3-O-Methylquercetin (E6044-GRP)

3-O-Methylquercetin is a flavone isolated from Rhamnus nakaharai Hayata (Rhamnaceae), an inhibitor of cAMPand cGMP-phosphodiesterases(PDE) with an IC50 of 13.8 μM and 14.3 μM respectively. It also inhibits β-secretase with an IC50 of 6.5 μM. It exhibits antiviral activity and has been used in folk medicine for constipation, inflammation, tumors, and asthma.