Why We Should Be Interested In Natural MAO Inhibitors

Why We Should Be Interested in Natural MAO Inhibitors

MAO stands for monoamine oxidase.

It's an enzyme that breaks down certain neurotransmitters in the brain like dopamine, serotonin, and dimethyltryptamine. All of which are crucial to brain function in various ways.

There are actually 2 types of MAO in the body, and although similar, have different preferences for the monoamines they break down (deaminate). MAO-A, and MAO-B.

Inhibiting this enzyme slows the breakdown of neurotransmitters, allowing their numbers to increase.

This can offer many benefits to both cognitive function, as well as psychological disorders like depression and anxiety.


Monoamine Neurotransmitters Include:

  • Dopamine
  • Serotonin
  • Adrenalin
  • Dimethyltryptamine (DMT)
  • Melatonin
  • Noradrenalin
  • B-phenylethylamine (PEA)
  • Benzylamine

MAO And Neurological Disease

An increase in monoamine oxidase has been shown to have a correlation with age-related cognitive disorders [2].

Increased levels of MAO-B, for example, has been closely associated with the development of Alzheimer’s disease, Huntington’s disease, some forms of Parkinson’s disease and normal aging [3], while increased MAO-A has been associated closely with depression, anxiety and psychiatric disorders [4].

The reason MAO tends to increase with age is not yet well understood.


Why We Need New MAO Inhibitors

The use of MAO inhibitors has been found to alleviate many of the symptoms of neurological disorders and is becoming a more valuable method of prevention and treatment as time goes on [6].

The downside to MAO inhibition is the adverse side effects that often come along with their long term use [7].

This has lead us to a point where it is clear that we need new, safer MOA inhibitors.

Fortunately, in recent years, there have been several plant-based MAO inhibitors that have so far shown low side effects, despite therapeutic doses of MAO inhibition.


MAO Inhibition And Nootropics

There is a growing trend of MAO inhibitors (generally plant-based)finding there way into nootropic formulas. The idea is that with a reduction in MAO, neurotransmitters and other monoamines found in the nootropic formulas will have a more prolonged effect.

Additionally, over more extended periods, the MAO intake will improve the overall effect of the nootropic on monoamine neurotransmitters in the brain.

A common mechanism for nootropics is to improve the production of various neurotransmitters. Therefore, inhibition of the enzymes that destroy them is likely to have a synergistic action on the overall effect.

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Bioprospecting Plant-Based MAO Inhibitors

Bioprospecting is the act of seeking out new medicines and commercial compounds from plant and animal species.

Here we highlight a few plants that have been found to have marked MAO inhibiting properties. 

Botanical MAO Inhibitors: 

licorice root.jpg

1. Amur Cork Tree (Phellodendron amurense)

MAO-B Inhibition Very High (IC50 <.07 mg/ml)

Amur cork tree is one of the 50 fundamental Chinese herbs. It's commonly used for it's sedative, muscle relaxant, antiarrhythmic, positive inotropic, hypotensive, and antibacterial actions. 

2. Gan Cao (Glycyrrhiza uralensis root)

MAO-B Inhibition Very High (IC50 <.07 mg/ml)

Gan Cao is a type of licorice (same genus), and is used in much the same way. Its traditional uses involves female disorders, digestive disorders, ulcers, and heart arryhtmias. One of the most interesting sue of this plant, is as a "harmonizer" of other medicinal plants. In Chinese traditional medicine this is one of the main herbs used in formulas for its ability to improve the outcomes of other plants.

3. Psoralea Fruit Babchi (Psoralea corylifolia)

MAO-B Inhibition Very High (IC50 <.07 mg/ml)

Psorlea fruit is a lesser known Ayurvedic and Traditional Chinese medicinal plant species. It was used in the past for conditions like vitiligo and other skin related conditions. Recently it has received a lot of attention for its MAO inhibiting properties, and is suggested to be a norepinephrine, re-uptake inhibitor.  

4. Licorice Root (Glycyrrhiza glabra)

MAO-B Inhibition Very High (IC50 <0.07 mg/ml)

Licorice and Gan Cao are very similar and have virtually the same uses. Licorice was often added to Chinese formulas for its ability to imporve the actions of the other herbs in the formula. 

5. Bakuchi Seed (Cyamopsis psoralioides)

MAO-B Inhibition Very High (IC50 <0.07 mg/ml)

The seed oil of Bakuchi is mainly used for treating skin and muscle damage. It's an old Ayurvedic herb with a long history of use and a long list of traditional uses in the body. 


Some Honourable Mentions:


1. Black Pepper (Piper negrum)

MAO-B Inhibition High (IC50 <0.2 mg/mL)

The black pepper extract piperine is a common addition to herbal and pharmaceutical medicines for its ability to dramatically improve intestinal absorption. Interestingly, piperine is also at least one of the components of black pepper shown to inhibit MAO-B. [7].


2. Green Tea (Camellia sinensis)

MAO-B Inhibition High (IC50 <.2 mg/ml)

Green tea (Camellia sinensis) is by far one of the most popular health beverages on the planet.

The health benefits of green tea are long and highly dependant on the way the harvested plant has been harvested and processed. In the study quotes for this MAO inhibitor data, the chosen product was Chinese Gunpowder Green Tea. 


