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As part of our ongoing research into botanical therapies for anxiety disorders, the neotropical vine Souroubea sympetala was chosen for study as a phytochemical discovery strategy focusing on rare Central American plant families. When orally administered to male Sprague-Dawley rats, the crude plant extract, its ethyl acetate fraction, supercritical carbon dioxide fraction, or its isolated triterpenes reduced anxiety and/or fear-related behavior in standardized behavioral models. Pharmacological studies showed that the extracts acted at the benzodiazepine GABA receptor and reduced corticosterone levels. A preparation containing Souroubea fortified with a second triterpene containing plant, Platanus occidentalis, was shown to be safe in a 28-day feeding trial with beagles at 5 times the intended dose. Subsequent trials with beagles in a thunderstorm model of noise aversion showed that the material reduced anxiety behaviors and cortisol levels in dogs. The formulation has been released for the companion animal market in Canada and the USA under the Trademark "Zentrol." Ongoing research is exploring the use of the material in treatment of anxiety and post-traumatic stress in humans.

This ethnobotanical study in the spirit of transdisciplinarity, and in collaboration with Q'eqchi' Maya traditional healers, compares traditional Q'eqchi' Maya ecosystem constructs or environmental zones with scientific ecosystems. To determine which categorization method better accommodates Q'eqchi' Maya medicinal plant diversity, we analized 26 transects representing 160 medicinal plant occurrences. Our transect array encompasses a representative sampling of Q'eqchi' Maya medicinal plant repertoire with use values broadly distributed over 17 usage categories. With a cumulative frequency of 2,235 medicinal plants through ecological zones, we conducted one-way ANOVA on the mean number of medicinal plant species identified in transects of the two conceptual schemes being contested. Our analysis reveals the Q'eqchi Maya environmental zones are the most salient. That is, knowledge of the Q'eqchi' Maya environmental zones improves one's ability to predict whether there will be a high or low abundance of Q'eqchi' Maya medicinal plant species in a particular region, whereas knowledge of scientific ecosystems does not accomplish this feat as well. This is a notable finding as it suggests that if indeed Q'eqchi' Maya medicinal plant diversity is better accounted for by the zones as envisioned by the Q'eqchi' Maya, then it should be this mode of conceptualization that should be adopted by scientists and conservationists when trying to locate and protect regional Q'eqchi' Maya medicinal plant diversity. These efforts serve as a model internationally in the conservation of medicinal plant biodiversity supportive of culturally relative holistic health promotion.

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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 GABAA-benzodiazepine (GABAA-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 GABAA-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 GABAA-BZD receptor. An in vitro GABAA-BZD competitive receptor binding assay also demonstrated that S. sympetala extracts have an affinity for the GABAA-BZD receptor, with an EC50 value of 123 μg/mL (EtOAc leaf extract) and 154 μg/mL (supercritical CO2 extract). These experiments indicate that S. sympetala acts at the GABAA-BZD receptor to elicit anxiolysis.