An indole alkaloid fundamental parent with a structure of 9H-beta-carboline carrying a methyl substituent at C-1. It has been isolated from the bark of Sickingia rubra, Symplocus racemosa, Passiflora incarnata, Peganum harmala, Banisteriopsis caapi and Tribulus terrestris, as well as from tobacco smoke. It is a specific, reversible inhibitor of monoamine oxidase A.