Alkaloids from Boophone disticha with affinity to the serotonin transporter

Boophone disticha L. Herb (Amaryllidaceae) is used in traditional medicine for treatment of painful wounds, headaches, skin disorders, inflammatory conditions, rheumatic pains and anxiety. At least eight alkaloids have been characterized and reported in the literature. Of these buphanidrine and buphanamine have affinity to the serotonin transporter (SERT). Alkaloids from other Amaryllidaceae species have also shown affinity to SERT. In this study, an ethanol extract was prepared from dry bulbs. Through HPLC–UV separation five peaks were collected and characterized by LC-MS and 1H NMR and led to the identification of crinine, buphanamine, buphanidrine, distichamine and buphanisine. The activity of these compounds was tested in a binding assay using [3H]-citalopram as ligand and a functional SERT inhibition assay utilizing COS-7 cells expressing hSERT. The four active compounds, buphanamine, buphanidrine, buphanisine and distichamine, had IC50-values of 55 µM, 62 µM, 199 µM and 65 µM respectively, in the binding assay. The alkaloids also showed activity in the functional assay, buphanidrine and distichamine being the most active with IC50-values of 513 µM and 646 µM, respectively.