APIGENIN, A COMPONENT OF MATRICARIA-RECUTITA FLOWERS, IS A CENTRAL BENZODIAZEPINE RECEPTORS-LIGAND WITH ANXIOLYTIC EFFECTS

The dried flower heads of Matricaria recutita L. (Asteraceae) are used in folk medicine to prepare a spasmolytic and sedative tea, Our fract ionation of the aqueous extract of this plant led to the detection of several fractions with significant affinity for the central benzodiaze pine receptor and to the isolation and identification of 5,7,4'-trihyd roxyflavone (apigenin) in one of them, Apigenin competitively inhibite d the binding of flunitrazepam with a K-i of 4 mu M and had no effect on muscarinic receptors, alpha(1)-adrenoceptors, and on the binding of muscimol to GABA(A) receptors. Apigenin had a clear anxiolytic activi ty in mice in the elevated plus-maze without evidencing sedation or mu scle relaxant effects at doses similar to those used for classical ben zodiazepines and no anticonvulsant action was detected. However, a 10- fold increase in dosage produced a mild sedative effect since a 26% re duction in ambulatory locomotor activity and a 35% decrement in hole-b oard parameters were evident. The results reported in this paper demon strate that apigenin is a ligand for the central benzodiazepine recept ors exerting anxiolytic and slight sedative effects but not being anti convulsant or myorelaxant.