New mescaline-related N-acylhydrazone and its unsubstituted benzoyl derivative: Promising metallophores for copper-associated deleterious effects relief in Alzheimer's disease.

Two new synthetic compounds, X1TMP and X1Benz, designed to bind copper(II), were tested for their effects on processes linked to Alzheimer's disease. Both compounds reduced the production of reactive oxygen species (ROS) by the copper-amyloid-β system and prevented the aggregation of amyloid-β peptides into fibrils, as shown by turbidity measurements and electron microscopy. Nuclear magnetic resonance experiments revealed that X1Benz interacts directly with amyloid-β and, unexpectedly, forms a three-part complex with copper and the peptide, which may explain its ability to lessen ROS and inhibit aggregation. The compounds show promise as potential therapeutic agents for Alzheimer's disease.

Study at a glance

Abstract

Alzheimer's disease (AD) is related to the presence of extracellular aggregated amyloid-β peptide (Aβ), which binds copper(II) with high affinity in its N-terminal region. In this sense, two new 1-methylimidazole-containing N-acylhydrazonic metallophores, namely, X1TMP and X1Benz, were synthesized as hydrochlorides and characterized. The compound X1TMP contains the 3,4,5-trimethoxybenzoyl moiety present in the structure of mescaline, a natural hallucinogenic protoalkaloid that occurs in some species of cacti. Single crystals of X1Benz, the unsubstituted derivative of X1TMP, were obtained. The experimental partition coefficients of both compounds were determined, as well as their apparent affinity for Cu2+ in aqueous solution. Ascorbate consumption assays showed that these N-acylhydrazones are able to lessen the production of ROS by the Cu(Aβ)-system, and a short-time scale aggregation study, measured through turbidity and confirmed by TEM images, revealed their capacity in preventing Aβ fibrillation at equimolar conditions in the presence and absence of copper. 1H15N HSQC NMR experiments demonstrated a direct interaction between Aβ and X1Benz, the most soluble of the compounds. The Cu2+ sequestering potential of this hydrazone towards Aβ was explored by 1H NMR. Although increasing amounts of X1Benz were unexpectedly not efficient at removing the metal-induced perturbations in Aβ backbone amides, the broadening effects observed on the compound's signals indicate the formation of a ternary Aβ‑copper-X1Benz species, which can be responsible for the observed ROS-lessening and aggregation-preventing activities. Overall, the N-acylhydrazones X1TMP and X1Benz have shown promising prospects as agents for the treatment of AD.