Clerodane Diterpenes from as Allosteric GABA Receptor Modulators.

J Nat Prod

Pharmaceutical Biology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland.

Published: May 2022

An EtOAc extract of leaves led to an allosteric potentiation of the GABA signal in a fluorometric imaging plate reader (FLIPR) assay on Chinese hamster ovary (CHO) cells stably expressing GABA receptors with an αβγ subunit composition. The activity was tracked by HPLC-based activity profiling, and four known (, , , and ) and five new clerodane-type diterpenoids (, -, and ) were isolated. Compounds - were obtained from the active time window. The absolute configuration of all compounds was established by ECD. Compounds , , and exhibited EC values of 0.5, 4.6, and 1.4 μM, respectively. To explore possible binding sites at the receptor, the most abundant diterpenoid was tested in combination with diazepam, etazolate, and allopregnanolone. An additive potentiation of the GABA signal was observed with these compounds, while the effect of was not inhibited by flumazenil, a negative allosteric modulator at the benzodiazepine binding site. Finally, the activity was validated in voltage clamp studies on oocytes transiently expressing GABA receptors of the αβγS and αβ subtypes. Compound potentiated GABA-induced currents with both receptor subunit compositions [EC (αβγS) = 43.6 μM; = 809% and EC (αβ) = 57.6 μM; = 534%]. The positive modulation of GABA-induced currents was not inhibited by flumazenil, thereby confirming an allosteric modulation independent of the benzodiazepine binding site.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9150179PMC
http://dx.doi.org/10.1021/acs.jnatprod.1c00840DOI Listing

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