Novel Isatin Thiosemicarbazone Derivatives as Potent Inhibitors of β-Amyloid Peptide Aggregation and Toxicity

Abstract

Inhibition of β-amyloid peptide (Αβ) aggregation in Alzheimer’s disease (AD) is among the therapeutic approaches against AD which still attracts scientific research interest. In the search for compounds that interact with Aβ and disrupt its typical aggregation course toward oligomeric or polymeric toxic assemblies, small organic molecules of natural origin, combining low molecular weight (necessary blood-brain barrier penetration) and low toxicity (necessary for pharmacological application), are greatly sought after. Isatin (1H-indoline-2,3-dione), a natural endogenous indole, and many of its derivatives exhibit a wide spectrum of neuropharmacological and chemotherapeutic properties. The synthesis and biological evaluation of four new isatins as inhibitors of Aβ aggregation is presented herein. In these derivatives, the N-phenyl thiosemicarbazide moiety is joined at the 3-oxo position of isatin through Schiff base formation, and substitutions are present at the indole nitrogen and position 5 of the isatin core. Biophysical studies employing circular dichroism, thioflavin T fluorescence assay, and transmission electron microscopy reveal the potential of the isatin thiosemicarbazones (ITSCs) to alter the course of Αβ aggregation, with two of the derivatives exhibiting outstanding inhibition of the aggregation process, preventing completely the formation of amyloid fibrils. Furthermore, in in vitro studies in primary neuronal cell cultures, the ITSCs were found to inhibit the Aβ-induced neurotoxicity and reactive oxygen species production at concentrations as low as 1 μM. Taken all together, the novel ITSCs can be considered as privileged structures for further development as potential AD therapeutics.

Exploration of the Detailed Structure–Activity Relationships of Isatin and Their Isomers As Monoamine Oxidase Inhibitors

“… 15 − 24 Many drugs have recently been reported for the treatment of renal cell carcinoma and imatinib-resistant gastrointestinal stromal tumors like Sunitinib. 25 − 27 …”

The Prophylactic and Multimodal Activity of Two Isatin Thiosemicarbazones against Alzheimer’s Disease In Vitro

“…The ITSCs derivatives M and FMp were synthesized in high yielding reactions and fully characterized by spectroscopic methods (IR, MS and NMR), as previously described [ 25 ].…”

“…Based on all the aforementioned evidence, we would like to report herein on an investigation into the potentially prophylactic and multimodal mode of action of two isatin thiosemicarbazone (ITSC) derivatives, namely M and FMp ( Figure 1 ). The compounds have been synthesized by our group and previously shown to inhibit Aβ aggregation [ 25 ]. In this work, the exogenous Aβ-mediated toxicity at different time points of pre- or post-incubation of the compounds in the SK-N-SH cell line were thoroughly investigated.…”

A Review on Isatin and Its Derivatives: Synthesis, Reactions and Applications

“…The indole moiety in this compound is made up of a pyrrolidine ring fused to benzene to form 2, 3-dihydro indole. It is a monoamino oxidase inhibitor that's been detected in high concentrations in the urine of Parkinson's patients [2][3][4][5][6]. In the field of heterocyclic and pharmaceutical chemistry, isatins are useful intermediates [7,8].…”