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).