Pregnenolone derivatives for the treatment of Alzheimer's disease: synthesis, and in vitro inhibition of amyloid β1–42 peptide aggregation, acetylcholinesterase and carbonic anhydrase-II

The amyloid state, which is a specific conformation of proteins, offers valuable information about both functional protein structures and the pathological assemblies associated with various diseases. One of the major hallmarks of Alzheimer's disease includes primarily the extracellular build-up of a peptide known as amyloid-β, which has a sequence consisting of 39 to 42 amino acid residues, and the formation of intracellular neurofibrillary tangles mostly consisting of hyperphosphorylated tau protein. Drugs that are expected to reduce Aβ production, prevent Aβ aggregation, and promote Aβ clearance are promising approaches for treating AD. Current work is focused on identifying the compounds that have balanced even mild biological activities against multiple targets instead of finding one-target compound with high potency. We synthesized pregnenolone derivatives and evaluated their potential against inhibition of eeAChE/eqBChE, hCA-II and self-mediated Aβ1–42 peptide aggregation. Our synthesized derivatives 23, and 25–27 exhibited concomitant inhibition of all the tested macromolecular targets. All the active compounds were found to be BBB penetrants in the PAMPA assay. Furthermore, these selected compounds were found to be non-neurotoxic in the MTT assay on neuroblastoma SH-SY5Y cells. Docking studies support dual binding site (PAS and CAS) inhibition of AChE which showed Aβ1–42 aggregation and AChE inhibition. Moreover, docking studies carried out on the 3D crystallographic structure of Aβ1–42 peptide (PDB ID = 1IYT) showed significant interactions with amino acid residues Asp 23 and Lys 28, and hydrophobic interactions with the Phe19, Phe20, and Ala 30 effectively impeding the formation of β-sheet structures.