Sceletium tortuosum is a succulent plant commonly found in South Africa, which is also known as Kanna. The pharmacological actions of a standardized extract of the plant have been reported to be dual PDE4 inhibition and 5-HT reuptake inhibition.
The mechanisms of action on the central nervous system (CNS) of a standardized extract were recently identified as comprising blockade of the serotonin (5-HT) transporter and selective inhibition of the phosphodiesterase-4 (PDE4) enzyme. 5-HT reuptake inhibitors (SSRIs) are widely used for the treatment of anxiety disorders and depression.