catechol-O-methyltransferase Inhibitor Research Articles

Dietary Magnesium Insufficiency Induces Salt-Sensitive Hypertension in Mice Associated With Reduced Kidney Catechol-O-Methyl Transferase Activity.

[Figure: see text].

Nordihydroguaiaretic Acid as a Novel Substrate and Inhibitor of Catechol O-Methyltransferase Modulates 4-Hydroxyestradiol-Induced Cyto- and Genotoxicity in MCF-7 Cells.

Nordihydroguaiaretic acid (NDGA) is a major lignan metabolite found in Larrea spp., which are widely used in South America to treat various diseases. In breast tissue, estradiol is metabolized to the catechol estrogens such as 4-hydroxyestradiol (4-OHE2), which have been proposed to be cancer initiators potentially involved in mammary carcinogenesis. Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of catechol estrogens to their less toxic methoxy derivatives, such as 4-O-methylestradiol (4-MeOE2). The present study investigated the novel biological activities of NDGA in relation to COMT and the effects of COMT inhibition by NDGA on 4-OHE2-induced cyto- and genotoxicity in MCF-7 human breast cancer cells. Two methoxylated metabolites of NDGA, 3-O-methylNDGA (3-MNDGA) and 4-O-methyl NDGA (4-MNDGA), were identified in the reaction mixture containing human recombinant COMT, NDGA, and cofactors. Km values for the COMT-catalyzed metabolism of NDGA were 2.6 µM and 2.2 µM for 3-MNDGA and 4-MNDGA, respectively. The COMT-catalyzed methylation of 4-OHE2 was inhibited by NDGA at an IC50 of 22.4 µM in a mixed-type mode of inhibition by double reciprocal plot analysis. Molecular docking studies predicted that NDGA would adopt a stable conformation at the COMT active site, mainly owing to the hydrogen bond network. NDGA is likely both a substrate for and an inhibitor of COMT. Comet and apurinic/apyrimidinic site quantitation assays, cell death, and apoptosis in MCF-7 cells showed that NDGA decreased COMT-mediated formation of 4-MeOE2 and increased 4-OHE2-induced DNA damage and cytotoxicity. Thus, NDGA has the potential to reduce COMT activity in mammary tissues and prevent the inactivation of mutagenic estradiol metabolites, thereby increasing catechol estrogen-induced genotoxicities.

New therapeutic agents marketed in 2020: Part 2

New therapeutic agents marketed in 2020: Part 2

Dopaminergic modulation of regional cerebral blood flow: An arterial spin labelling study of genetic and pharmacological manipulation of COMT activity

Dopamine has direct and complex vasoactive effects on cerebral circulation. Catechol-O-methyltransferase (COMT) regulates cortical dopamine, and its activity can be influenced both genetically and pharmacologically. COMT activity influences the functional connectivity of the PFC at rest, as well as its activity during task performance, determined using blood oxygen level-dependent (BOLD) fMRI. However, its effects on cerebral perfusion have been relatively unexplored. Here, 76 healthy males, homozygous for the functional COMT Val158Met polymorphism, were administered either the COMT inhibitor tolcapone or placebo in a double-blind, randomised design. We then assessed regional cerebral blood flow at rest using pulsed arterial spin labelling. Perfusion was affected by both genotype and drug. COMT genotype affected frontal regions (Val158 > Met158), whilst tolcapone influenced parietal and temporal regions (placebo > tolcapone). There was no genotype by drug interaction. Our data demonstrate that lower COMT activity is associated with lower cerebral blood flow, although the regions affected differ between those affected by genotype compared with those altered by acute pharmacological inhibition. The results extend the evidence for dopaminergic modulation of cerebral blood flow. Our findings also highlight the importance of considering vascular effects in functional neuroimaging studies, and of exercising caution in ascribing group differences in BOLD signal solely to altered neuronal activity if information about regional perfusion is not available.

