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Thread: Quercetin as a MAO-B inhibitor in prevention of MDMA neurologic side effects?

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    Quercetin as a MAO-B inhibitor in prevention of MDMA neurologic side effects? 
    #1
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    http://en.wikipedia.org/wiki/Quercet...dase_inhibitor

    It inhibits MAO-A (very bad) but mostly MAO-B, with 100x selectivity for MAO-B, which means there should exist a pretty wide range of dosages with MAO-B inhibition and no MAO-A inhibition. I have no ability to interpret those IC50 values and what they translate to in terms of dosage, though, so I would definitely not advise going out and taking quercetin with your ecstasy, at least not yet.

    As an added bonus, it's a decently effective antioxidant.
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    Micromolar MAO concentrations are pretty lame, pharmaceutically speaking. Unless you're taking grams and grams of the pure compound, & it builds up in the brain.

    Piperine competitively inhibited MAO-A and MAO-B with Ki values of 19.0+/-0.9 microM and 3.19+/-0.5 microM,
    Quercetin has also been shown to [inhhibit] MAO-A (IC50 = 18 +/-0.2 microM) and especially MAO-B (IC50 = 0.2 +/-0.02 microM)
    Rosiridin inhibits MAO-B at approx. 10 micromolar concentrations.

    IC50 (required concentration to inhibit 50% of the enzyme) for segeligine: 1.7 uM (1700 nM) for MAO-A, and 6.8 nM for MAO-B

    Quercertin is therefore approximately 1/30 as effective as a MAO-B inhibitor as selegiline, mole for mole (sp). The flavonoids are actually pretty crappy MAOI's because they are very water soluble and easily metabolised, so I doubt it's going to produce a MAOI effect at human doses.

    Refs: me, wikipedia, pubmed.
    Last edited by sekio; 01-11-2013 at 23:48. Reason: typos
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    Although quercetin doesn't seem like a great MAOI, in terms of the original proposition, there still might be some reason to think that it could potentiate (or even inhibit) the effects of MDMA. From memory, and from a cursory literature scan, it seems that quercetin is a decent P-gp inhibitor and a CYP3A4 inhibitor. Very many drugs (especially those that are metabolized by CYP3A4, like MDMA is partially) are ligands for P-gp, or p-glycoprotein, a protein found on the intestinal walls that transports drugs from the inside of small intestine epithelial cells back into the small intestine. Functionally, this means that drug absorbed by those cells is spit back out into the intestines and any that has been absorbed earlier or by other means and has come through the blood back into intestinal epithelial cells is then excreted by this efflux mechanism. P-gp inhibitors can enhance absorption of some drugs and increase the lifespan in the body by blocking this efflux mechanism.

    In addition, blocking metabolism of MDMA with a CYP3A4 inhibitor might have some potentiation effect on MDMA or at least increase the duration of the peak. Of course MDMA is always more complex than one thinks and things like this tend to have the opposite effect, because it seems that MDMA metabolism might be critical for eliciting the full range of its positive effects and of course keeping a likely neurotoxic drug around in the body longer and blocking two clearance mechanisms is generally not great. But interestingly, quercetin also seems to induce CYP3A4 expression over a longer period than its blockade mechanism, so the problems may be nullified or if you had taken it far in advance, it might have the opposite 3A4 effects. Anyone have any other thoughts about all this?
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