DIET/NUTRIENT INTERACTIONS WITH DRUG TRANSPORTERS - Drug Transporters: Molecular Characterization and Role in Drug Disposition - page 679

TABLE 22.2. Chemical Structures of Subclasses of Flavonoids

Substitutions a

Structural Representative

Formula Flavonoids 5 7 2 3 4 5

Flavones

3'

Apigenin OH OH H H OH H

4'

2'

Chrysin OH OH H H H H

5'

O

7

Luteolin OH OH H OH OH H

6

Diosmetin OH OH H OH O-Me H

5

O

Flavonols

Fisetin H OH H OH OH H

Galangin OH OH H H H H

Kaempferol OH OH H H OH H

O

Morin OH OH OH H OH H

OH

Myricetin OH OH H OH OH OH

O

Quercetin OH OH H OH OH H

Flavanones

Hesperitin OH OH H OH O-Me H

O

Naringenin OH OH H H OH H

O

Flavanols

Epicatechin OH OH H OH OH H

O

Epigallocatechin OH OH H OH OH OH

OH

Flavanolols

O

Silibinin OH OH H H Selane H

OH

O

Isoflavones
O

Biochanin A OH OH H H O-Me H

Genistein OH OH H H OH H

Daidzein H OH H H OH H

O

a O-Me, methoxy.

recently, in Pgp-overexpressing KB-C2 carcinoma cells, quercetin and kaempferol
significantly inhibited Pgp activity and increased cellular accumulation of rhodamine
123 and daunorubicin. 152 The reason(s) for these observed disparate results is still
unclear. One possible explanation might be the existence of multiple drug-binding
sites on Pgp and various allosteric effects of flavonoids on these sites. It has been
shown that quercetin could preferentially bind to the Hoechst 33342-binding site on
Pgp and inhibited Hoechst 33342 transport, presumably via competitive inhibition. In
contrast, binding of quercetin to the Hoechst 33342 site resulted in increased binding