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

Ethnopharmacological relevanceMagnolia 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 studyTo 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.MethodsIn vitro radioligand binding and cellular functional assays were conducted on: adenosine A1, dopamine (transporter, D1, D2S, D3, D4.4 and D5), serotonin (transporter, 5-HT1A, 5-HT1B, 5-HT4e, 5-HT6 and 5-HT7) and the GABA benzodiazepine receptor.ResultsInteractions were demonstrated with the adenosine A1 receptor, dopamine transporter and dopamine D5 receptor (antagonist activity), serotonin receptors (5-HT1B 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 (Ki 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-HT1B receptor.ConclusionThe interactions in the receptor binding models are consistent with the traditional anxiolytic and sleep-inducing activities of Magnolia officinalis bark and Ziziphus spinosa seed.