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Changes in the intestinal absorption mechanism of icariin in the nanocavities of cyclodextrins

Authors Zhang Y, Wang, Cui Y, Meng F, Lin

Received 17 April 2012

Accepted for publication 14 June 2012

Published 2 August 2012 Volume 2012:7 Pages 4239—4249

DOI https://doi.org/10.2147/IJN.S33014

Review by Single-blind

Peer reviewer comments 2

Ye Zhang,1 Qiang-Song Wang,1 Yuan-Lu Cui,1 Fan-Cui Meng,2 Ke-Ming Lin1

1Tianjin State Key Laboratory of Modern Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, People's Republic of China; 2Tianjin Key Laboratory of Molecular Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin, People's Republic of China

Abstract: Icariin is a bioactive herbal ingredient isolated from Herba epimedii, which has been widely used for the treatment of osteoporosis and male sexual dysfunction in traditional Chinese medicine. The major objective of this work is to investigate the different enhancing effects of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) on the intestinal absorption of icariin, and to identify the molecular mechanisms of this action. Host–guest-type interactions of icariin with cyclodextrins nanocavities were unambiguously demonstrated by the phase-solubility diagram, ultraviolet spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray powder diffractometry, and two dimensional proton nuclear magnetic resonance rotating-frame Overhauser effect spectroscopy. These results were further supported using molecular modeling studies. The rat single-pass intestinal perfusion model showed that the absorption of icariin was affected by P-glycoprotein (Pgp). The icariin/HP-β-CD inclusion complex provided greater enhancement in the intestinal absorption than the icariin/β-CD inclusion complex. Therefore, the enhancing effect was involved in a solubilizing effect and/or Pgp inhibitory effect. Finally, fluorescence anisotropy measurements and Pgp adenosine triphosphatase (ATPase) assay demonstrated that β-CD exhibited no effect on Pgp, while HP-β-CD showed inhibition by restraining the Pgp ATPase activity rather than changing the fluidity of cell membrane.

Keywords: icariin, cyclodextrin, inclusion complex, molecular modeling, P-glycoprotein (Pgp), intestinal absorption

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