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).