Practical aspects of prescribing antiparkinsonian drugs. The place of amantadines in the management of Parkinson’s disease

Treatment of Parkinson’s disease (PD) includes the administration of dopaminergic and occasionally non-dopaminergic drugs, in mono- or in combination therapy. One of the key drug used to treat Parkinson’s disease is levodopa considered a gold standard. In addition levodopa can also be used as a challenge test to confirm the accuracy of diagnosis of PD known as the “Levodopa challenge test”. However many non levodopa class of drugs are also used and consist of dopamine agonists (ADRs), MAO-B and COMT inhibitors, as well as drugs working on glutamate such as a group of drug with NMDA receptor inhibitor activity (amantadines). The successful treatment of PD therefore depends on the correct choice of drugs to initiate treatment and sustainance of such therapy. The main parameters for personolised treatment include the patient’s age, severity and pattern of motor deficit, the state of cognitive function and lifestyle. Levodopa, although the most effective, is almost invariably associated with motor fluctuations and dyskinesias. Before prescribing levodopa, in addition to MAO-B inhibitors and ADRs, amantadines can be used as a monotherapy. Once replacement of therapy is required, then it is necessary to use a coefficient to calculate an equivalent dose of levodopa known as the levodopa equivalent dose. Progression of PD is inevitable inspite of adequate symptomatic therapy and at the advanced stage of PD approaches for the management of motor complications of levodopa need to be considered. For motor fluctuations these strategies require a change in the dosage regimen of levodopa (daily dose and frequency of intake), as well as the addition of an adjunct drug – ADRs, MAO-B inhibitor or COMT inhibitor. When dyskinesias arise, the management depends on correct identification of the type of dyskiensias. The commonest type of dyskinesia is peak dose dyskinesias related to peak plasma levodopa levels after intake. Amantadine provides a quick and long-lasting antidyskinetic effect which has been confirmed in open label as well as double-blind placebo-controlled studies. Compared to аmantadine chloride, amantadine sulfate has more stable pharmacokinetic parameters and a better safety profile. In addition, parenteral administration of amantadine sulfate can be utilized for severely ill patients with akinetic crisis in PD. Amantadine also has a broad spectrum effect and these may include improvement of fatigue and apathy. Some data also suggest that the use of amantadine in patients may increase life expectancy, improve survival and reduce the risk of dementia.

Discovery and characterization of naturally occurring potent inhibitors of catechol-O-methyltransferase from herbal medicines.

Human catechol-O-methyltransferase (hCOMT) is considered a therapeutic target due to its crucial roles in the metabolic inactivation of endogenous neurotransmitters and xenobiotic drugs. There are nevertheless few safe and effective COMT inhibitors and there lacks a diversity in structure. To discover novel safe and effective hCOMT inhibitors from herbal products, in this study, 53 herbal products were collected and their inhibitory effects against hCOMT were investigated. Among them, Scutellariae radix (SR) displayed the most potent inhibitory effect on hCOMT with an IC50 value of 0.75 μg mL−1. To further determine specific chemicals as COMT inhibitors, an affinity ultrafiltration coupled with liquid chromatography-mass spectrometry method was developed and successfully applied to identify COMT inhibitors from SR extract. The results demonstrated that scutellarein 2, baicalein 9 and oroxylin A 12 were potent COMT inhibitors, showing a high binding index (>3) and very low IC50 values (32.9 ± 3.43 nM, 37.3 ± 4.32 nM and 18.3 ± 2.96 nM). The results of inhibition kinetics assays and docking simulations showed that compounds 2, 9 and 12 were potent competitive inhibitors against COMT-mediated 3-BTD methylation, and they could stably bind to the active site of COMT. These findings suggested that affinity ultrafiltration allows a rapid identification of natural COMT inhibitors from a complex plant extract matrix. Furthermore, scutellarein 2, baicalein 9 and oroxylin A 12 are potent inhibitors of hCOMT in SR, which could be used as promising lead compounds to develop more efficacious non-nitrocatechol COMT inhibitors for biomedical applications.

