Biography
Biography: Wilfried Dimpfel
Abstract
A “reverse pharmacology” approach was started with an extract of Sceletium tortuosum, currently sold as Zembrin® in
the USA, Canada, Brazil, Malaysia, and South Africa. It is a proprietary extract of a low-alkaloid cultivated selection of
Sceletium tortuosum, and is used by healthy people for enhancing mood, decreasing anxiety and stress and improving cognitive
function under stressful situations. As test model the hippocampus slice in vitro was chosen to compare its effects with four of its
alkaloid constituents, namely Mesembrine, Mesembrenone, Mesembrenol and Mesembranol. Measurement of the amplitude
of population spikes was performed in the presence of single shock stimulation and theta burst stimulation resulting in long
term potentiation (LTP). Rats were treated daily for one week with 5 or 10 mg/kg of Zembrin® before the hippocampus was
taken out for in vitro analysis. Amplitudes of the population spikes were dose dependently attenuated. Out of four glutamate
receptor agonists only Fluorowillardine was completely unable to induce its agonistic action. This points to an AMPA receptor
mediated attenuation of hippocampal excitability produced by repetitive dosing of Zembrin®. Superfusing the slices directly
with the alkaloids at nanomolar concentrations (3.5 – 35 nM) resulted in a concentration dependent attenuation of population
spike amplitudes. However, only Mesembrenol and Mesembranol were able to prevent the action of Fluorowillardine, thus
resembling the effect of the whole extract. Comparing now the chemical formula of the alkaloids in terms of a structure activity
relationship, the hydroxy group at C6 instead of a carbonyl group in mesembranol seems to be essential for interaction with
AMPA dependent transmission. Since attenuation of AMPA mediated transmission has been related to successful adjunctive
treatment of epileptic patients, Mesembranol - following the principle and methodology of “reverse pharmacology” - might
serve as chemical lead for the development of new drugs for the treatment of epilepsy.