Optimization of pyrimidinol antioxidants as mitochondrial protective agents: ATP production and metabolic stability

Previously we described a novel series of pyrimidinol antioxidants and their structural optimization as potential therapeutic agents for neurodegenerative and mitochondrial disorders. Our initial lead compound was a potent antioxidant in vitro, but was subsequently found to exhibit poor stability to oxidative metabolism. The current study focused on balancing potency with metabolic stability through structural modification, and involved modifications at positions 2 and 4 of the pyrimidinol redox core, likely sites of oxidative metabolism. Eight new analogues have been prepared and their ability to suppress lipid peroxidation and reactive oxygen species (ROS), and to preserve mitochondrial membrane potential (Δψ_m) and support ATP production, has been investigated. The metabolic stability of the prepared compounds was also assessed in vitro using bovine liver microsomes to obtain preliminary insight on this class of compounds. This study revealed the complexity of balancing reasonable metabolic stability with efficient antioxidant properties. While a few analogues appear promising, especially in terms of metabolic stability, a 4-isopropoxy derivative conserved the favorable biological activity and exhibited good metabolic stability. The favorable metabolic stability conferred by the combination of the azetidine and isopropoxy moieties in analogue 6 makes this compound an excellent candidate for further evaluation.