Five new C-methyl flavonoids, the potent aldose reductase inhibitors from Matteuccia orientalis Trev.

Five new compounds, matteuorien, matteuorienin, and matteuorienate A (7), B (8), and C (9) were isolated together with five known compounds from the MeOH extract of the rhizome of Matteuccia orientalis Trev. The structures of these compounds were determined by the use of spectroscopic methods including two dimensional (2D)-NMR experiments and chemical methods, except for the configuration at the C-3"' of matteuorienate A (7), B (8), and C (9). Among them, matteuorienate A, B, and C showed very strong aldose reductase inhibitory activity. A structure-activity relationship study showed that a carboxyl group played an important part in aldose reductase inhibitory activity in these three compounds.