title: Experimental determination of octanol-water partition coefficients of quercetin and related flavonoids.
abstract: Octanol-water partition coefficient (log P) values were determined for flavonoids from the flavone, flavonol, flavanone, and isoflavonoid subclasses. Each flavonoid was dissolved in an octanol-water system and allowed to equilibrate, and then both fractions were analyzed by high-performance liquid chromatography. log P was calculated as log[ratio of the concentration in the octanol phase to the concentration in the aqueous phase at pH 7.4]. The aglycons were more lipophilic than any conjugate. The conjugate moiety had a more significant effect on log P than the aglycon moiety. Quercetin was the least lipophilic aglycon (log P = 1.82 +/- 0.32) and, together with kaempferol (log P = 3.11 +/-0.54), gave the most variable results. The isoflavones genistein and daidzein and the isoflavone metabolite equol gave relatively high log P values (3.04 +/- 0.02, 2.51 +/- 0.06, and 3.20 +/- 0.13, respectively), while glycitein had an unexpectedly low value of 1.97 +/- 0.05. The conjugation characteristics and hydroxylation pattern were the most important determinants of log P in general, and log P was highly variable within the flavonoid subclass. The results are discussed in terms of further understanding of the in vivo fate of the flavonoids as important dietary bioactives.
authors.affiliation: Procter Department of Food Science, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Rothwell
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Day
authors.forename: Michael R A
authors.initials: MR
authors.lastname: Morgan
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005419:Flavonoids / Q000737:chemistry*; D000442:Octanols / Q000737:chemistry*; D011794:Quercetin / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D000442:Octanols; D014867:Water; D011794:Quercetin