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. 2023 Nov;102(5):1067-1074.
doi: 10.1111/cbdd.14304. Epub 2023 Jul 27.

The evaluation of isatin analogues as inhibitors of monoamine oxidase

Izak F Prinsloo  1 , Jacobus P Petzer  1 , Theunis T Cloete  1 , Anél Petzer  1
Affiliations

The evaluation of isatin analogues as inhibitors of monoamine oxidase

Izak F Prinsloo et al. Chem Biol Drug Des. 2023 Nov.

Abstract

The small molecule, isatin, is a well-known reversible inhibitor of the monoamine oxidase (MAO) enzymes with IC50 values of 12.3 and 4.86 μM for MAO-A and MAO-B, respectively. While the interaction of isatin with MAO-B has been characterized, only a few studies have explored structure-activity relationships (SARs) of MAO inhibition by isatin analogues. The current study therefore evaluated a series of 14 isatin analogues as in vitro inhibitors of human MAO-A and MAO-B. The results indicated good potency MAO inhibition for some isatin analogues with five compounds exhibiting IC50 < 1 μM. 4-Chloroisatin (1b) and 5-bromoisatin (1f) were the most potent inhibitors with IC50 values of 0.812 and 0.125 μM for MAO-A and MAO-B, respectively. These compounds were also found to be competitive inhibitors of MAO-A and MAO-B with Ki values of 0.311 and 0.033 μM, respectively. Among the SARs, it was interesting to note that C5-substitution was particularly beneficial for MAO-B inhibition. MAO inhibitors are established drugs for the treatment of neuropsychiatric and neurodegenerative disorders, while potential new roles in prostate cancer and cardiovascular disease are being investigated.

Keywords: competitive; inhibition; isatin; monoamine oxidase; structure-activity relationship.

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