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Planta Med 2019; 85(11/12): 925-933
DOI: 10.1055/a-0921-7602
Biological and Pharmacological Activities
Original Papers
Georg Thieme Verlag KG Stuttgart · New York

A FLIPR Assay for Discovery of GABAA Receptor Modulators of Natural Origin[*]

Maria Teresa Faleschini
1   Pharmaceutical Biology, Pharmacenter, University of Basel, Basel, Switzerland
,
Anne Maier
2   Institute for Pharma Technology, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
,
Sarah Fankhauser
2   Institute for Pharma Technology, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
,
Katharina Thasis
2   Institute for Pharma Technology, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
,
Simon Hebeisen
3   BʼSys GmbH, Witterswil, Switzerland
,
Matthias Hamburger
1   Pharmaceutical Biology, Pharmacenter, University of Basel, Basel, Switzerland
,
Veronika Butterweck
2   Institute for Pharma Technology, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz, Switzerland
4   Zeller Medical AG, Romanshorn, Switzerland
› Author Affiliations
Further Information

Publication History

received 04 March 2019
revised 09 May 2019

accepted 10 May 2019

Publication Date:
24 May 2019 (online)

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Abstract

A fluorometric imaging plate reader (FLIPR) assay utilizing Chinese hamster ovary (CHO) cells stably transfected with GABAA receptors of α 1 β 2 γ 2 subunit composition was evaluated and validated for rapid screening of plant extract libraries and efficient localization of active compounds in extracts. Validation was performed with pure compounds and extracts known to contain allosteric GABAA receptor modulators. Plants extracts that had been previously reported as active in an assay using Xenopus laevis oocytes transiently expressing GABAA receptors of α 1 β 2 γ 2 subunit composition were also active in the FLIPR assay. A protocol for HPLC-based activity profiling was developed, whereby separations of 0.4 – 1.2 mg of extracts on an analytical HPLC column were found to be sufficient for the sensitivity of the bioassay. The protocol successfully localized the activity of known GABAergic natural products, such as magnolol in Magnolia officinalis, valerenic acid in Valeriana officinalis, and piperine in Piper nigrum extract. EC50 values of compounds (magnolol: 4.81 ± 1.0 µM, valerenic acid: 12.56 ± 1.2 µM, and piperine: 5.76 ± 0.7 µM) were found to be comparable or lower than those reported using Xenopus oocyte assays.

Key words

FLIPR - magnolol - valerenic acid - piperine - diazepam - GABAA

* Dedicated to Professor Dr. Cosimo Pizzaʼs 70th birthday in recognition of his outstanding contribution to natural product research.


Supporting Information

    Fluorescence readout in the FLIPR assay over 500 s for the controls, concentration-response curves for GABA and diazepam, and settings of the FlexStation used in this study are available as Supporting Information.

  • Supporting Information
 

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