Relationships between Structures of Hydroxyflavone Derivatives and their Anti-oxidative Activities

Primuletin, chrysin, and luteolin belong to hydroxyflavones. Although they have small differences in their hydroxyl groups, these make big differences in their biological activities. In order to elucidate relationships between structures of hydroxyflavones and their biological activities, we tested anti-oxidative effects of 20 hydroxyflavone derivatives belonged to flavonoids, which are well-known to possess anti- oxidative effects. 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay, one of experiments to screen anti-oxidative effects, was performed for biological activities of hydroxyflavone derivatives. Twenty commercially available hydroxyflavones were tested for their anti-oxidative effects. For structure- activity relationship calculations, comparative molecular field analysis (CoMPA) was carried out. Based on the CoMPA contour maps, electronegative substituents are favorable for high DPPH radical scavenging effect. It is well agreed with the results obtained from the CoMPA contour maps where electronegative substituents are favorable because ortho positioned hydroxyl groups can cause larger electronegativity than separated hydroxyl groups. For high DPPH radical scavenging effect, hydroxyflavones should contain ortho positioned hydroxyl groups in their structures.