The interactions of azure B, a metabolite of methylene blue, with 2 acetylcholinesterase and butyrylcholinesterase
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Elsevier
Abstract
Methylene blue(MB) is reported to possess diverse pharmacological actions and is attracting increasing attention
for the treatment of neurodegenerative disorders such as Alzheimer's disease. Among the pharmacological
actions of MB, is the significant inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE).
These activities may, at least in part, underlie MB's beneficial effects in Alzheimer's disease. MB is metabolized
to yield N-demethylated products of which azure B, the monodemethyl metabolite, is the predominant species.
Azure B has been shown to be pharmacologically active and also possesses a variety of biological actions. Azure B
therefore may contribute to the pharmacological profile of MB. Based on these considerations, the present study
investigates the possibility that azure B may, similar to MB, act as an inhibitor of human AChE and BuChE. The
results document that azure B inhibits AChE and BuChE with IC50 values of 0.486 μM and 1.99 μM, respectively.
The results further show that azure B inhibits AChE and BuChE reversibly, and that the modes of inhibition are
most likely competitive. Although the AChE and BuChE inhibitory activities of azure B are twofold and fivefold,
respectively, less potent than those recorded for MB [IC50(AChE)=0.214 μM; IC50(BuChE)=0.389 μM] under
identical conditions, azure B may be a contributor to MB's in vivo activation of the cholinergic system and
beneficial effects in Alzheimer's disease.
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Citation
Petzer, A. et al. 2014. The interactions of azure B, a metabolite of methylene blue, with 2 acetylcholinesterase and butyrylcholinesterase. Toxicology and applied pharmacology, 274(3):488-493. [https://doi.org/10.1016/j.taap.2013.10.014]