Affinity of Iresine herbstii and Brugmansia arborea extracts on different cerebral receptors

Iresine herbstii Hook. (Amaranthaceae) and Brugmansia arborea (L.) Lagerheim (Solanaceae) are used in the northern Peruvian Andes for magic-therapeutical purposes. The traditional healers use Iresine herbstii with the ritual aim to expel bad spirits from the body. Furthermore, Iresine herbstii was used in association with other plants, such as Trichocereus pachanoi Britt. et Rose, for divination, to diagnose diseases, and to take possession of another identity. Also, species of Brugmansia have been reported to be used during ritual practices for magical and curative purposes. Given the above evidence, the aim of the present study is to evaluate if the central effects of Iresine herbstii and Brugmansia arborea could be associated with interaction with SNC receptors. Two Iresine herbstii extracts (methanolic and aqueous) and one Brugmansia arborea aqueous extract were tested for in vitro affinity on 5-HT1A, 5-HT2A, 5-HT2C, D1, D2, α1, and α2 receptors by radioligand binding assays. The biological materials for binding assay (cerebral cortex) were taken from male Sprague–Dawley rats. The extracts affinity for receptors is definite as inhibition percentage of radioligand/receptor binding and measured as the radioactivity of remaining complex radioligand/receptor. The data obtained for Iresine extracts have shown a low affinity for the 5-HT1A receptor and no affinity for 5-HT2A receptor. Otherwise the methanolic extract showed affinity for 5-HT2C receptor (IC50: 34.78 μg/ml) and for D1 receptor (IC50: 19.63 μg/ml), instead the Iresine aqueous extract displayed a lower affinity for D1 (48.3% at the maximum concentration tested) and a higher value of affinity for D2 receptors (IC50: 32.08 μg/ml). The Brugmansia aqueous extract displayed affinity for D1 receptors (IC50: 17.68 μg/ml), D2 receptors (IC50: 15.95 μg/ml) and weak affinity for the serotoninergic receptors. None of the three extracts showed relevant affinity to the α1, and α2 receptors. The results of our experiments indicate that Iresine herbstii methanolic extract was able to interact with the central 5-HT2C and D1 receptors and Iresine herbstii aqueous extract showed affinity for D2 receptors, thus confirming their ritual use. Instead Brugmansia arborea was able to interact only with the central dopamine receptors tested. Parallel studies are currently in progress for evaluating the extracts affinity and active components towards these and other receptor types (GABAergic).