Numerous small molecules have been studied for their
ability to
counteract oxidative stress, a key contributor to neurodegenerative
diseases such as Alzheimer’s. Despite these efforts, the pharmacological
properties and structure–activity relationships of these compounds
remain insufficiently understood, yet they are critical in evaluating
a drug molecule’s therapeutic potential. A modified tetra-aza
macrocycle has demonstrated strong antioxidant activity through various
mechanisms; however, its limited permeability presents challenges
for advanced formulation studies. To enhance permeability while preserving
the beneficial reactivity of the parent molecule, two synthetic modifications
involving indole functionality were explored and compared to modifications
using methyl groups alone. New synthetic strategies were developed
to produce the indole-containing molecules, which were characterized
by 1D/2D NMR techniques. Isoelectric points, metal binding, and radical
scavenging activity were determined to validate that the reactivity
of the parent molecules was retained. The permeability of all molecules
explored was improved. Protection against oxidative stress through
activation of the Nrf2 pathway was demonstrated for molecules containing
indoles in cellular models by measuring ROS levels upon treatment
and mRNA levels of HO-1 and Nrf2. In contrast, no protection or Nrf2
activation was observed with the methylation of the O- or N atom.
These results suggest that while alkylation improves permeability
overall, concomitant antioxidant protection and positive permeability
are achieved with the indole congeners alone.