On the Relationship between the Chemical Structure and the Cyclic AMP Phosphodiesterase Inhibitory Activity of Flavonoids as Studied by 13C NMR

The relationship between the chemical structure and the cyclic adenosine monophosphate phosphodiesterase inhibitory activity was studied regarding forty-eight flavones, thirty-five flavanones, and six isoflavones by using the 13C NMR chemical shift averaged over all aromatic carbons in a compound. The average value of potent 13C chemical shifts over the aromatic carbons active flavonoids (IC500.6–20.0×10-5M/L) are within the range from d 133.5 to d 135.7, but those of the inactive flavonoids and the weak active flavonoids are not within this range. This means that the averaged 13C chemical shift becomes an “index” for testing the inhibitory activity. Further, the above relationship was proposed as a means for conveniently determining the inhibitory activity.