Inhibition of catechol-O-methyltransferase by natural pentacyclic triterpenes: structure–activity relationships and kinetic mechanism

Inhibitors of COMT are clinically used for the treatment of Parkinson’s disease. Here, we report the first natural pentacyclic triterpenoid-type COMT inhibitors and their structure-activity relationships and inhibition mechanism. The most potent compounds were found to be oleanic acid, betulinic acid and celastrol with IC50 values of 3.89–5.07 μM, that acted as mixed (uncompetitive plus non-competitive) inhibitors of COMT, representing a new skeleton of COMT inhibitor. Molecular docking suggested that they can specifically recognise and bind with the unique hydrophobic residues surrounding the catechol pocket. Furthermore, oleanic acid and betulinic acid proved to be less disruptive of mitochondrial membrane potential (MMP) compared to tolcapone, thus reducing the risk of liver toxicity. These findings could be used to produce an ideal lead compound and to guide synthetic efforts in generating related derivatives for further preclinical testing.

Tissue and interspecies comparison of catechol-O-methyltransferase mediated catalysis of 6-O-methylation of esculetin to scopoletin and its inhibition by entacapone and tolcapone

Catechol-O-methyltransferase (COMT) methylates both endogenous and exogenous catechol compounds to inactive and safe metabolites. We first optimised conditions for a convenient and sensitive continuous fluorescence-based 6-O-methylation assay of esculetin, which we used for investigating the COMT activity in human, mouse, rat, dog, rabbit, and sheep liver cytosols and microsomes and in ten different rat tissues. Furthermore, we compared the inhibition potencies and mechanisms of two clinically used COMT inhibitors, entacapone and tolcapone, in these species. In most tissues, the COMT activity was at least three times higher in cytosol than in microsomes. In the rat, the highest COMT activity was found in the liver, followed by kidney, ileum, thymus, spleen, lung, pancreas, heart, brain, and finally, skeletal muscle. Entacapone and tolcapone were characterised as highly potent mixed type tight-binding inhibitors. The competitive inhibition type dominated over the uncompetitive inhibition with entacapone, whereas uncompetitive inhibition dominated with tolcapone. Rats, dogs, pigs, and sheep are high COMT activity species, in contrast to humans, mice, and rabbits; COMT activity is highest in the liver. Both entacapone and tolcapone are potent COMT inhibitors, but their inhibition mechanisms differ.

Pharmacology and Evidence-Based Strategies for Current and Emerging Treatments for OFF Periods in Parkinson Disease.

​​​​​​​​ Parkinson disease (PD) is a progressive neurodegenerative disease characterized by motor symptoms such as rigidity, resting tremor, and slowed movement in addition to nonmotor symptoms. As the disease advances and a patient's response duration to a levodopa dose is shortened, OFF episodes become more prevalent, negatively impacting their quality of life. Clinicians may employ a variety of therapeutic strategies to reduce OFF time, such as altering the levodopa dose or initiating adjuvant therapy. Medications to treat daily OFF time include dopamine agonists, MAO-B inhibitors, COMT inhibitors, amantadine ER, and adenosine A2A antagonists; as-needed rescue therapies include subcutaneous apomorphine, apomorphine sublingual film, and orally inhaled levodopa; and, when necessary, advanced therapies such as carbidopa/levodopa enteral suspension or DBS may be indicated.

Opicapone (Ongentys): A New COMT Inhibitor for the Treatment of Parkinson's Disease.

To describe the safety and efficacy of opicapone, a newly Food and Drug Administration-approved catechol-O-methyltransferase (COMT) inhibitor, as an adjunctive treatment to levodopa/carbidopa in patients with Parkinson's disease (PD) experiencing off episodes. A literature search through PubMed and International Pharmaceutical Abstracts (January 2000 to October 2020) was conducted using the following search terms: Ongentys, opicapone, COMT inhibitor, Parkinson's disease, and Parkinson's. Articles selected included those describing preclinical and clinical studies examining the pharmacokinetics, efficacy, and/or safety of opicapone. In preclinical trials, opicapone demonstrated marked S-COMT inhibition, despite its short half-life, while maintaining an acceptable safety and efficacy profile. Results from phase 3 clinical trials further supported the safety and efficacy of opicapone as an adjunct to levodopa. In addition, opicapone, at a dose of 50 mg once daily, was shown to be superior to placebo and noninferior to entacapone in reducing time spent in the off state. Adverse effects commonly reported with opicapone include dyskinesias, constipation, hypotension/syncope, increased blood creatine kinase, and decreased weight. Additional medications, such as COMT inhibitors, become necessary adjunctive treatments as the disease progresses. Compared to other COMT inhibitors currently on the US market, opicapone offers the advantage of once-daily dosing. Opicapone is a safe and effective COMT inhibitor shown to reduce off episodes in patients with PD.

