Relationship between structure and antioxidative properties of some 3-formylchromone derivatives.

Flavonoids, which generally exhibit very good antioxidant properties, contain the chromone unity. The work elucidates the relation between chemical structure of chromones and their ability to scavenge DPPH radicals. The work deals with antioxidative properties of some hydroxy derivatives of 3-formylchromones (without substituent, 6-hydroxy-, 7-hydroxy-, 7,8-dihydroxy-). It was found that the last two derivatives scavenge DPPH radicals, whereas the first two ones do not. It was demonstrated that the presence and location of hydroxyl groups play a crucial role for antioxidative activity of 3-formylchromones. The scavenging of DPPH radicals runs through H(+) abstraction from hydroxyl groups of formylchromones. The DPPH scavenging by 3-formylchromones with hydroxyl group in the 7th position is connected with the formation of more stable form of anion than in the case of 6-hydroxy-3-formylchromone. Calculation heats of formations of studied formylchromone anions confirmed this fact. All studied 3-formylchromones did not scavenge HO( ) radicals, what supports H(+) abstraction mechanism of DPPH scavenging.