Oxidative stress is characterized by an imbalance between the overproduction of reactive prooxidant species by inflammatory cells, and an incapacity of the body’s antioxidant systems to counteract their adverse effects. This condition often results in increased tissue damage and chronic diseases (e.g. rheumatoid arthritis). 2-Styrylchromones and chalcones are two classes of naturally occurring chromones with interesting scaffolds for drug design, but, as far as we know, their antioxidant potential has never been compared using the same methodologies. The ability of seven structurally related hydroxylated 2-styrylchromones and chalcones to scavenge physiological relevant reactive oxygen [hydrogen peroxide (H₂O₂), superoxide anion radical (O₂^•―)] and nitrogen [nitric oxide (^•NO)] species was assessed using specific chemiluminescent (lucigenin), colorimetric (NBT) and fluorescent (DAF-2) probes.

From the studied hydroxylated compounds, only one 2-styrylchromone was active, scavenging O₂^•― and ^•NO, and two chalcones scavenged H₂O₂ and ^•NO. The structure-activity relationship analysis showed the importance of the presence of hydroxy groups in specific positions of the B-ring, varying according to the studied reactive species. Overall, chalcones seem to be slightly more active than 2-styrylchromones.

Acknowledgments: The work was supported through the project UIDB/50006/2020, funded by FCT/MCTES through national funds, and from the European Union (FEDER funds through COMPETE POCI-01-0145-FEDER-029253). Mariana Lucas thanks FCT for her PhD grant (2021.06746.BD). Marisa Freitas acknowledges her contract under the CEEC Individual (2020.04126.CEECIND/CP1596/CT0006).