of 0.30 ± 0.010 and 0.40 ± 0.017 μM, respectively ; those of (2E)-1-[4-(1H-imidazol-1-yl) phenyl]-3-(4-methylphenyl) prop-2-en-1-one (IM4) were 1.06 ± 0.090 and 0.32 ± 0.021 μM, respectively. Kinetic studies document that both IM5 and IM4 are competitive inhibitors of MAO-A and MAO-B with Ki value of 0.11 ± 0.0085 and 0.085 ± 0.0064 μM, respectively. Molecular docking studies of lead compounds further explained the binding modes in the inhibitor binding cavity of both MAO-A and MAO-B.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

Nutritional habits, risk, and progression of Parkinson disease

Parkinson disease (PD) is a multifactorial disease, where a genetic predisposition combines with putative environmental risk factors. Mounting evidence suggests that the initial PD pathological manifestations may be located in the gut to subsequently affect brain areas. Moreover, several lines of research demonstrated that there are bidirectional connections between the central nervous system and the gut, the "gut-brain axis" that influences both brain and gastrointestinal function. This opens a potential therapeutic window suggesting that specific dietary strategies may interact with the disease process and influence the risk of PD or modify its course. Dietary components can also theoretically modulate the chronic activation of the inflammatory response that is associated with aging, the strongest risk factor for PD, that has been suggested to hasten the underlying neurodegenerative process in PD. Here, we reviewed the evidence supporting an association between certain dietary compound and either the risk or progression of PD and have provided an overview of the possible pathomechanisms linking nutrition and neurodegeneration. The results of our review would not support a clear role for any dietary components in reducing the risk or progression of PD. However, the evidence favouring a connection between gut abnormalities, inflammation, and neurodegeneration in PD have become too compelling to be ignored, so that further research, also in the field of nutritional genomics, is highly warranted.

Neuroprotective and Therapeutic Effect of Caffeine on the Rat Model of Parkinson's Disease Induced by Rotenone

The present study aimed to investigate the protective and therapeutic effects of caffeine on rotenone-induced rat model of Parkinson's disease (PD). Rats were divided into control, PD model induced by rotenone (1.5 mg/kg intraperitoneally (i.p.) for 45 days), protected group injected with caffeine (30 mg/kg, i.p.) and rotenone for 45 days (during the development of PD model), and treated group injected with caffeine (30 mg/kg, i.p.) for 45 days after induction of PD model. The data revealed a state of oxidative and nitrosative stress in the midbrain and the striatum of animal model of PD as indicated from the increased lipid peroxidation and nitric oxide levels and the decreased reduced glutathione level and activities of glutathione-S-transferase and superoxide dismutase. Rotenone induced a decrease in acetylcholinesterase and Na⁺/K⁺-ATPase activities and an increase in tumor necrosis factor-α level in the midbrain and the striatum. Protection and treatment with caffeine ameliorated the oxidative stress and the changes in acetylcholinesterase and Na⁺/K⁺-ATPase activities induced by rotenone in the midbrain and the striatum. This was associated with improvement in the histopathological changes induced in the two areas of PD model. Caffeine protection and treatment restored the depletion of midbrain and striatal dopamine induced by rotenone and prevented decline in motor activities (assessed by open field test) and muscular strength (assessed by traction and hanging tests) and improved norepinephrine level in the two areas. The present study showed that caffeine offered a significant neuroprotection and treatment against neurochemical, histopathological, and behavioral changes in a rotenone-induced rat model of PD.

Inhibition of Human Monoamine Oxidase: Biological and Molecular Modeling Studies on Selected Natural Flavonoids

Naturally occurring flavonoids display a plethora of different biological activities, but emerging evidence suggests that this class of compounds may also act as antidepressant agents endowed with multiple mechanisms of action in the central nervous system, increasing central neurotransmission, limiting the reabsorption of bioamines by synaptosomes, and modulating the neuroendocrine and GABA_A systems. Due to their presence in foods, food-derived products, and nutraceuticals, we established their role and structure-activity relationships as reversible and competitive human monoamine oxidase (MAO) inhibitors. In addition, molecular modeling studies, which evaluated their modes of MAO inhibition, are presented. These findings could provide pivotal implications in the quest of novel drug-like compounds and for the establishment of harmful drug-dietary supplement interactions commonly reported in the therapy with antidepressant agents.