3. Kava Kava (Piper methysticum)

MAO-B Inhibition High (IC50 <.2 mg/ml)

Kava (Piper methysticum) is most popular for its use as an anxiolytic.

It’s a common trick among public speakers to take a shot of kava kava extract before entering the stage.

It is perfect for those affected by anxiety disorders, and is used my many to calm down during stressful events or in the event of insomnia.


4. Lady's Mantle (Alchemilla vulgaris)

MAO-B Inhibition High (IC50 <.2 mg/ml)

Lady's Mantle (Alchemilla vulgaris) is most commonly used to slow or stop bleeding, whether topically or internally. it has also been used as a muscle relaxant and anticonvulsant. 


5. Turmeric (Curcuma Longa)

MAO-B Inhibition High (IC50 <.2 mg/ml)

Turmeric is one of the most well known, and popular herbs world wide. It's a main ingredient in curry, and a popular anti-inflammatory. It has a long list of uses, including antidepressant, hypotensive, cardiac tonic, antibacterial, and anti-arthritic. 


Conditions That May Benefit From MAO Inhibitor Use

1. Parkinson's Disease

Parkinson's disease is a condition related to low levels of dopamine. Much of this originates from the actual production of dopamine, and its release from the hypothalamus, but can also be affected by the enzymatic breakdown.

The modern treatment of Parkinson's disease usually involves an MAO-B inhibitor, along with L-Dopa in an attempt to increase dopamine levels in the brain [1]. Due to the common side effects of synthetic MAO inhibitors, the therapeutic use of naturally derived MAO inhibitors should be considered for closer examination with long-term randomized clinical trials.

2. Depression

Depression is another condition brought on by reduced neurotransmitter levels, particularly serotonin. Pharmaceutical medications like serotonin reuptake inhibitors (SSRIs) are most commonly used to prevent the reuptake of serotonin into the neuron.

By preventing this from happening, serotonin has a better chance of being reused, thus maximizing its effectiveness.

This is beneficial in conditions of depression where serotonin is the main causative factor of the condition. With MAOs, this can be further optimized by inhibiting the extracellular breakdown of serotonin as well as its reuptake.

3. Cognitive Enhancement

One of the main uses for MAO inhibitors is in nootropic formulas or nootropic stacks that work off dopamine or serotonin receptors. They allow some synergy to prevent the breakdown of the improved serotonin or dopamine production nudged by other aspects in the nootropic stack.

Piperine, commonly found in the product Bioperine, is a highly beneficial addition to nootropic supplements for both its MAO inhibition activity, as well as its ability to improve the bioavailability through the intestinal tract directly.

MAO inhibitors are used mainly to optimise the effectiveness of the nootropic formula, rather than cause nootropic action on their own. After reviewing the evidence put forth in this article however, it's likely that MAO inhibition on it's own has nootropic potential.

4. Ayahuasca

Ayahuasca is another interesting use of MAO inhibition. The ayahuasca brew, which is a psychedelic plant decoction used by Amazonian shamans, is a combination of dimethyltryptamine (DMT), and an MAO inhibitor.

The combination of MAO inhibitor (from Banisteriopsis capi) and a plant high in DMT allows for maximum effects of the DMT to take place.

DMT is a monoamine neurotransmitter and is quickly broken down by enzymes in the intestinal tract.

Interestingly enough, DMT is also the same molecule that is thought to cause dreaming while we sleep. By inhibiting the breakdown of this molecule, it can persist and cause the desired effects.


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Justin Cooke, BHSc

The Sunlight Experiment

(Updated May 2019)


Recent Blog Posts:


  1. Mazzio, E., Deiab, S., Park, K., & Soliman, K. F. A. (2013). High throughput screening to identify natural human monoamine oxidase B inhibitors. Phytotherapy Research, 27(6), 818-828.

  2. Symposium on Monoamine Oxidase and its Inhibition, & Bernheim, M. (1976). Monoamine oxidase and its inhibition : In honour of Mary L.C. Bernheim (Ciba Foundation symposium, 39 (new ser.); Ciba Foundation, new ser., 39). Amsterdam: Elsevier/Excerpta Medica/North-Holland. http://site.ebrary.com/id/10575452

  3. Rehman HU, Masson EA. Neuroendocrinology of ageing. Age
    Ageing 2001; 30: 279–87

  4. Jean CS. Cloning, after cloning, knock-out mice, and physiological
    functions of MAO A and B. Neurotoxicology 2004; 25:

  5. Guang, H., & Du, G. (2006). High-throughput screening for monoamine oxidase-A and monoamine oxidase-B inhibitors using one-step fluorescence assay. Acta Pharmacologica Sinica, 27(6), 760-6. doi:http://dx.doi.org.ezproxy.laureate.net.au/10.1111/j.1745-7254.2006.00336.x

  6. Yam ada M, Yasuhara H. Pharmacology of MAO inhibitors: safetyand future. Neurotoxicology 2004; 25: 215–21.

  7. Kong, L. D., Cheng, C. H., & Tan, R. X. (2004). Inhibition of MAO A and B by some plant-derived alkaloids, phenols and anthraquinones. Journal of Ethnopharmacology, 91(2), 351-355.