Effects of hydroxylation of flavonoids on affinities.

Class	Ring	Position	Example	Affinity	Inhibition
Flavone	A	5H→OH	7-OH flavone → chrysin	↓	↑
		6H→OH	Chrysin → baicalein	↑	↓
		7H→OH	Flavone → 7-OH flavone	↓	↑
			Baicalin → baicalein	↓	↑
	B	3′H→OH	Apigenin → luteolin	↑	↑
		4′H→OH	Chrysin → apigenin	↓	↑
	C	3H→OH	Chrysin → galangin	↑	↑
			Apigenin → kaempferol	↑	↓
			Luteolin → quercetin	↓	↑
Flavonol	A	5H→OH	Fisetin → quercetin	↓	↑
	B	3′H→OH	Kaempferol → quercetin	↑	↑
		4′H→OH	Galangin → kaempferol	↑	↑
		5′H→OH	Quercetin → myricetin	↓	↓
Isoflavone	A	5H→OH	Daidzein → genistein	↑	↓
			Formononetin → biochanin A	↓	↓
Flavanone	A	7H→OH	Naringin → naringenin	↓	↑