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Evidence-Based Complementary and Alternative Medicine
Volume 2012 (2012), Article ID 802625, 8 pages
http://dx.doi.org/10.1155/2012/802625
Research Article

Bioassay-Guided Isolation of Neuroprotective Compounds from Uncaria rhynchophylla against Beta-Amyloid-Induced Neurotoxicity

1School of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong
2Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, Chicago IL 60607, USA

Received 27 March 2012; Accepted 12 May 2012

Academic Editor: Karl Wah-Keung Tsim

Copyright © 2012 Yan-Fang Xian et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Uncaria rhynchophylla is a component herb of many Chinese herbal formulae for the treatment of neurodegenerative diseases. Previous study in our laboratory has demonstrated that an ethanol extract of Uncaria rhynchophylla ameliorated cognitive deficits in a mouse model of Alzheimer’s disease induced by D-galactose. However, the active ingredients of Uncaria rhynchophylla responsible for the anti-Alzheimer’s disease activity have not been identified. This study aims to identify the active ingredients of Uncaria rhynchophylla by a bioassay-guided fractionation approach and explore the acting mechanism of these active ingredients by using a well-established cellular model of Alzheimer’s disease, beta-amyloid- (Aβ-) induced neurotoxicity in PC12 cells. The results showed that six alkaloids, namely, corynoxine, corynoxine B, corynoxeine, isorhynchophylline, isocorynoxeine, and rhynchophylline were isolated from the extract of Uncaria rhynchophylla. Among them, rhynchophylline and isorhynchophylline significantly decreased Aβ-induced cell death, intracellular calcium overloading, and tau protein hyperphosphorylation in PC12 cells. These results suggest that rhynchophylline and isorhynchophylline are the major active ingredients responsible for the protective action of Uncaria rhynchophylla against Aβ-induced neuronal toxicity, and their neuroprotective effect may be mediated, at least in part, by inhibiting intracellular calcium overloading and tau protein hyperphosphorylation.