Dimeric naphthochromenes and other constituents of Sinningia allagophylla (Gesneriaceae)

Sinningia allagophylla, found in Brazil, Paraguay and Argentina, is used by the Brazilian population as diuretic, febrifuge, depurative, and tonic. We present the isolation of nine compounds (1-9) from its tubers, four of them being new: two dimeric naphthochromenes, allagophylldimer D (1) and allagophylldimer E (2); a coumarin, 6,8-dimethoxybenzocoumarin (3); and a naphthoquinone-derivative,  allagophyllone (4). The known compounds were identified as α-isodunnione (5), warmingiin A (6), warmingiin B (7), cleroindicin B (8), and cleroindicin C (9). All compounds were analyzed by 1D and 2D NMR, and HRMS spectra were recorded for the new compounds. Additionally, conformational analyses were carried on compounds 1 and 2. Compound 5 had been previously obtained only by synthesis, and its complete NMR data are presented here.