Planta Med 2008; 74 - L14
DOI: 10.1055/s-0028-1083859

HPLC-based profiling for natural products leads – GABAA receptor modulators and PI3 kinase inhibitors

M Hamburger 1
  • 1Department of Pharmaceutical Sciences, Institute of Pharmaceutical Biology, University of Basel, CH-4056 Basel, Switzerland

We have recently implemented a technology platform for a miniaturized activity-based approach in natural products discovery. The platform includes 2D-barcoded liquid extract libraries, HPLC-based micro-fractionation for bioactivity and simultaneous on-line spectroscopy (PDA, TOFMS, and MS/MS), and off-line NMR spectroscopy with a 1mm microprobe. This platform is generally applicable with mechanism-based and functional assays in the 96-well MTP format [1] and serves as a turntable for collaborative projects in various therapeutic areas.

γ-Aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the mammalian brain, and subunit-selective GABAA receptor agonists would have important therapeutic applications. The issue of sound validation and dereplication of profiling protocols will be discussed with a functional assay for GABAA receptor modulators using an automated two-microelectrode voltage-clamp assay with Xenopus oocytes expressing GABAA receptors of desired subunit composition [2]. Identification of GABAA receptor ligands with scaffolds new for the target will be presented, such as Diels-Alder adducts from Morus alba.

Aberrant phosphatidylinositol 3-kinase (PI3K) activity has been linked to the formation of cancer chronic inflammation and other diseases. We are screening for PI3K class III inhibitors using a mutated yeast for Vps43p. A library of >700 plant and fungal extracts for inhibitors provided very few hits, among these, a lipophilic extract from Citrus medica var. sarcodactylis pericarp. HPLC-based activity profiling of the extract, and cell-culture-based confirmatory testing of compounds will be described.

In a co-operation with the Swiss Tropical Institute, we screen for compounds active against malaria, leishmaniasis and trypanosomiasis. The validation of our profiling approach, and compounds identified from TCM plants will be discussed.

Acknowledgements: Swiss National Science Foundation, Steinegg Foundation, Freiwillige Akademische Gesellschaft.

References: 1. Potterat, O., Hamburger, M. (2006) Curr Org Chem 10:899–920, 2. Kim, HJ. et al. (2008) Planta Med 74: in press