Synthesis and preformulation studies of natural-inspired antioxidant hybrids with neuroprotective or antiproliferative activity

This PhD thesis focuses on the design and synthesis of novel hybrid compounds inspired by natural antioxidants with potential antiproliferative or neuroprotective activities. The research is based on a fragment-based molecular hybridization strategy that combines pharmacophoric motifs relevant in medicinal chemistry, in which at least one fragment is a natural antioxidant product (e.g., coumarin, vanillin, isovanillin, cinnamic acids or cytisine) or one of their synthetic derivatives. This approach aims to generate compounds with polypharmacological profiles capable of modulating cancer-related pathways as well as biological targets involved in the neurodegenerative processes associated with Alzheimer’s disease (AD). A total of 150 final compounds were synthesized, including 64 derivatives (compounds 1–64) investigated for antiproliferative activity and 86 compounds (65–150) designed as potential anti-AD agents. The chemical radical scavenging activity of each compound was assessed by DPPH assay, revealing structural features-dependent variations. In the anticancer section, two main series were developed: vanillin/isovanillin-based hydrazone hybrids and 3-cinnamoyl coumarins. Several hydrazone derivatives showed strong growth-inhibitory effects in a neuroblastoma cellular model, including in chemotherapy-resistant cells. One compound in particular reduced tumor cell proliferation while sparing non-malignant cells; mechanistic studies indicated that its activity was associated with increased ROS production, induction of cellular senescence, and reduced clonogenic potential. Moreover, micellar encapsulation using non-ionic surfactants improved the aqueous solubility of one of the most active but poorly soluble candidates. The 3-cinnamoyl coumarin series also displayed a favorable antiproliferative profile against breast and lung cancer cell lines, with several derivatives showing activity in the low micromolar range. The anti-AD section explored a library of sixty coumarin-based multitarget ligands incorporating alicyclic amines. Several derivatives showed potent cholinesterase inhibition, with submicromolar activity and tunable selectivity depending on linker length and amine fragment. All compounds of this series were also evaluated for their ability to inhibit Aβ42 self-aggregation during a six-month research internship at the University of Cambridge (UK). Additional scaffold combinations (phenothiazine–cinnamic acids, cytisine–cinnamic acids, and coumarin–indole hybrids) were investigated to expand the chemical diversity of the anti-AD library. Among these, the coumarin–alicyclic amine and phenothiazine–cinnamic acid series yielded compounds with promising polypharmacological profiles, selected for further evaluation of their neuroprotective potential in cellular models. Overall, these results support molecular hybridization of natural-inspired scaffolds as an effective strategy to obtain bioactive compounds and provide useful structure–activity relationship insights for the future optimization of multitarget agents for cancer and AD.