Investigation of the antagonism of the spasmogenic effect of three polypeptides by 12 flavonoids revealed that generally, the aglucones were more potent than the glycosides. Against angiotensin the order of potency was homoeriodictyol, quercetin, morin, rhamnetin, and 4‐methylesculetin; against bradykinin it was quercetin, rhamnetin, and homoeriodictyol; and against eledoisin it was quercitrin, morin, rhamnetin, and catechin. The other flavonoids showed varying degrees of activity but they tended to show less activity as their doses were increased. Structure‐activity evaluation revealed that the most active compounds had free phenolic hydroxyl groups in the 5.7‐positions of the γ‐benzopyrone nucleus. Other structural requirements were also discussed. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company