The Past, Present, and Future of Parkinson's Disease Treatment

Parkinson’s Disease was first introduced by James Parkinson in 1817. Since then, major strides have been made in the development of its treatment. Early treatments were dominated by traditional and complementary therapies, which were largely serendipitous and observation-based. Especially, the use of anticholinergics by Jean-Martin Charcot and his student Ordenstein prevailed in the late 20th century. Current drug-based therapies manifest in the form of levodopa accompanied by dopamine agonist, COMT inhibitor, or MAO-B inhibitor, for the purpose of reducing the levodopa-induced symptom fluctuation. In terms of surgical treatment, while ablative surgeries in the brain have been abandoned due to high mortality rate in the late 1900s, Deep Brain Stimulation in the subthalamic nucleus or internal globus pallidus has mostly replaced ablative surgeries since its introduction in 1987. Current research topics include non-dopaminergic agents for motor fluctuation reduction, transplantation of dopaminergic neurons, gene therapies using viral vectors, reduction of alpha-synuclein neurotoxicity, and neuroprotective therapies. Especially, due to the fact that the etiology of the disease is yet to be elucidated, neuroprotective therapies aimed at slowing or stopping disease progression are of particular interest. It is suggested that future research should aim towards clarifying the cause of the disease, for the development of a treatment that can permanently halt or reverse Parkinson’s Disease-related neurodegeneration.

Opicapone Efficacy and Tolerability in Parkinson's Disease Patients Reporting Insufficient Benefit/Failure of Entacapone.

BackgroundOpicapone, a recently introduced catechol‐o‐methyl transferase (COMT) inhibitor has the advantage of being administered once daily, and has pharmacokinetic data to indicate it offers a greater degree of COMT inhibition than entacapone. Although trial data indicate it is non‐inferior to entacapone, there are no data to indicate whether it offers any clinical advantages.MethodsIn this audit, we present data from 57 individuals prescribed opicapone at the National Hospital for Neurology and Neurosurgery, Queen Square who had either not tolerated or reported insufficient benefit following previous prescription of entacapone.ResultsA total of 20 of 57 patients switched directly from entacapone to opicapone (“entacapone switchers”) whereas 37 of 57 patients had previously discontinued entacapone because of lack of benefit or adverse events (“entacapone failures”). A total of 21 of 57 (37%) patients stopped opicapone prior to 6 months. A total of 7 of 20 (35%) “entacapone switchers” experienced adverse events with opicapone of which 5 stopped the drug prior to the 6 month evaluation of efficacy. A total of 23 of 37 (62%) “entacapone failures” reported adverse events of which 16 stopped the drug. Among 36 of 57 (63%) patients who continued to use opicapone at 6 months, there was an improvement in OFF time of ~2 hours per day as measured by interview.ConclusionsWe conclude that opicapone can be an effective additional treatment for wearing off in Parkinson's disease (PD) in a subgroup of patients. The use of opicapone in our cohort with prior entacapone exposure, however, was associated with higher rates of adverse effects and treatment discontinuation than reported in published trial data of COMT inhibitor naïve patients.

