Isolation, structure elucidation, and cytotoxic evaluation of furanonaphthoquinones from in vitro plantlets and cultures of Streptocarpus dunnii

Two new furanonaphthoquinones, (3R)-7-methoxy-α-dunnione (5) and (3R)-6-hydroxy-7-methoxy-α-dunnione (6), along with the known (3R)-dunnione (1), (3R)-α-dunnione (2), (3R)-7-hydroxy-α-dunnione (3), and 1-hydroxy-2-methylanthraquinone (4), were isolated from in vitro cultures of Streptocarpus dunnii. The structures of compounds 5 and 6 were established by spectroscopic means. This is the first report of hydroxylated furanonaphthoquinones in a Streptocarpus species. Compounds 1-3 demonstrated cytotoxic activity against a range of breast Cancer and pancreatic tumor cell lines.