An unusual C6-C6" linked flavonoid from Miconia cabucu (Melastomataceae)

Chromatographic fractionation of the methanolic extract from the leaves of Miconia cabucu Hoehne (Melastomataceae) afforded the first example of a C(6)-C(6") linked flavone dimer, 5-hydroxy-4',7-dimethoxyflavone-(6-C-6')-5'-hydroxy-3',4',7'-trimethoxyflavone as well as the known compounds, quercetin-3-O-alpha-l-rhamnopyranosyl-(2-->1)-O-beta-D-xylopyranoside, quercetin-3-O-alpha-l-rhamnopyranoside, myricetin-3-O-alpha-l-rhamnopyranoside, quercetin-3-O-beta-D-glucopyranoside, kaempferol-3-O-beta-D-(6'-coumaroyl)-glucopyranoside and gallic acid. Their chemical identities were established by application of NMR spectroscopic methods including 2D-NMR, as well as UV and ESI-MS analyses.