Variations in hospitalization rates across Parkinson's Foundation Centers of Excellence

IntroductionPatients with Parkinson's disease (PD) are at increased risk for hospitalization and often experience worsening of PD when hospitalized. It is therefore important to identify strategies to prevent hospitalization. MethodsHospital encounter rates in different Parkinson's Foundation Centers of Excellence in United States, Canada, Israel and the Netherlands were analyzed as part of the Parkinson Foundation Parkinson's Outcomes Project (PF-POP). Multivariate logistic regression was used to estimate the odds ratio for hospitalization, adjusted for risk factors. ResultsBaseline age, disease duration, other relative than spouse/partner as care giver, cancer, arthritis, other comorbidities, falls, use of levodopa, use of dopamine agonist, use of COMT inhibitor, occupational therapy before the baseline visit, PDQ-39, MSCI total score and time between visits were significantly associated with the risk of hospital encounters. After adjustment for these factors, two centers had significantly lower odds for hospitalization admission and ER visit (minimum OR 0.3) and four centers had significantly higher odds (maximum OR 1.5) than the average center. Four centers had significantly lower hazard ratios for time to re-hospitalization compared to the average center. Reducing hospital admission rates in those centers with higher than average rates would reduce overall hospitalizations by 11%. Applied to PD patients over 65 nationwide this represents a potential for cost savings of greater than $1 billion over 48 months. ConclusionEncounter rates vary even across expert centers and suggest that practices carried out in some centers may reduce the risk of hospitalization. Further research will be necessary to identify these practices and implement them more widely to improve care for people with PD.

Efficacy and safety/tolerability of opicapone in catechol-O-methyltransferase inhibitor-naïve Parkinson's disease patients recently diagnosed with motor fluctuations

Background: To evaluate the potential added benefit of opicapone (OPC), versus placebo (PLC) and entacapone (ENT), in catechol-O-methyltransferase inhibitor (COMTi)-naïve Parkinson's disease (PD) patients from the BIPARK-I trial who were recently diagnosed with motor fluctuations ('recent fluctuators'; defined as having an onset of motor fluctuations < /=1 year of study baseline).

Prospecting for new catechol-O-methyltransferase (COMT) inhibitors as a potential treatment for Parkinson’s disease: a study by molecular dynamics and structure-based virtual screening

Parkinson’s disease (PD) is a neurodegenerative, chronic, and progressive disease, common in the elderly. The catechol-O-methyltransferase (COMT) is a monomeric enzyme involved in dopamine (DA) degradation, the neurotransmitter in deficit in patients with PD. The reference treatment of PD consists of levodopa (L-dopa) administration, which is the precursor of DA. The inhibition of COMT is an adjuvant treatment in PD since it keeps DA levels constant. The goal of this study was to identify drug candidates capable of inhibiting COMT for the treatment of PD and identify important fragments of these molecules. Initially, we analyzed the flexibility of COMT and defined its main conformations in solution regarding the absence (system I) and presence of the S-adenosyl-L-methionine (SAM) cofactor (system II) through molecular dynamics (MD) simulations. Two regions in these structures were selected for molecular docking, firstly the entire cavity where the cofactor and substrates are bound and secondly the specific biding region of the enzyme substrates. Based on the conformations of the MD, the virtual screening (VS) was performed against FDA Approved and Zinc Natural Products databases aiming at the selection of the best compounds. Subsequently, the absorption, distribution, metabolization, excretion, and toxicity (ADMET) properties, as well as drug-score and drug-likeness indexes of the most promising compounds were analyzed. After a detailed analysis of the compounds selected by structure-based VS, it was possible to highlight the fragments most frequently involved in their stability: 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole, 9H-Benz(c)indole(3,2,1-ij)(1,5)naphthyridin-9-one and (10R,13S)-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17dodecahydrocyclopenta[a]phenanthren-3-one. The identification of these potential fragments is essential for the prospection of more specific inhibitors against COMT using the technique of Fragment-based lead discovery (FBLD). Besides, this study allowed us to identify the potential COMT inhibitors through a complete understanding of molecular-level interactions based on the flexibility of this protein. Communicated by Ramaswamy H. Sarma

The catechol-O-methyltransferase inhibitor tolcapone modulates alcohol consumption and impulsive choice in alcohol use disorder

