Wikipedia
Mesembrenone
Mesembrenone is an alkaloid constituent of Sceletium tortuosum (Kanna). Similar to modern synthetic antidepressants, it is a potent (IC < 1 μM) selective inhibitor of the serotonin transporter (SERT) (that is, a selective serotonin reuptake inhibitor; K = 27 nM) and also a phosphodiesterase 4 (PDE4) inhibitor (K = 470 nM).