Extracts of Aloysia citrodora Paláu (Lemon verbena) shows CNS activities by inhibition of neurotransmitter re-uptake in vitro

Lemon verbena, Aloysia citrodora Paláu (Verbenaceae) is worldwide used due to the flavor and medicinal properties of leaves and essential oil. The leaves are used traditionally in tea and according to HMPC monograph for relief of mild symptoms of mental stress and to aid sleep [1]. Market preparations are also aqueous dry extracts or hydroethanolic tinctures. However only the essential oil is described for CNS activities as neuroprotective [2]. For the traditional use of Lemon verbena leaves preparations with different ways of manufacturing no clear CNS indication exists.

The objective of the study was to analyze the effects of different extraction solvents on the pharmacological activities of Lemon verbena leaves extracts. We investigated the effects on serotonin, norepinephrine and dopamine re-uptake in rat synaptosomes in vitro (method acc. [3]). For extraction, the dried leaves of one batch were extracted by exhaustive percolation. The tested extraction solvents were purified water, EtOH 20% V/V, EtOH 50% V/V, and EtOH 96% V/V.

All extracts inhibited the re-uptake of the three neurotransmitters in a dose-dependent manner. The inhibition of norepinephrine and dopamine re-uptake was in general stronger than that of serotonin. The results confirmed the important influence of the extractant. The strongest inhibition was detected for a polar solvent (EtOH 20% V/V) followed by the most lipophilic extract resp. a middle-polar solvent (EtOH 96% V/V > 50% V/V >> water). For water as solvent, IC₅₀ values were higher by a factor of 3–8, which indicates an unexpected activity increase for hydroethanolic extracts compared to aqueous extracts.

The overall very good inhibition of the neurotransmitter re-uptake confirms the excellent potential of Lemon verbena leaves extracts and puts an application in mild depression, ADHD or mental impairment in future focus.

Publication History

Article published online:
14 June 2023

• References

• 1 EU herbal monograph on Aloysia citrodora Paláu (syn. Aloysia triphylla (L'Hér.) Kuntze; Verbena triphylla L'Hér.; Lippia citriodora Kunth), folium. EMA/HMPC/376770/2019
• 2 Bahramsoltani R. et al. J Ethnopharmacology 2018; 222: 34-51
• 3 Perovic S, Müller WE.. Arzneimittelforschung 1995; 45: 1145-1148