Individuals suffering from alcohol use disorder (AUD) demonstrate difficulty with decision-making and impulsivity that may be associated with impaired frontal cortical function. Therapeutics that enhance frontal dopamine tone could decrease impulsivity and in turn reduce alcohol consumption in individuals with AUD. To determine if the catechol-O-methyltransferase (COMT) inhibitor tolcapone can attenuate alcohol consumption in individuals with AUD and whether this attenuation correlates with tolcapone-induced changes in laboratory-based decision-making tasks. We used daily self-report and a novel group laboratory bar task to assess the effects of randomized double-blind crossover administration of tolcapone (100mg TID for 5days) on alcohol consumption and laboratory tasks assessing impulsivity in 55 non-treatment-seeking subjects with AUD. Tolcapone significantly reduced self-reported alcohol consumption (t (54) = 2.05, p = 0.045). The effects of tolcapone on drinking significantly correlated with changes in impulsive decision-making, such that subjects with the greatest decrease in impulsive choice on tolcapone also reported the greatest decrease in alcohol consumption (r (45) = 0.40, p = 0.0053). We did not see effects of tolcapone on laboratory bar consumption. Adverse event (AE) reporting was low, with no significant difference in frequency or severity of AEs on tolcapone versus placebo. These data demonstrate that COMT inhibitors such as tolcapone may be useful therapeutics for AUD. ClinicalTrials.gov Identifier: NCT02740582.

The role of inhibitors of COMT and MAO-B in the therapy of Parkinson's disease

Inhibitors of COMT and MAO-B are well established in the pharmacotherapy of Parkinson's disease (PD). MAO-B inhibitors are used as monotherapy as well as in combination with levodopa, whereas COMT inhibitors exert their effects only in conjungtion with levodopa. Both classes of compounds prolong the response duration of levodopa and optimise its clinical benefit. As a result, the ON-times are prolonged significantly. In the past, MAO-B inhibitors were also adminstered for neuroprotection; however, despite convincing scientific reasoning in support of neuroprotective effects, these could not be substantiated in clinical studies performed so far.

Novel, non-nitrocatechol catechol-O-methyltransferase inhibitors modulate dopamine neurotransmission in the frontal cortex and improve cognitive flexibility.

Cognitive impairment is a primary feature of many neuropsychiatric disorders and there is a need for new therapeutic options. Catechol-O-methyltransferase (COMT) inhibitors modulate cortical dopaminergic function and have been proposed as potential cognitive enhancers. Unfortunately, currently available COMT inhibitors are not good candidates due to either poor blood-brain barrier penetration or severe toxicity. To address the need for safe, brain-penetrant COMT inhibitors, we tested multiple novel compounds in a set of preclinical in vivo efficacy assays in rats to determine their ability to inhibit COMT function and viability as potential clinical candidates. We measured the change in concentration of dopamine (DA) metabolites in cerebrospinal fluid (CSF) from the cisterna magna and extracellular fluid (ECF) from the frontal cortex produced by our novel compounds. Additionally, we tested the effects of our brain-penetrant COMT inhibitors in an attentional set-shifting assay (ASST). We benchmarked the performance of the novel COMT inhibitors to the effects produced by the known COMT inhibitor tolcapone. We found that multiple COMT inhibitors, exemplified by LIBD-1 and LIBD-3, significantly modulated dopaminergic function measured as decreases in homovanillic acid (HVA) and increases in 3,4-Dihydroxyphenylacetic acid (DOPAC), two DA metabolites, in CSF and the frontal cortex. Additionally, we found thatLIBD-1 significantly improved cognitive flexibility in the ASST, an effect previously reported following tolcapone administration. These results demonstrate that LIBD-1 is a novel COMT inhibitor with promising in vivo activity and the potential to serve as a new therapy for cognitive impairment.

Parkinson's Disease: A Review from Pathophysiology to Treatment.

