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 A₁, dopamine (transporter, D₁, D_2S, D₃, D_4.4 and D₅), serotonin (transporter, 5-HT_1A, 5-HT_1B, 5-HT_4e, 5-HT₆ and 5-HT₇) and the GABA benzodiazepine receptor.

Results

Interactions were demonstrated with the adenosine A₁ receptor, dopamine transporter and dopamine D₅ receptor (antagonist activity), serotonin receptors (5-HT_1B and 5-HT₆ antagonist activity) and the GABA benzodiazepine receptor at a concentration of 100 μg/ml or lower. ME had an affinity with adenosine A₁ (K_i of 9.2 ± 1.1 μg/ml) and potentiated the GABA activated chloride current at the benzodiazepine subunits of the GABA receptor (maximum effect at 50 μg/ml). ME had a modest antagonist action with 5-HT₆ and ZE with the 5-HT_1B 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.