Guaiazulene-based phenolic radical scavengers: synthesis, properties, and EPR studies of their reaction with oxygen-centred radicals

A variety of phenolic derivatives , carrying the guaiazulene moiety, were prepared starting from guaiazulene. Compounds react with oxygen-centred radicals exhibiting chromotropic behaviour. The radical scavenging power of these compounds was evaluated by different methods. Compounds are less efficient than some of the most common radical scavengers but show quite selective behaviour towards different oxygen-centred radicals. A correlation is found between the antioxidant activity of the compounds and the corresponding phenolic O–H bond dissociation energy. Some aspects of the reaction of the compounds with oxygen-centred radicals were elucidated by EPR and DFT studies.