Parkinson's Disease (PD) is the second most common neurodegenerative disease in the elderly population, with a higher prevalence in men, independent of race and social class; it affects approximately 1.5 to 2.0% of the elderly population over 60 years and 4% for those over 80 years of age. PD is caused by the necrosis of dopaminergic neurons in the substantia nigra, which is the brain region responsible for the synthesis of the neurotransmitter dopamine (DA), resulting in its decrease in the synaptic cleft. The monoamine oxidase B (MAO-B) degrades dopamine, promoting the glutamate accumulation and oxidative stress with the release of free radicals, causing excitotoxicity. The PD symptoms are progressive physical limitations such as rigidity, bradykinesia, tremor, postural instability and disability in functional performance. Considering that there are no laboratory tests, biomarkers or imaging studies to confirm the disease, the diagnosis of PD is made by analyzing the motor features. There is no cure for PD, and the pharmacological treatment consists of a dopaminergic supplement with levodopa, COMT inhibitors, anticholinergics agents, dopaminergic agonists, and inhibitors of MAO-B, which basically aims to control the symptoms, enabling better functional mobility and increasing life expectancy of the treated PD patients. Due to the importance and increasing prevalence of PD in the world, this study reviews information on the pathophysiology, symptomatology as well as the most current and relevant treatments of PD patients.

Central nervous system activities of extract Mangifera indica L.

Ethnobotanical relevanceLeaves of Mangifera indica L. have folk-uses in tropical regions of the world as health teas, as a remedy for exhaustion and fatigue, as a vegetable, and as a medicine. Mangifera indica leaf extract (MLE) had previously been demonstrated to alter brain electrical activity in-vivo. The aim of the present series of studies was to investigate whether mangiferin, a major compound in leaves and in MLE, is responsible for the neurocognitive activity of MLE, and if the CNS activities of MLE have translational potential. Materials and methodsMLE, tradename Zynamite, is produced by Nektium Pharma, Spain. Isolated mangiferin was tested in-vitro in radioligand binding and enzyme inhibition studies against 106 CNS targets. Changes in the electroencephalograms (EEG’s) of MLE and mangiferin were recorded in-vivo from four brain regions. Two double blind randomized placebo-controlled crossover clinical trials were conducted, each with 16 subjects. At 90 min and at 60 min respectively, after oral intake of 500 mg MLE, EEG recordings, psychometric tests, mood state, and tolerability were studied. ResultsIsolated mangiferin is a selective inhibitor of catechol-O-methyltransferase (COMT) with an IC50 of 1.1 μM, with no activity on the CNS targets of caffeine. Both mangiferin and MLE induce similar changes in long-term potentiation (LTP) in the hippocampus in-vitro, and induce a similar pattern of EEG changes in-vivo. In both translational clinical trials MLE was well tolerated, with no cardiovascular side-effects. In both studies MLE caused significant spectral changes in brain electrical activity in cortical regions during cognitive challenges, different to the attenuated spectral changes induced by caffeine. There were no significant changes in the psychometric tests other than reaction time for all groups. In the second study there was a trend to faster reaction time within group for MLE (p = 0.066) and the percentage improvement in reaction time for MLE compared to placebo was significant (p = 0.049). In the first study MLE improved all scores for Profile of Mood States (POMS), with the score for “fatigue” significantly improved (p = 0.015); in the second study the POMS score for “dejection” was improved in the caffeine group, p = 0.05. ConclusionsMangiferin is a COMT inhibitor of moderate potency and is the major CNS-active compound in MLE. Both mangiferin and MLE increase hippocampal LTP in-vitro, and induce a similar pattern of changes in brain electrical activity in-vivo.While the translational clinical trials of MLE are limited by being single dose studies in a small number of subjects, they provide the first clinical evidence that the extract is well tolerated with no cardiovascular side-effects, can induce changes in brain electrical activity, may give a faster reaction time, and decrease fatigue.These CNS activities support the reported folk-uses use of mango leaf tea as a substitute for tea and as a traditional remedy for fatigue and exhaustion. Extract Mangifera indica L., Zynamite, has nootropic potential, and larger clinical studies are needed to realise this potential.