Souroubea sympetala (Marcgraviaceae): a medicinal plant that exerts anxiolysis through interaction with the GABA A benzodiazepine receptor

• Published in: Canadian journal of physiology and pharmacology 2014-09, Vol.92 (9), p.758-764
• Main Authors: Mullally, Martha, Cayer, Christian, Kramp, Kari, Otárola Rojas, Marco, Sanchez Vindas, Pablo, Garcia, Mario, Poveda Alvarez, Luis, Durst, Tony, Merali, Zul, Trudeau, Vance L., Arnason, John T.
• Format: Article
• Language: English
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/cjpp-2014-0213

The mode of action of the anxiolytic medicinal plant Souroubea sympetala was investigated to test the hypothesis that extracts and the active principle act at the pharmacologically important GABA A –benzodiazepine (GABA A –BZD) receptor. Leaf extracts prepared by ethyl acetate extraction or supercritical extraction, previously determined to have 5.54 mg/g and 6.78 mg/g of the active principle, betulinic acid, respectively, reduced behavioural parameters associated with anxiety in a rat model. When animals were pretreated with the GABA A –BZD receptor antagonist flumazenil, followed by the plant extracts, or a more soluble derivative of the active principle, the methyl ester of betulinic acid (MeBA), flumazenil eliminated the anxiety-reducing effect of plant extracts and MeBA, demonstrating that S. sympetala acts via an agonist action on the GABA A –BZD receptor. An in vitro GABA A –BZD competitive receptor binding assay also demonstrated that S. sympetala extracts have an affinity for the GABA A –BZD receptor, with an EC 50 value of 123 μg/mL (EtOAc leaf extract) and 154 μg/mL (supercritical CO 2 extract). These experiments indicate that S. sympetala acts at the GABA A –BZD receptor to elicit anxiolysis.