Lipid peroxidation (LP) is the most important type of oxidative-radical damage in biological systems, owing to its interplay with ferroptosis and to its role in secondary damage to other biomolecules, such as proteins. The chemistry of LP and its biological consequences are reviewed with focus on the kinetics of the various processes, which helps understand the mechanisms and efficacy of antioxidant strategies. The main types of antioxidants are discussed in terms of structure-activity rationalization, with focus on mechanism and kinetics, as well as on their potential role in modulating ferroptosis. Phenols, pyri(mi)dinols, antioxidants based on heavy chalcogens (Se and Te), diarylamines, ascorbate and others are addressed, along with the latest unconventional antioxidant strategies based on the double-sided role of the superoxide/hydroperoxyl radical system.

Chamazulene (CA) is an intensely blue molecule with a wealth of biological properties. In cosmetics chamazulene is exploited as a natural coloring and soothing agent. CA is unstable and tends to spontaneous degradation accelerated by light. We studied the photodegradation of CA upon controlled exposure to UVB-UVA irradiation by multi-ple techniques, including GC-MS, UHPLC-PDA-ESI-MS/MS and by direct infusion in ESI-MSn, which were matched to in silico mass spectral simulations to identify degra-dation products. Seven byproducts formed upon UVA exposure for 3 h at 70mW/cm2 (blue-to-green color change) were identified, including CA dimers and CA benzenoid which were not found on extended 6 h irradiation (green-to-yellow fading). Photosta-bility tests with reduced irradiance conducted in various solvents in the pres-ence/absence of air indicated highest degradation in acetonitrile in the presence of ox-ygen, suggesting a photo-oxidative mechanism. Testing in the presence of antioxidants (tocopherol, ascorbyl palmitate, hydroxytyrosol, bakuchiol, γ-terpinene, TEMPO and their combinations) indicated highest protection by tocopherol and TEMPO. Sun-screens ethylhexyl methoxycinnamate and particularly Tinosorb® S (but not octo-crylene) showed good CA photoprotection. Thermal stability tests indicated no degra-dation of CA in acetonitrile at 50°C in the dark for 50 days; however, accelerated deg-radation occurred in the presence of ascrorbyl palmitate.