Herbal Natural Products As a Source of Monoamine Oxidase Inhibitors: A Review

Dipartimento di Scienze della Vita e dell'Ambiente, Facoltà di Farmacia, Università degli Studi di Cagliari, 09124-Cagliari, Italy. .
Current topics in medicinal chemistry (Impact Factor: 3.4). 11/2012; 12(20). DOI: 10.2174/1568026611212200003
Source: PubMed


Drugs of natural origin still play a major role in the treatment of many diseases and as lead structures for the development of new synthetic drug substances. This review article deals the pharmacological effects on the Central Nervous System (CNS) of some plant extracts and their isolated chemical components due to their monoamine oxidase (MAO) activity. Herbs and herbal preparations containing MAO-A inhibitors have been widely used as an effective alternative in the treatment of neuropsychiatric diseases such as depression. Inhibitors of MAO-B not only enhance dopaminergic neurotransmission but also prevent activation of toxin and free radical formation, alleviating the process of neuron denaturalization, on account of which they are used in Parkinson disease (PD). Several methods have been developed for monitoring MAO activity and its inhibitor screening of bioactive natural products.

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    ABSTRACT: Monoamine oxidases (MAOs) are mitochondrial bound enzymes, which catalyze the oxidative deamination of monoamine neurotransmitters. Inside the brain, MAOs are present in two isoforms: MAO-A and MAO-B. The activity of MAO-B is generally higher in patients affected by neurodegenerative diseases like Alzheimer's and Parkinson's. Therefore, the search for potent and selective MAO-B inhibitors is still a challenge for medicinal chemists. Nature has always been a source of inspiration for the discovery of new lead compounds. Moreover, natural medicine is a major component in all traditional medicine systems. In this review, we present the latest discoveries in the search for selective MAO-B inhibitors from natural sources. For clarity, compounds have been classified on the basis of structural analogy or source: flavonoids, xanthones, tannins, proanthocyanidins, iridoid glucosides, curcumin, alkaloids, cannabinoids, and natural sources extracts. MAO inhibition values reported in the text are not always consistent due to the high variability of MAO sources (bovine, pig, rat brain or liver, and human) and to the heterogeneity of the experimental protocols used.
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    ABSTRACT: Desmodeleganine (1), a new potential monoamine oxidase inhibitor, along with three known alkaloids, bufotenin (2), hydroxy-N, N-dimethyltryptamine N(12)-oxide (3), 2-(5-methoxy -1H-indol-3-yl)-N, N-dimethylethylamine (4) were isolated from the leaves of Desmodium elegans. Their structures were elucidated by IR, MS, 1D- and 2D-NMR spectra. 1 showed strong monoamine oxidase inhibitory activity with IC50 value of 13.92±1.5μM, when the IC50 value of iproniazid as a standard was 6.5±0.5μM. The molecular modeling was also performed to explore the binding mode of compounds 1, 2 at the active site of MAO-A and MAO-B.
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