title: In vitro characterization of transport and metabolism of the alkaloids: vincamine, vinpocetine and eburnamonine.
abstract: OBJECTIVE
  Vincamine, vinpocetine and eburnamonine are alkaloids known for their neuroprotective attributes, enhancement of cerebrovascular blood flow and antitumor effect of their derivatives. However, the relative metabolic stability of these alkaloids and their extrusion by the drug efflux transporters expressed at the blood-brain barrier (BBB) are not clear. In this study, we developed rapid and sensitive methods for the detection of these alkaloids and investigated their relative metabolic stability and their interaction with drug efflux transporters.
  
  
  METHODS
  UPLC methods were developed to analyze metabolic in vitro samples. Intrinsic clearance was determined using rat liver microsomal enzymes. Drug-stimulated transporter activity was estimated by measuring inorganic phosphate released from ATP spectrophotometrically.
  
  
  RESULTS
  The UPLC methods quantification level ranged from 0.02 to 0.025 µg/mL, indicating high sensitivity. The intrinsic clearance of eburnamonine was significantly less than both vincamine and vinpocetine. Different concentrations of the three drugs (4, 20 and 100 µM) induced minimal stimulation of the ATPase activity of the Bcrp and Pgp membrane transporters.
  
  
  CONCLUSIONS
  The developed simple, sensitive and reliable UPLC analysis methods can be utilized in future in vitro and in vivo studies. The three alkaloids demonstrated minimal interaction with the drug efflux transporters Pgp and Bcrp, concordant with the ability of these alkaloids to cross the BBB. The relative metabolic stability of eburnamonine compared to the other alkaloids suggests the use of eburnamonine or its derivatives as lead compounds for the development of antitumor and nootropic agents that need to cross the BBB and produce their pharmacological effects in the CNS.
authors.affiliation: Department of Pharmaceutical Sciences, Albany College of Pharmacy, Colchester, VT, USA.
authors.forename: Tamer E
authors.initials: TE
authors.lastname: Fandy
authors.affiliation: Pharmacokinetics and Biopharmaceutics Laboratory, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 N Pine Street, Room: N525 (Office), Baltimore, MD, 21201, USA.|Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Misr International University, Cairo, Egypt.
authors.forename: Inas
authors.initials: I
authors.lastname: Abdallah
authors.affiliation: Department of Pharmaceutical Chemistry, College of Pharmacy, King Abdulaziz University, Jeddah, KSA.
authors.forename: Maan
authors.initials: M
authors.lastname: Khayat
authors.affiliation: Department of BioMolecular Science, University of Mississippi, University, MS, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Colby
authors.affiliation: Pharmacokinetics and Biopharmaceutics Laboratory, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, 20 N Pine Street, Room: N525 (Office), Baltimore, MD, 21201, USA. hhassan@rx.umaryland.edu.|Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Helwan University, Cairo, Egypt. hhassan@rx.umaryland.edu.
authors.forename: Hazem E
authors.initials: HE
authors.lastname: Hassan
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004355:Drug Stability; D026901:Membrane Transport Proteins / Q000378:metabolism; D008862:Microsomes, Liver / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D015203:Reproducibility of Results; D014748:Vinca Alkaloids / Q000378:metabolism / Q000494:pharmacology; D014749:Vincamine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D026901:Membrane Transport Proteins; D018696:Neuroprotective Agents; D014748:Vinca Alkaloids; C013983:vinpocetine; D014749:Vincamine; C016422:eburnamonine
keywords: Alkaloids; Blood–brain barrier; Drug efflux transporters; Rat liver microsomes