Nitro-phenanthrenes occurring in aristolochiaceae and other plants. They derive from stephanine (aporphines) by oxidative ring cleavage. The nitro group is a reactive alkylator (alkylating agents) that binds to biological macromolecules. Ingestion by humans is associated with nephropathy (nephritis). There is no relationship to the similar named aristolochene (sesquiterpenes).