Interactions of Magnolia and Ziziphus extracts with selected central nervous system receptors

Ethnopharmacological relevance: Magnolia officinalis Rehder and Wilson [Magnoliaceae] bark and Ziziphus spinosa (Buhge) Hu ex. Chen. [Fam. Rhamnaceae] seed have a history of use in traditional Asian medicine for mild anxiety, nervousness and sleep-related problems. Aim of the study: To identify pharmacological targets, extracts of Magnolia officinalis (ME), Ziziphus spinosa (ZE), and a proprietary fixed combination (MZE) were tested for affinity with central nervous system receptors associated with relaxation and sleep. Methods: In vitro radioligand binding and cellular functional assays were conducted on: adenosine A,, dopamine (transporter, D-1, D-2S, D-3, D-4.4 and D-5), serotonin (transporter, 5-HT1A, 5-HT1B, 5-HT4e, 5-HT6 and 5-HT7) and the GABA benzodiazepine receptor. Results: Interactions were demonstrated with the adenosine A(1) receptor, dopamine transporter and dopamine D-5 receptor (antagonist activity), serotonin receptors (5-HT1B and 5-HT6 antagonist activity) and the GABA benzodiazepine receptor at a concentration of 100 mu g/ml or lower. ME had an affinity with adenosine A(1) (K-i of 9.2 +/- 1.1 mu g/ml) and potentiated the GABA activated chloride current at the benzodiazepine subunits of the GABA receptor (maximum effect at 50 mu g/ml). ME had a modest antagonist action with 5-HT6 and ZE with the 5-HT1B receptor. Conclusion: The interactions in the receptor binding models are consistent with the traditional anxiolytic and sleep-inducing activities of Magnolia officinalis bark and Ziziphus spinosa seed. Published by Elsevier Ireland Ltd