title: Experimental and computational studies of epithelial transport of mefenamic acid ester prodrugs.
abstract: OBJECTIVE
  A series of ester derivatives of mefenamic acid were synthesized with the aim of suppressing local gastrointestinal toxicity of mefenamic acid. A computational method was used to assist the design of the prodrug and to gain insights into the structure relationship of these compounds as P-glycoprotein (P-gp) substrates. The prodrugs were studied for their enzymatic stability, bidirectional permeability across Caco-2 monolayer, and their potential as transporter modulators
  
  
  METHODS
  Bidirectional transport studies were performed using Caco-2 cells. Compounds exhibiting an efflux ratio of > or =2 were further examined for their potential interaction with P-gp and multidrug resistance-associated protein (MRP) using verapamil and indomethacin. Calcein efflux inhibition studies were conducted to investigate the efflux mechanism of these compounds. Geometry optimization of the esters was performed, and the spatial separation of two electron donor groups of each prodrug was measured.
  
  
  RESULTS
  Morpholinoethyl ester (3) and pyrrolidinoethyl ester (4) of mefenamic acid showed evidence of efflux mechanism. Inhibition by verapamil had a pronounced effect on the transport of 3 and 4. Indomethacin, however, completely inhibited the apical efflux of 3 but enhanced the efflux ratio of 4. Both compounds increased the ratio of cellular calcein accumulation by 3- to 5-fold over control. Consistent with the experimental data, the computational results suggest the involvement of P-gp or its interaction in 3 and 4 transport.
  
  
  CONCLUSIONS
  Apical efflux of 3 is associated with P-gp and MRP, but the efflux of 4 involves P-gp and/or MRP. The computational approach used in this study provided the basis for P-gp substrates of compounds 3 and 4 from their electron donor subunits spatial separation.
authors.affiliation: Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat-Yai, Songkhla, Thailand.
authors.forename: Kamonthip
authors.initials: K
authors.lastname: Wiwattanawongsa
authors.forename: Vimon
authors.initials: V
authors.lastname: Tantishaiyakul
authors.forename: Luelak
authors.initials: L
authors.lastname: Lomlim
authors.forename: Yon
authors.initials: Y
authors.lastname: Rojanasakul
authors.forename: Sirirat
authors.initials: S
authors.lastname: Pinsuwan
authors.forename: Sanae
authors.initials: S
authors.lastname: Keawnopparat
mesh_terms: D000818:Animals; D001702:Biopharmaceutics / Q000379:methods / Q000639:trends; D018938:Caco-2 Cells; D003198:Computer Simulation; D004795:Enzyme Stability / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005452:Fluoresceins / Q000378:metabolism; D006801:Humans; D008297:Male; D008528:Mefenamic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*; D011355:Prodrugs / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013678:Technology, Pharmaceutical / Q000379:methods / Q000639:trends*
chemical_list: D005452:Fluoresceins; D011355:Prodrugs; C085925:calcein AM; D008528:Mefenamic Acid