Interaction between quercetin and Ca2+-calmodulin complex: possible mechanism for anti-tumor-promoting action of the flavonoid.

Quercetin was found to have similar inhibitory effects on tumor promoter-induced phenomena to those of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist. Moreover, quercetin was shown to interact directly with the Ca2+-calmodulin complex. These results suggest that quercetin may act as a calmodulin antagonist, and that its antagonistic effect on calmodulin may be important in its anti-tumor-promoting action in vivo.