Apigenin, a component of Matricaria recutita flowers, is a central benzodiazepine receptors-ligand with anxiolytic effects.
Level 5 - mechanism / opinion, no new human data
Preclinical bench (in vitro binding assay) and animal (mouse behavioral model) study.
PubMed 7617761 · doi:10.1055/s-2006-958058
What was done
Researchers fractionated aqueous extracts of Matricaria recutita (chamomile) flower heads to identify active constituents. In vitro competitive binding assays tested isolated apigenin (5,7,4'-trihydroxyflavone) against central benzodiazepine receptors (flunitrazepam binding), muscarinic receptors, alpha 1-adrenoceptors, and GABAA receptors (muscimol binding). In vivo behavioral assays in mice evaluated anxiolytic activity (elevated plus-maze), sedation (ambulatory locomotor activity and hole-board test), muscle relaxation, and anticonvulsant properties.
What was found
Apigenin competitively inhibited flunitrazepam binding with a Ki of 4 µM, while exhibiting no binding to muscarinic receptors, alpha 1-adrenoceptors, or muscimol-binding GABAA sites. In mice, apigenin demonstrated anxiolytic activity in the elevated plus-maze at doses comparable to classical benzodiazepines without producing muscle relaxation, sedation, or anticonvulsant effects. At a 10-fold higher dose, it induced mild sedation, demonstrated by a 26% reduction in ambulatory locomotor activity and a 35% decrement in hole-board parameters.
Why it matters
This study identifies apigenin as a key benzodiazepine-receptor ligand in chamomile that separates anxiolytic activity from muscle relaxation and motor sedation at baseline doses in rodents.
Limits
The study is restricted to in vitro and rodent models, providing no direct pharmacokinetic or efficacy data in humans. The abstract does not report the total number of mice tested, specific milligram-per-kilogram doses, exact baseline plus-maze metrics, variance measures, or p-values.
Cited by
- partial Apigenin and chamomile act to quiet or downregulate frontal cortex activity to facilitate sleep onset.