“ Papaverine (3 microM) added to the organ bath 15 min before … relaxing effect of the flavonoids and significantly decreased their IC50 ( genistein 20.2 +/- 2.0 vs. 9.8 +/- 1.4 microM; kaempferol 10.1 +/- 1.….7 microM; quercetin 13.2 +/- 1.2 vs. 7.8 +/- 1.4 microM).”