title: Intestinal absorption mechanisms of prenylated flavonoids present in the heat-processed Epimedium koreanum Nakai (Yin Yanghuo).
abstract: OBJECTIVE
  The purpose is to determine absorption mechanism of five bioactive prenylated flavonoids (baohuoside I, icariin, epimedine A, B, and C) present in heat-processed Epimedium koreanum Nakai (Yin Yanghuo).
  
  
  METHODS
  Transport of five prenylated flavonoids present in heat-processed herbs were studied in the human intestinal Caco-2 model and the perfused rat intestinal model.
  
  
  RESULTS
  In the perfused rat intestinal model, prenylated flavonoids with a monoglucosidic bond (e.g., icariin) was rapidly hydrolyzed into corresponding metabolites (e.g., baohuoside I). In the Caco-2 model, apical to basolateral permeability of a monoglycoside baohuoside I (1.46 x 10(-6) cm/sec) was more than 2 folds greater than four prenylated flavonoids with 2 or more sugar moieties (<0.6 x 10(-6) cm/sec). The slow apical to basolateral transport of baohuoside I was the result of efflux. This efflux was carrier-mediated and active since its transport was vectorial, concentration- and temperature-dependent with activation energies greater than 15 kcal/mol. Efflux of baohuoside I was significantly suppressed by inhibitors of BCRP and MRP2, whereas efflux of icariin was significantly inhibited only by p-glycoprotein inhibitor verapamil. Because YHH is often heat-processed for better efficacy, we determined and found the optimal condition for increasing contents of more bioavailable flavonoids (i.e., baohuoside I) to be 160-170 degrees C for 5-7 min.
  
  
  CONCLUSIONS
  Poor bioavailability of prenylated flavonoids results from their poor intrinsic permeation and transporter-mediated efflux. Heat processing parameters may be optimized to preserve the herb's bioavailable flavonoids, which help retain and improve its efficacy during processing.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, 1441 Moursund Street, Houston, TX 77030, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.forename: Yan Hong
authors.initials: YH
authors.lastname: Zhao
authors.forename: Xiao Bin
authors.initials: XB
authors.lastname: Jia
authors.forename: Ming
authors.initials: M
authors.lastname: Hu
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001682:Biological Availability; D018938:Caco-2 Cells; D034181:Epimedium / Q000737:chemistry*; D005419:Flavonoids / Q000302:isolation & purification / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D006868:Hydrolysis; D007408:Intestinal Absorption / Q000187:drug effects; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010477:Perfusion; D010539:Permeability; D054876:Prenylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D005419:Flavonoids; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; C000715087:ABCC2 protein, human; C116614:ABCG2 protein, human; C529106:epimedin A; C106053:epimedin B; C106054:epimedin C; C060988:baohuoside I; C056599:icariin