Selective monoamine oxidase B inhibition by an Aphanizomenon flos-aquae extract and by its constitutive active principles phycocyanin and mycosporine-like amino acids

Aphanizomenon flos-aquae (AFA) is a fresh water unicellular blue-green alga that has been traditionally used for over 25 years for its health-enhancing properties. Recent studies have shown the ability of a proprietary AFA extract (Klamin®) to improve mood, counteract anxiety, and enhance attention and learning. Aim of this study was to test the monoamine oxidase (MAO) inhibition activity of the same AFA extract and of its constituents phycocyanin (AFA-PC) and mycosporine-like aminoacids (AFA-MAAs). All compounds showed a dose-dependent selective inhibition of MAO-B activity as compared to MAO-A. The IC50 values of the AFA extract (concentration 10 mg/ml), AFA-PC and AFA-MAAs were 6.4 μl/ml, 1.33 μM and 1.98 μM, respectively, evidencing a mixed-type of inhibition for the AFA extract (Ki 0.99 μl/ml), a non-competitive inhibition for AFA-PC (Ki 1.06 μM) and a competitive inhibition for AFA-MAAs (Ki 0.585 μM). These results are important to explain the neuromodulating properties of the AFA extract Klamin®, which is rich in phenylethylamine, a general neuromodulator, that would nevertheless rapidly destroyed by MAO-B enzymes without the inhibitory activity of the synergic active principles AFA-PC and AFA-MAAs. The present investigation thus proposes the extract as potentially relevant in clinical areas such as mood disorders and neurodegenerative diseases.