title: Stereoselective conjugation, transport and bioactivity of s- and R-hesperetin enantiomers in vitro.
abstract: The flavanone hesperetin ((+/-)-4'-methoxy-3',5,7-trihydroxyflavanone) is the aglycone of hesperidin, which is the major flavonoid present in sweet oranges. Hesperetin contains a chiral C-atom and so can exist as an S- and R-enantiomer, however, in nature 2S-hesperidin and its S-hesperetin aglycone are predominant. The present study reports a chiral HPLC method to separate S- and R-hesperetin on an analytical and semipreparative scale. This allowed characterization of the stereoselective differences in metabolism and transport in the intestine and activity in a selected bioassay of the separated hesperetin enantiomers in in vitro model systems: (1) with human small intestinal fractions containing UDP-glucuronosyl transferases (UGTs) or sulfotransferases (SULTs); (2) with Caco-2 cell monolayers as a model for the intestinal transport barrier; (3) with mouse Hepa-1c1c7 cells transfected with human EpRE-controlled luciferase to test induction of EpRE-mediated gene expression. The results obtained indicate some significant differences in the metabolism and transport characteristics and bioactivity between S- and R-hesperetin, however, these differences are relatively small. This indicates that for these end points, including intestinal metabolism and transport and EpRE-mediated gene induction, experiments performed with racemic hesperetin may adequately reflect what can be expected for the naturally occurring S-enantiomer. This is an important finding since at present hesperetin is only commercially available as a racemic mixture, while it exists in nature mainly as an S-enantiomer.
authors.affiliation: Division of Toxicology, Wageningen University, Tuinlaan 5, PO Box 8000, 6703 HE Wageningen, The Netherlands. Walter.Brand@WUR.nl
authors.forename: Walter
authors.initials: W
authors.lastname: Brand
authors.forename: Jia
authors.initials: J
authors.lastname: Shao
authors.forename: Elisabeth F
authors.initials: EF
authors.lastname: Hoek-van den Hil
authors.forename: Kathelijn N
authors.initials: KN
authors.lastname: van Elk
authors.forename: Bert
authors.initials: B
authors.lastname: Spenkelink
authors.forename: Laura H J
authors.initials: LH
authors.lastname: de Haan
authors.forename: Maarit J
authors.initials: MJ
authors.lastname: Rein
authors.forename: Fabiola
authors.initials: F
authors.lastname: Dionisi
authors.forename: Gary
authors.initials: G
authors.lastname: Williamson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: van Bladeren
authors.forename: Ivonne M C M
authors.initials: IM
authors.lastname: Rietjens
mesh_terms: D000818:Animals; D001692:Biological Transport; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D032084:Citrus sinensis / Q000737:chemistry; D003600:Cytosol / Q000378:metabolism; D005638:Fruit / Q000737:chemistry; D015870:Gene Expression / Q000187:drug effects; D020719:Glucuronides / Q000378:metabolism; D006569:Hesperidin / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007421:Intestine, Small / Q000378:metabolism / Q000648:ultrastructure; D008114:Liver Neoplasms, Experimental; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013451:Sulfonic Acids / Q000378:metabolism; D014162:Transfection
chemical_list: D020719:Glucuronides; D013451:Sulfonic Acids; D006569:Hesperidin; C013015:hesperetin