Monoamine Oxidase Inhibitory Activity: Methyl- versus Chlorochalcone Derivatives

Numerous studies have shown that chalcones are promising scaffolds for the development of new monoamine oxidase-B (MAO-B) inhibitors. As a continuation of our ongoing research into the development of reversible human MAO-B (hMAO-B) inhibitors, two series of twenty chalcones containing electron-donating and electron-withdrawing substituents were synthesized. All compounds were found to be competitive, selective, and reversible inhibitors of hMAO-B except (2E)-1-(4-methylphenyl)-3-(4-nitrophenyl)prop-2-en-1-one (P7) and (2E)-1-(4-chlorophenyl)-3-(4-nitrophenyl)prop-2-en-1-one (P17), which were found to be selective inhibitors of hMAO-A. The most potent hMAO-B inhibitor, (2E)-1-(4-chlorophenyl)-3-(4-ethylphenyl)prop-2-en-1-one (P16), showed a K_i value of 0.11±0.01 μm. Molecular docking simulations were carried out to identify the hypothetical binding mode for the most potent compounds in the active sites of hMAO-A and B. The ability of the compounds to cross the blood-brain barrier was assessed by parallel artificial membrane permeability assay (PAMPA). Additionally, the most potent hMAO-B inhibitor P16 showed no toxicity in cultured hepatic cells at concentrations of 5 and 25 μm.

Caffeine Induces a Stimulant Effect and Increases Dopamine Release in the Nucleus Accumbens Shell Through the Pulmonary Inhalation Route of Administration in Rats

Oral, intraperitoneal, or intravenous have been the common routes of administration used to study the behavioral and neurochemical pharmacology of caffeine, one of the most widely used psychoactive substances worldwide. We have reported that caffeine is an active adulterant frequently found in coca-paste (CP)-seized samples, a highly addictive form of smokable cocaine. The role of caffeine in the psychostimulant and neurochemical effects induced by CP remains under study. No preclinical animal studies have been performed so far to characterize the effects of caffeine when it is administered through the pulmonary inhalation route. Caffeine (10, 25, and 50 mg) was volatilized and rats were exposed to one inhalation session of its vapor. The stimulant effect was automatically recorded and plasmatic levels of caffeine were measured. Caffeine capability (50 mg) to increase extracellular dopamine (DA) levels in nucleus accumbens shell was also studied by in vivo microdialysis in non-anesthetized animals. A dose-dependent stimulant effect induced by volatilized caffeine was observed and this effect was directly related with caffeine plasmatic levels. A significant increase in the extracellular DA was achieved after 50 mg of volatilized caffeine exposure. This is the first report showing pharmacological acute effects of caffeine through the pulmonary inhalation route of administration and suggests that this could be a condition under which caffeine can elevate its weak reinforcing effect and even enhance the psychostimulant effect and abuse liability of smokable adulterated psychostimulant drugs.

Structure-Bioactivity Relationships of Methylxanthines: Trying to Make Sense of All the Promises and the Drawbacks

Methylxanthines are a group of phytochemicals derived from the purine base xanthine and obtained from plant secondary metabolism. They are unobtrusively included in daily diet in common products as coffee, tea, energetic drinks, or chocolate. Caffeine is by far the most studied methylxanthine either in animal or epidemiologic studies. Theophylline and theobromine are other relevant methylxanthines also commonly available in the aforementioned sources. There are many disseminated myths about methylxanthines but there is increased scientific knowledge to discuss all the controversy and promise shown by these intriguing phytochemicals. In fact, many beneficial physiologic outcomes have been suggested for methylxanthines in areas as important and diverse as neurodegenerative and respiratory diseases, diabetes or cancer. However, there have always been toxicity concerns with methylxanthine (over)consumption and pharmacologic applications. Herein, we explore the structure-bioactivity relationships to bring light those enumerated effects. The potential shown by methylxanthines in such a wide range of conditions should substantiate many other scientific endeavors that may highlight their adequacy as adjuvant therapy agents and may contribute to the advent of functional foods. Newly designed targeted molecules based on methylxanthine structure may originate more specific and effective outcomes.

Identification of Indole-Based Chalcones: Discovery of a Potent, Selective, and Reversible Class of MAO-B Inhibitors

A series of 11 indole-based chalcones (IC1-11) with various electron donating and withdrawing groups at the para position of the phenyl ring B were synthesized. All the compounds were tested for their human monoamine oxidase (hMAO)-A and hMAO-B inhibitory potencies. Most of the synthesized candidates proved to be potent and selective inhibitors of MAO-B rather than MAO-A, with a reversible and competitive mode. Among them, compound IC9 was found to be a potent inhibitor of hMAO-B with Ki  = 0.01 ± 0.005 μM and a selectivity index of 120. It was found to be better than the standard drug, selegiline (hMAO-B with Ki  = 0.20 ± 0.020 μM) with a selectivity index of 30.55. PAMPA assays were carried out for all the compounds in order to evaluate the capacity of the compounds to cross the blood-brain barrier. Moreover, the most potent MAO-B inhibitor, IC9, was nontoxic at 5 and 25 μM, with 95.20 and 69.17% viable cells, respectively. The lead compound IC9 has an antioxidant property of 1.18 Trolox equivalents by ABTS assay. Molecular modeling studies were performed against hMAO-B to observe binding site interactions of the lead compound.

