Elsevier

Biochemical Pharmacology

Volume 59, Issue 11, 1 June 2000, Pages 1387-1394
Biochemical Pharmacology

Neuroscience
Pharmacological profile of apigenin, a flavonoid isolated from Matricaria chamomilla

https://doi.org/10.1016/S0006-2952(00)00264-1Get rights and content

Abstract

Dried flowers of Matricaria chamomilla L. are largely used to provide sedative as well as spasmolytic effects. In the present study, we examined in particular the pharmacological property of a fraction isolated from a methanolic extract of M. chamomilla, which was identified by HPLC–MS–MS analysis as apigenin. By radioreceptor binding assays, we demonstrated the ability of the flavone to displace a specific radioligand, [3H]Ro 15-1788, from the central benzodiazepine binding site. Electrophysiological studies performed on cultured cerebellar granule cells showed that apigenin reduced GABA (gamma-aminobutyric acid)-activated Cl currents in a dose-dependent fashion. The effect was blocked by co-application of Ro 15-1788, a specific benzodiazepine receptor antagonist. Accordingly, apigenin reduced the latency in the onset of picrotoxin-induced convulsions. Moreover, apigenin injected i.p. in rats reduced locomotor activity, but did not demonstrate anxiolytic, myorelaxant, or anticonvulsant activities. The present results seem to suggest that the inhibitory activity of apigenin on locomotor behaviour in rats cannot be ascribed to an interaction with GABAA–benzodiazepine receptor but to other neurotransmission systems, since it is not blocked by Ro 15-1788.

Section snippets

Extraction and HPLC analysis

Twenty grams of dried flower head powder of M. chamomilla L. (Grosserbe) was suspended in 200 mL of methanol for 24 hr. The suspension, after filtration, was evaporated under vac- uum. The residue was analysed by reverse-phase HPLC separation. The residue was reconstituted with 80% water/0.1% trifluoroacetic acid and 20% acetonitrile and chromatographed at 0.8 mL/min on a LiChrospher 100 RP-18 column (240 × 4.0 mm; 5 μM; Merck) equilibrated with 80% water/0.1% trifluoroacetic acid and 20%

Isolation of apigenin and binding experiments

HPLC analysis of the methanol extract of M. chamomilla revealed the presence of several compounds able to bind central benzodiazepine receptors which are still under identification procedure. One of the compounds was identified by HPLC–ESI–MS/MS analysis as apigenin, as determined by comparing the spectra shown in Fig. 1 with those of synthetic apigenin. The inhibition curve of apigenin reported in Fig. 2 showed the ability of apigenin to inhibit [3H]Ro 15-1788 specific binding to rat

Discussion

In traditional medicine, the dried flower heads of M. chamomilla are widely used to obtain sedative, spasmolytic, and anti-inflammatory effects. Furthermore, a depressive activity of a lyophilised infusion of flowers of M. chamomilla on the central nervous system was demonstrated in mice by Della Loggia et al. [20]. Many studies have been performed with the aim of clarifying which component is responsible for the sedative effect. Viola et al. [10] demonstrated that M. chamomilla contains

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