Three new naphthoquinones from the tubers of Sinningia mauroana

Three new naphthoquinones, 5,6,7-trimethoxydunnione (1), 6,7-dimethoxy-α-dunnione (2), and 5,6,7-trimethoxydunniol (3) were isolated from the tubers of Sinningia mauroana Chautems, together with eleven known compounds: 5-hydroxy-6,7-dimethoxy-α-dunnione (4), 6-hydroxy-7-methoxy-α-dunnione (5), 7-hydroxy-6-methoxy-α-dunnione (6), cedrol (7), tectoquinone (8), plantainoside A (9), calceolarioside A (10), calceolarioside B (11), sanangoside (12), allo-calceolarioside A (13), and conandroside (14). The known compounds 4, 7–9 and 11–13 are being reported for the first time in this species. Hexane, ethyl acetate and ethanol extracts were tested for antioxidant activity by the ORAC-FL method, and the antioxidant capacity was measured as trolox equivalent (TE). The ethyl acetate (8808 µg TE g−1) and ethanol (7911 µg TE g−1) extracts showed high antioxidant capacity, while the hexane extract displayed weak antioxidant capacity (860 µg TE g−1).