Structure-activity relationship in the ability of flavonols to inhibit chemiluminescence

Fourteen flavonoids were evaluated for their ability to inhibit chemiluminescence, either of neutrophils that had been briefly exposed to both luminol and phorbol-myristate acetate or to an enzymatic system with H2O2, luminol and horseradish peroxidase. Using chemiluminescence as the quantitative parameter, it can be concluded that the hydroxyl group in position 3 of the flavonols is vital for their inhibitory effect, and that two hydroxyl groups on the phenyl ring are optimal for such an effect. It was also noted that the C2-C3 double bond is essential for the flavonols' anti-oxidative effect. It is suggested that the ability of flavonols to suppress chemiluminescence is reciprocally correlated with their lipophilicity.