Tetrahydroharmine is also found in B. caapi and P. harmala. Dr. Alexander Shulgin has suggested that harmine may be a breakdown product of harmaline.[2] Harmine and harmaline are both a reversible inhibitor of monoamine oxidase A (RIMAs). They can stimulate the central nervous system by inhibiting the metabolism of monoamine compounds such as serotonin and norepinephrine.