Rational design of tetrahydrotetrazinones as potent nonclassical radical-trapping antioxidants for inhibition of ferroptosis.

Radical-trapping antioxidant (RTA) protection plays a critical role in industrial, biological, and pharmaceutical contexts. The cytoprotective role of RTAs has been increasingly recognized as essential in regulating ferroptosis, a form of regulated cell death driven by lipid peroxidation. However, current ferroptosis inhibitors primarily rely on phenolic or aromatic amine scaffolds, which were found through high-throughput screening or derived from historically known RTAs. We introduce hydrazine-derived tetrahydro-1,2,4,5-tetrazin-3-ones (THTZOs) as a class of nonclassical RTAs. THTZOs operate via a unique mechanism involving hydrazyl and verdazyl radical intermediates that is independent of aromatic stabilization. These compounds demonstrate broad reactivity against autoxidation in both simple hydrocarbons and membrane phospholipids, effectively suppressing ferroptosis induced by RAS-selective lethal 3 (RSL3) or erastin in multiple cell lines. Our findings revitalize the application of hydrazine derivatives in RTA chemistry and establish a foundation for the rational design of RTAs as potent ferroptosis inhibitors, offering previously unidentified antioxidant therapeutic candidates.