Syrian rue or harmal (Peganum harmala) is a perennial succulent shrub with narrow, pinnately cut leaves and white solitary flowers, growing up to 1 meter but usually not more than 30 cm high, native from the Mediterranean to central and soutwest Asia. Its small angular brown seeds are traditionally used in dye making and for medicinal purposes in the Middle East. Peganum harmala is one of the plants speculated to be the Soma or Haoma of ancient Persia.

The seeds of Peganum harmala contain beta-carboline harmala alkaloids, primarily harmine and harmaline, which are both psychoactive and potent short-acting reversible inhibitors of MAO-A. The seeds also contain uterotonic alkaloids, which should be avoided by pregnant women (Ott 1996; Shulgin 1997; Mahmoudian 2002). In addition, the seeds have been shown to have both analgesic and antibacterial properties (Prashanth 1999).

In western culture Peganum harmala seeds are sometimes used as an MAOI in combination with other psychoactive substances, and less commonly as a psychoactive in their own right (Ott 1994; Shulgin, 1997). At psychoactive dosages, Peganum harmala typically produces heavy somatic effects (cf. Ott 1996, Shulgin 1997). Simple acid extractions are often used to isolate the harmala alkaloids. Due to its MAOI properties, it may be advisable to avoid certain foods in combination with Peganum harmala.