Phenanthroid constituents from Aristolochia argentina

► Five phenanthrene derivatives were identified in Aristolochia argentina. ► A thio-aristolide and a 9-ethoxyaristolactam are reported for the first time. ► 9-ethoxyaristolactam I is reported for the second time from nature. ► The distribution of aristolactams and dioxoapophines in higher plants is discussed. ► Chemical links between the Aristolochiaceae and Annonaceae are suggested.