Synthesis, Biochemistry, and Computational Studies of Brominated Thienyl Chalcones: A New Class of Reversible MAO-B Inhibitors

A series of (2E)-1-(5-bromothiophen-2-yl)-3-(para-substituted phenyl)prop-2-en-1-ones (TB1-TB11) was synthesized and tested for inhibitory activity toward human monoamine oxidase (hMAO). All compounds were found to be competitive, selective, and reversible toward hMAO-B except (2E)-1-(5-bromothiophen-2-yl)-3-(4-nitrophenyl)prop-2-en-1-one (TB7) and (2E)-1-(5-bromothiophen-2-yl)-3-(4-chlorophenyl)prop-2-en-1-one (TB8), which were selective inhibitors of hMAO-A. The most potent compound, (2E)-1-(5-bromothiophen-2-yl)-3-[4-(dimethylamino)phenyl]prop-2-en-1-one (TB5), showed the best inhibitory activity and higher selectivity toward hMAO-B, with Ki and SI values of 0.11±0.01 μm and 13.18, respectively. PAMPA assays for all compounds were carried out in order to evaluate the capacity of the compounds to cross the blood-brain barrier. Moreover, the most potent MAO-B inhibitor, TB5, was found to be nontoxic at 5 and 25 μm, with 95.75 and 84.59 % viability among cells, respectively. Molecular docking simulations were carried out to understand the crucial interactions responsible for selectivity and potency.

Caffeine and cardiovascular diseases: critical review of current research

Caffeine is a most widely consumed physiological stimulant worldwide, which is consumed via natural sources, such as coffee and tea, and now marketed sources such as energy drinks and other dietary supplements. This wide use has led to concerns regarding the safety of caffeine and its proposed beneficial role in alertness, performance and energy expenditure and side effects in the cardiovascular system. The question remains "Which dose is safe?", as the population does not appear to adhere to the strict guidelines listed on caffeine consumption. Studies in humans and animal models yield controversial results, which can be explained by population, type and dose of caffeine and low statistical power. This review will focus on comprehensive and critical review of the current literature and provide an avenue for further study.

Evaluation of Natural and Synthetic 1,4-naphthoquinones as Inhibitors of Monoamine Oxidase

Previous reports have documented that 1,4-naphthoquinones act as inhibitors of the monoamine oxidase (MAO) enzymes. In particular, fractionation of the extracts of cured tobacco leafs has led to the characterization of 2,3,6-trimethyl-1,4-naphthoquinone, a non-selective MAO inhibitor. To derive structure-activity relationships for MAO inhibition by the 1,4-naphthoquinone class of compounds, this study investigates the human MAO inhibitory activities of fourteen structurally diverse 1,4-naphthoquinones of natural and synthetic origin. Of these, 5,8-dihydroxy-1,4-naphthoquinone was found to be the most potent inhibitor with an IC50 value of 0.860 μm for the inhibition of MAO-B. A related compound, shikonin, inhibits both the MAO-A and MAO-B isoforms with IC50 values of 1.50 and 1.01 μm, respectively. It is further shown that MAO-A and MAO-B inhibition by these compounds is reversible by dialysis. In this respect, kinetic analysis suggests that the modes of MAO inhibition are competitive. This study contributes to the discovery of novel MAO inhibitors, which may be useful in the treatment for disorders such as Parkinson's disease, depressive illness, congestive heart failure and cancer.

2-acetylphenol analogs as potent reversible monoamine oxidase inhibitors

Based on a previous report that substituted 2-acetylphenols may be promising leads for the design of novel monoamine oxidase (MAO) inhibitors, a series of C5-substituted 2-acetylphenol analogs (15) and related compounds (two) were synthesized and evaluated as inhibitors of human MAO-A and MAO-B. Generally, the study compounds exhibited inhibitory activities against both MAO-A and MAO-B, with selectivity for the B isoform. Among the compounds evaluated, seven compounds exhibited IC₅₀ values <0.01 µM for MAO-B inhibition, with the most selective compound being 17,000-fold selective for MAO-B over the MAO-A isoform. Analyses of the structure–activity relationships for MAO inhibition show that substitution on the C5 position of the 2-acetylphenol moiety is a requirement for MAO-B inhibition, and the benzyloxy substituent is particularly favorable in this regard. This study concludes that C5-substituted 2-acetylphenol analogs are potent and selective MAO-B inhibitors, appropriate for the design of therapies for neurodegenerative disorders such as Parkinson’s disease.