The study on structure-activity relationship between chromone derivatives and inhibition of superoxide anion generating from human neutrophils

Over activation of neutrophils has been linked to many inflammatory diseases; one of critical pathologic mechanisms is that generation and exocellular release of superoxide anion from neutrophils results in peripheral tissues damage. Besides, in this study, 2-(3,5-dimethoxyphenoxy)-5,7-dimethoxy-chromen-4-one (4), a 2-phexnoychromone from our compound bank, was demonstrated to have the moderate inhibitory effect on superoxide anion generating. Therefore, serial chromones substituted with phenols or 3-flourothiophenol were designed, synthesized, and examined for suppression of superoxide anion generation. In accordance with the results, the methoxy group at 7 position (R³) of the chromone, as well as a hydrogen bond donor at a meta site of the phenyl ring greatly impacted on the activity. 2-(3-fluorophenyl)sulfanyl-7-methoxy-chromen-4-one (16), a successful example of bioisosteres from a phenol to a thiophenol, exhibited prominent anti-inflammatory effects with the IC₅₀ value against superoxide anion generation of 5.0 ± 1.4 μM.