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DOI: 10.1055/s-2007-993761
© Georg Thieme Verlag KG Stuttgart · New York
Modulation of GABAA Receptors by Valerian Extracts is Related to the Content of Valerenic Acid
Publication History
Received: June 20, 2007
Revised: October 30, 2007
Accepted: November 2, 2007
Publication Date:
19 December 2007 (online)
![](https://www.thieme-connect.de/media/plantamedica/200801/lookinside/thumbnails/10.1055-s-2007-993761-1.jpg)
Abstract
Valeriana officinalis L. is a traditionally used sleep remedy, however, the mechanism of action and the substances responsible for its sedative and sleep-enhancing properties are not fully understood. As we previously identified valerenic acid as a subunit-specific allosteric modulator of GABAA receptors, we now investigated the relation between modulation of GABAA receptors by Valerian extracts of different polarity and the content of sesquiterpenic acids (valerenic acid, acetoxyvalerenic acid). All extracts were analysed by HPLC concerning the content of sesquiterpenic acids. GABAA receptors composed of α1, β2 and γ2S subunits were expressed in Xenopus laevis oocytes and the modulation of chloride currents through GABAA receptors (IGABA) by Valerian extracts was investigated using the two-microelectrode voltage clamp technique. Apolar extracts induced a significant enhancement of IGABA, whereas polar extracts showed no effect. These results were confirmed by fractionating a highly active ethyl acetate extract: again fractions with high contents of valerenic acid exhibited strong receptor activation. In addition, removal of sesquiterpenic acids from the ethyl acetate extract led to a loss of IGABA enhancement. In conclusion, our data show that the extent of GABAA receptor modulation by Valerian extracts is related to the content of valerenic acid.
Abbreviations
AVA:acetoxyvalerenic acid
CNS:central nervous system
EA:crude ethyl acetate extract
EtOAc:ethyl acetate extract
GABA:γ-amino butyric acid
GABAA receptor:GABA activated type A receptor
H2O:distilled water extract
HVA:hydroxyvalerenic acid
IGABA:GABA-induced chloride current through GABAA receptors
MeOH:methanol extract
PE:petroleum ether extract
RV:reservoir volumina
TLC:thin layer chroamtography
VA:valerenic acid
VLC:vacuum liquid chromatography
Key words
Valeriana officinalis - Valerianaceae - GABAA-modulation - valerenic acid
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Prof. Brigitte Kopp
Department of Pharmacognosy
University of Vienna
Althansstrasse 14
1090 Wien
Austria
Phone: +43-1-4277-55255
Fax: +43-1-4277-55256
Email: Brigitte.kopp@univie.ac.at