Effects of Hydroxy and Methoxy Substituents on NMR Data in Flavonols
Eunjung Lee · Bulletin of the Korean Chemical Society · 2008
Kaempferide, kaempferol, and galangin belong to flavonol, one of flavonoid classes.Even they have the same moiety as flavonol, their binding affinities for a hexahistidine-tagged C-terminal nucleotide-binding domain are different with each other.1The dissociation constants of flavonol, kaempferide, kaempferol, and galangin are 10.1, 4.5, 6.7, and 5.3 mM, respectively.Galangin contains two more hydroxyl groups than flavonol, and kaempferol has three more hydroxyl groups.Kaempferide differs with kaempferol in only one substituent: 4'-hydroxyl group of kaempferol is switched to 4'-methoxyl group in kaempferide.Likewise, galangin and kaempferide show different enzymatic kinetic parameters, Vmax/Kn, for cytochrome P450 isomers CYP2C9 and CYP1A1 which take an important role in oxidative metabolism of galangin and kaempferide.The values of Vmax/Km of galangin for CYP2C9 and CYP1A1 were 59.0 and 10.2 ^L/min/mg, respectively, and those of kaempferide were 5.1 and 1.9, respectively.2While kaempferide has 4'methoxyl group, galangin does not have it.As a result, it can be considered that the substitution of hydroxyl or/and methoxyl groups on flavonols results in significant changes of the biological activities.Flavonol derivatives are being