Kanna (Sceletium tortuosum) is a succulent plant from South Africa primarily used as a mood stabilizer. It acts on serotonin, which makes it useful for managing depression, anxiety, and low libido.

Phosphodiesterase 4 (PDE4) is an enzyme that breaks down cyclic adenosine monophosphate (cAMP), a molecule involved in a wide range of processes including brain function. Similar to other PDE4 inhibitors, kanna seems to reduce the activity of this enzyme, an effect that may help with depression, anxiety, and other mental issues.

Clinical studies have determined that the three main alkaloids of kanna: mesembrine, mesembrenone, and mesembrenol are serotonin reuptake inhibitors, which could produce anti-depression effects. A recent 2022 animal study compared Zembrin® and escitalopram, a common anti-depressant medication.